introduction to plant and soil science sample

Introduction to Plant and Soil Science 2014 AG1008 —Teacher’s Edition AG3008 —Student Edition AG8008 —Teacher Resource CD

To order, call 800.654.4502 or visit www.okcimc.com

Introduction to Plant

and Soil Science

This free sample provided by CIMC www.okcimc.com 800.654.4502

Introduction to Plant and Soil Science (AG1008) is based on the Agriculture, Food and Natural Resources (AFNR) Career Cluster Content Standards. Students typically take this course after completing Introduction to Agriscience, also known as Agricultural Education I. The book is intended to build upon many of the concepts learned from Agriscience Explorations (AG1017) and Introduction to Agriscience (AG1001).

The student book and teacher books are both full-color. The teacher book is printed in a wrap-around format and includes suggested activities and websites. The teacher resource CD includes printable Assignment Sheets, Activity Sheets, and Lab Sheets, written tests in Word, PDF, and ExamView import formats, PowerPoints for each unit, project grading rubrics, and OSU Extension Fact Sheets.

Units include: World Agronomy Plant Structures and Functions Soil Formation and Use Plant Nutrition and Soil Fertility Tillage and Conservation Crop Improvement Seedling and Planting Practices Pest Management Harvesting and Marketing Sustainable Agriculture

Copyright 2014 Oklahoma Department of Career and Technology Education

CIM

CCIMCTeacher Edition

www.okcimc.com800-654-4502

AG100814-02356789

Introduction to Plant and Soil Science

Upfront

iii

Unit 1

World AgronomyCrop Characteristics • History of Crop Production • Plant Classification • Common Crops and Weeds • The Green Revolution

Unit 2

Plant Structures and FunctionsPlant Cell Organelles • Plant Growth Stages • Plant Vegetative Structures • Monocot and Dicot Vascular Systems • Plant Tissues • Reproductive Structures of a Plant • Major Plant Processes • Plant Responses to Stimuli • Legumes, Grains, Root and Tuber Crops

Unit 3

Soil Formation and UseSoil Formation • Soil Composition • Soil Particles and Texture • Soil Structures • Soil Profile • Soil Bulk Density • Soil Porosity and Water • Soil Moisture and Transpiration • Soil Chemistry

Table of

Contents Unit 4

Plant Nutrition and Soil FertilityNutrient Requirements of Plants • Acquiring Mineral Nutrients • Soil pH and Crop Production • Soil Test Reports • Using N-Rich Strips • Nutrient Cycling • Irrigation System Types

Unit 5

Tillage and ConservationHistory of Soil Conservation • Erosion • Erosion Management and Prevention • Artificial Drainage • Conventional and Conservation Tillage • Primary and Secondary Tillage • Conservation Programs

Unit 6

Crop ImprovementMendel’s Law of Genetics • Punnett Square • Methods of Crop Improvement • Genetically Engineered Crops • Plant Cloning • Plant Growth Regulators

1 77

31101

59 113

Free sample provided by CIMC www.okcimc.com

iv


175

Unit 7

Seeding and Planting PracticesSeed Quality and Selection • Germination and Live Seed • Dormancy • Seed Viability and Seed Vigor • Noxious and Common Weed Seeds • Sources of Agricultural Seeds • Planting Seeds • Equipment • Seeding Rate • Seeding Date and Depth

Unit 8

Pest ManagementPlant Pest Categories • Pest Damage • Methods for Controlling Pests • Pesticide Labels • Pesticide Safety Precautions • Plant Pesticides • Pesticide Application and Cost • Pesticide Resistance • Integrated Pest Management

Unit 9

Harvesting and MarketingHarvesting • Harvesting Methods and Equipment • Harvest Times • Harvesting Rates • Grain Storage • How Grain is Graded • Marketing Channels and Costs • Specialty Crops • Adding Value to Crops

129

147

Unit 10

Sustainable AgricultureWhat is Sustainability? • Organic Crop Production • Is Organic Agriculture Sustainable?

Glossary

Resources

197

205

215


1World Agronomy

• Describe crop characteristics and how crops are used.• Discuss the history of crop production.• Compare and contrast classification methods of agricultural

plants.• Identify agronomically important world crops and weeds by

common and scientific names.• Discuss the Green Revolution and its impact on agriculture.

agronomyangiospermannualbiennialbinomial

nomenclaturecarbohydratescenter of origincenter of productioncommon namecool-season plantscropsdomesticationgenusgreen manureGreen Revolution

gymnospermlipidslodgingMalthusian theorynonvascular plantsperennialphylogenetic treesplant taxonomyprimary producerssemi-dwarfshuttle breedingspeciessubspeciesvascular plantswarm-season plants

Key Terms

Objectives


2


Agronomy, the science of crop management and improvement, is a global business with a long history. Crops are plants that provide food, feed, fiber, and fuel. They are produced on every inhabited continent (except Antarctica) and were essential for the development of society. The ability to produce a reliable food source meant grain could be stored for a season or fed to livestock, which allowed previously nomadic peoples to establish cities. The ability to produce excess crops meant farmers had the ability to trade for goods or services, which allowed the development of economies.

Crop Characteristics?There are two primary characteristics that make a plant a crop. One characteristic is that the plant is domesticated. Through the process of domestication, a plant becomes genetically different from related wild plants, but the plant also becomes dependent on humans for its survival. Less than 10% of the world’s plant species have been domesticated as crops. The second characteristic is that the plant is used to meet peoples’ daily needs. It can be used either by the individual who grows the crop, or it can be sold to someone else who will use the crop.

Crops meet the daily needs of people by providing one of the “four F’s” – food, feed, fiber or fuel – and are the ultimate source due to their role in the ecosystem. Plants are called primary producers, which describes their ability to convert the solar energy in sunlight to chemical energy that is used by all other organisms. This energy conversion process is called photosynthesis.

Vietnamese women working in rice paddy Thinkstock Photos

The chemical energy produced in photosynthesis is stored as carbohydrates or lipids. Carbohydrate molecules are composed of carbon, hydrogen, and oxygen molecules arranged in different patterns. Sugars, like glucose, are the simplest carbohydrates. They are combined to make larger molecules, like amylose, which is important for supplying and storing energy, or cellulose, which is important for plant structure. Lipids are also primarily made of carbon and hydrogen. They are more energy-dense than carbohydrates and are important for

storing energy. When crops are harvested, they are processed to extract the carbohydrates and lipids. For example, wheat flour contains amylose, canola oil is made of lipids, and a cotton fiber is made of cellulose. The carbohydrates, lipids, as well as amino acids and vitamins stored in the plants, are the most important source of nutrients for people, whether the plants are eaten directly or indirectly through meat from animals that consumed the plants.


Unit 1 World Agronomy

3

History of Crop Production

Crop harvesting using a sickle Thinkstock Photos

Have you ever considered the history behind the wheat in your pasta or the corn in your tortilla chip? The food crops grown today have a long history. Gathering was the first step in domesticating many of the crops relied upon today. Historians believe that wheat was one of the first crops to be domesticated, about 10,000 years ago in the “Fertile Crescent”, near modern-day Turkey. Other civilizations developed additional cereal crops – for example, corn in Central America and rice in Asia. Today, these crops have spread around the world and represent the major sources of calories for people, with wheat being the most produced, most consumed cereal grain.

How did the development of these crops occur? Imagine a person walking through a grassy meadow foraging for grain to feed her family. What characteristics will she look for? Her past experience has taught her which plants produce tasty and nutritious seeds. She will likely be looking for plants that produce numerous seeds that are easy to collect, relatively large, and have not shattered (dropped from the plant). She may also be looking for seeds that are easy to make into food. Now, imagine that as she makes her way home some of her collection drops to the ground. These lost seeds may germinate and produce plants similar to the one from which they were harvested. Eventually, the foraging person learns to plant the seeds near the camp, establishing a crop and civilization. Increased crop yields meant excess food to trade for goods and other services in prehistoric civilizations. Even today, crops are an important part of the global economy.

Origin and Production

The place where a crop was first domesticated is called its center of origin. These regions are also called centers of diversity. The centers of origin theory was developed by a Russian scientist named Nikolai Vavilov. He developed this theory in 1926 and traveled around the world collecting plants. Unfortunately, because of the politics in his country, Vavilov was arrested in 1940 and died in prison in 1943. His scientific theory was later validated, and several Russian institutes and societies are named in his honor. One of the scientists who carried on the work begun by Vavilov was a man named Jack Harlan, who worked for a time at Oklahoma State University. In 1971, Harlan expanded Vavilov’s theory to better describe crop origins.


4


Corn varieties Thinkstock Photos

If a person was to travel to the center of origin of one of the important food crops, he or she would probably see a lot of variety in the crop. Consider corn as an example. Corn is believed to have been developed in central Mexico over 5,000 years ago. It was an important food source in the Mayan culture, which was dominant in the area between 1800 BC and 900 AD. The Mayans planted corn in combination with other native plants, like beans. The combination of corn and beans provided energy and protein that was the base of their diet. Corn was so important to the Mayans that they even had a corn god as a religious figure. Corn is still vital to the farmers of Central America. Many small farmers take a great deal of pride in the corn they grow. The seeds they plant today were passed down to them from their fathers and grandfathers. Farmers can tell you when and why their ancestors selected the seeds that developed the corn they grow today. Many individuals collecting plants with unique traits resulted in tremendous diversity in corn crops that exists today. In the United States, most of the corn eaten and fed to animals is yellow and wedge-shaped. Among small farmers in Central America, you are just as likely to find red, white, or blue corn being grown for food.

A center of production is a region where a crop is produced on a large scale. Modern centers of production are not the same as the centers of origin. For example, the U.S. is a center of production for soybean, corn, and wheat. But, these crops have centers of origin in China, Central America, and the Middle East. Countries that are centers of production are typically exporters of the crops they produce.

Centers of Origin

Centers of Production

Eastern US

Sahel Fertile Crescent

Ethiopia

China

New Guinea

West AfricaMesoamerica

Andes and Amazonia



5

Plant ClassificationThe practice of naming plants based on characteristics has occurred for thousands of years, and many of the same methods are used today. The science of categorizing plants is called plant taxonomy, which uses the hierarchical taxonomic scheme that groups plants at seven levels, with each level becoming more specific than the last. The levels are kingdom (broadest), phylum, class, order, family, genus, and species (most specific).

All living things are initially grouped into one of two scientific kingdoms – plant or animal. Each plant within the kingdom Plantae is further classified as vascular or nonvascular plants. Vascular plants, such as ferns, trees and flowering plants, have tubelike cells in their roots, stems and leaves that carry water and nutrients throughout the plant. Nonvascular plants do not have tubelike cells and take up water by osmosis via hairlike cells. Liverworts and mosses are examples of nonvascular plants.

Vascular plants are further classified by how they reproduce – seed or seedless. Seedless vascular plants, such as ferns, produce spores, while seeded plants include trees, crops and other flowering plants. Plants that produce seeds are further classified as angiosperms and gymnosperms. An angiosperm is a plant that produces seeds in a flower, and a gymnosperm, produces seeds in a cone, such as the pine tree. This classification continues until plants can no longer be separated. The most specific level of scientific classification is species with some species having several varieties.

Kingdom

Phylum

Class

Order

Family

Genus

Species

Plantae

Anthophyta

Monocotyledoneae

Poales

Poaceae

Zea

Zea mays

Corn TaxonomyPlants have two names – common and scientific – according to their classification. The common name is most often used to identify plants. However, common names vary from region to region. For example, the common name for corn in non-English speaking countries is maize. Because the difference of names can be confusing, scientists require a system of scientific naming known as nomenclature. Plant nomenclature, which is based on plant form and structure, results in universal names. Taxonomists use binomial nomenclature, a type of naming system using two Latin names, for the scientific names of plants. The first name is the genus or group name. Therefore, the genus of both corn and maize is Zea. All Zea genera (plural of genus) belong to a botanical family. Within a genus, plants may have different characteristics. To note these differences, plants have a second name to identify its species. Therefore, in the Zea genus, corn and maize have a species of mays. There are a number of varieties: Zea mays var. everta (popcorn) and Zea mays var. saccharata (sweet corn), to name a few.


6


A subspecies is another way to describe differences within a species. Both domesticated and wild plants can have subspecies, which is a subgroup of plants from a given location that have a unique characteristic but are not different enough to be a separate species. For example, the scientific name of the common sunflower is Helianthus annuus. Two subspecies of common sunflower are Helianthus annuus ssp annuus, which is the name given to plants that match the original description of the plant, or Helianthus annuus spp texanus, which describes slightly different plants that are found in Texas.

Pea plant pod Thinkstock Photos

Classifying crops is important because it allowsgeneralizations across similar species. There are multiple ways to categorize crops. Some categorization schemes are very precise and based on specific botanical characteristics; others are based on plant ecology or plant uses. Often a crop can be grouped in multiple categories, even within one categorization scheme. The most important characteristic for taxonomically classifying crops correctly is the flower. Flowers are important because they maintain certain characteristics no matter the growing environment.

Family-level classification is commonly used to describe relationships among crops and weeds. Most of the major crops we grow and eat come from two plant families: Poaceae (the grasses) and Fabaceae (the legumes). Grasses are important because the carbohydrates they contain are the main source of calories for people and animals, while the legumes are an important source of protein.

Taxonomic classification also considers the inheritance of traits. When scientists create graphics to describe inheritance, they are called phylogenetic trees. Phylogenetic trees are visual representations of how species are related to one common ancestor. The ability to study similarities in DNA has increased the precision of phylogenetic studies in recent years.

Other characteristics can be used to describe plants. For example, it is important to know a plant’s lifecycle – annual, biennial, perennial. Annual plants grow, produce seeds, and die in one growing season. They must reestablish from seeds in the next growing season. Biennial plants must reestablish from seed after two growing seasons. Perennial plants grow more than 2 growing seasons without starting from seeds. Many perennial and biennial plants have large roots or rhizomes where they store carbohydrates that are used to regrow after the first growing season.

It is also important to know what environment is best for plant growth. Some plants are considered warm-season plants, which means they grow best in warmer environments. In the United States, this means they grow mostly during the summer months and/or in the southern states. Warm-season plants cannot survive in cold weather. Other plants survive and even thrive in cooler weather. These are called cool-season plants, and they grow better in fall or spring and are more common in the northern states.



7

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8


Sometimes, it is useful to group crops according to characteristics other than their flowers or their DNA. The most common way to categorize crops is according to their agronomic use such as food, fiber and oil.

Cereal crops are some of the most important food crops in the world. They are grasses grown for their edible seeds. The seeds are usually high in carbohydrates. Examples of cereal crops include rice, wheat and corn.

Pulse crops are important sources of dietary protein for people. They are plants in the legume family harvested for their edible seeds, which have high concentrations of lipids in addition to proteins. Examples of pulse crops are peanuts, navy beans and chickpeas (garbanzo beans).

Root and tuber crops are harvested for their starchy below-ground storage organs. The plants use the carbohydrates for reproduction (in annual species) or over-wintering (in biennial or perennial species). Examples include potato, sweet potato, beets, and cassava, which is an important food crop in tropical countries.

Oil crops are harvested for their high-oil content seeds. After harvest, the seeds are crushed and the oil is extracted. Examples include canola, soybean and sunflower. Oil is also a byproduct of crops such as corn and cotton that are primarily produced for other purposes.

Cotton boll Thinkstock Photos

Fiber crops are used to produce textiles for clothing or other manufacturing purposes. Some fibers are part of the seeds (cotton) and other fibers are harvested from the stems or leaves (flax).

Forage crops produce large amounts of leaves and stems used to feed livestock. Forages are especially important for feeding ruminant animals (cattle, sheep). Most forages are either grasses or legumes. Examples include Bermuda grass and alfalfa.

Bioenergy crops have the potential to be used for biofuel production. Crops used to produce ethanol have high concentrations of carbohydrates, and crops used to produce biodiesel have high concentrations of oils. Examples of bioenergy crops are corn, switchgrass, soybean and jatropha, which is a small tree that grows well with very little water.

Cover crops are planted to protect from erosion or improve the soil quality by adding nutrients and/or organic matter. Sometimes a crop like rye is planted and then killed using herbicides before planting a crop like corn or soybean. Other times, a crop like clover is tilled into the soil; when this is done the crop is called a green manure. One crop being developed specifically for use as a cover crop is the tillage radish. It is planted in the fall and the large roots grow over the winter. When the roots decay in the spring, they improve soil quality.



9

International Development

Agronomist

CAReeR SPOTlIGHT

Many companies and non-profit organizations have career opportunities for agronomists and crop scientists who are interested in traveling around the world. One place to look for work as an international development agronomist is with centers that are part of the Consultative Group on International Agricultural Research. The first of these centers to be established was CIMMYT, the International Maize and Wheat Improvement Center in Mexico, where Norman Borlaug began the Green Revolution. Now, there are fifteen centers located around the world.

An international development agronomist works in developing countries to help improve the lives of people who live there. You would conduct research to determine the best ways to produce crops in the region in which you work. Then, you would share information you learn with the people living in the area.

To be an international development agronomist, you will probably need to complete a master’s degree or doctoral degree in crop breeding or management. You will also need to get experience traveling internationally. Salaries for international development agronomists depend on their previous experience, but start at about $50,000 plus benefits.

Sources

www.CGIAR.org

Thinkstock Photos


www.CGIAR.org

10


Common Crops and WeedsThe earth is inhabited by a multitude of plant species and varieties. Some are common to many regions, and others may only exist in small, remote areas. Producers should be familiar with the crops most successfully grown in their particular region and climate, as well as the weeds most prevalent. The identification knowledge will help producers in treating weed pests as well as producing crops with the highest yield.

All crops and weeds have specialized characteristics. Some crops are high oil-producing plants making them a valuable oil source. Other crops are needed for their nutrient value making them important for human and livestock consumption. Weeds on the other hand can be detrimental to a producer if not controlled. It is important to have a basic knowledge of common crops and weeds, and to be able to identify these plants.

Cereal Crops

Barley

Thinkstock Photos

Hordeum vulgare subsp. vulgare

Barley is a cool-season, annual cereal grain native to southwest Asia. It is believed that barley is a crop even older than wheat. Much of the barley grown in the United States is used for malt, which goes into breakfast shakes and alcoholic drinks. It is also used as a forage and cover crop.

Copyright Samantha AmbroseOklahoma State University

Seeds: tan in color, size varies by variety, lemma and palea still attached, wrinkled lemma, awns

Flowers: spike inflorescence

Leaves and grows upright, rolled vernation, sheath Stems: overlapping and hairless, leaf keeled with smooth margins, long clasping

auricles, short membranous ligule

Roots: fibrous



11

Corn

Thinkstock Photos

Zea mays

The plant Americans know as corn is commonly called maize throughout the rest of the world. There are several subspecies of corn; the most widley cultivated is dent corn, or field corn. This corn is primarily used for animal feed or ethanol production. Most Americans are more familiar with the better-tasting subspecies, sweet corn. Corn is a warm-season annual grass native to Central and South America.

Photo by Travis Bradshaw

Seeds: wedge-shaped, dent on end opposite (dent corn only), usually yellow in color, can be white, blue, or red

Flowers: imperfect, male flowers in panicle at top of plant (tassel), female flowers in spike (ear) about 6 nodes below the top of the plant

Leaves and thick stem (stalk) grows upright and often covered Stems: with hairs, leaves opposite with hairs, may have short membranous ligule, no auricles

Roots: fibrous, no rhizomes, no stolons

Grain Sorghum

Thinkstock Photos

Sorghum bicolor

Grain sorghum is a warm-season grass native to Africa. One very popular variety of grain sorghum in the United States is called milo. Grain sorghum can be used similarly to corn in animal feed and ethanol production. There are numerous other types of sorghum that are used as forages or are weeds.


Seeds: round with pointed attachment point, white to dark brown in color

Flowers: inflorescence a compact panicle

Leaves and stem upright, may tiller at base, leaves with Stems: prominent midrib, may have waxy covering,

short membranous ligule, no auricles



12


Oats

Thinkstock Photos

Avena sativa

Oat is a cool-season annual cereal crop native to Europe and the Middle East. Oat is often fed to livestock, but the discovery of its ability to lower cholesterol has increased its popularity as human food. It is sometimes grown for forage in the southern United States. There are both winter and spring varieties, which are adapted to different climates.


Seeds: 8-9 mm long, light tan in color, lemma and palea stay attached, lemma is smooth, straight awns

Flowers: panicle inflorescence

Leaves and stems upright with tillers, rolled vernation, Stems: overlapping sheath margins, tall toothed

rounded membranous ligule, no auricles

Roots: fibrous, no stolons or rhizomes

Rye

Thinkstock Photos

Secale cereale

Rye is a cool-season annual cereal native to southwestern Asia and northern Europe. Because rye flour doesn’t contain enough gluten to make bread, it is mixed with wheat flour. Using rye flour results in darker, more dense bread than using wheat flour alone. The plant is also used as a forage or cover crop.

Copyright Samantha Ambrose Oklahoma State University

Seeds: gray-green in color, seed coat has small scales

Flowers: long, narrow spike with toothed glumes

Leaves and stems upright with tillers, rolled vernation, Stems: sheath with overlapping margins, short

auricles, rounded, jagged membranous ligule

Roots: fibrous, no stolons or rhizomes



13

Wheat

Copyright Kaitlyn Nelson Oklahoma State University

Triticum aestivum

Wheat is a cool season cereal crop native to the Middle East and Europe. Wheat is primarily used for baked goods, but it is a highly valued forage commonly grazed in the southern plains. There are six classes of wheat, grouped according to characteristic of the seed and when planted. Durum wheat is grown in the northern plains, planted in the spring, and has a very high protein content that makes it good for pastas. Hard red spring wheat is also grown in the northern plains and planted in the spring. It has a high protein content and a dark bran. It is primarily used for bread. Hard red winter wheat is also used for bread and has dark bran, but it is grown in the southern plains and planted in the fall. Hard white wheat has high protein content and light bran. It is used to make “whole wheat white” bread because the bran does not have the same chemistry as the red wheats. Soft red winter wheat is planted in the fall throughout the eastern United States. It has a low protein content, which means it is not good for making bread. Instead, it is used for making cakes, cookies, and crackers. Soft white wheat is also used for baked goods rather than bread. It is has low protein content and light-colored bran, and is primarily grown in the northwestern United States.


Seeds: 6 mm long, orange (red classes and durum wheat) or tan (white classes) in color with a prominent brush on the end opposite the endosperm, visible crease and cheeks

Flowers: inflorescence a thick spike

Leaves and stems upright with tillers, rolled vernation, Stems: leaf sheath with overlapping margins, short hairy

clasping auricles, short rounded membranous ligule

Roots: fibrous, no stolons, no rhizomes


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Rice

Thinkstock Photos

Oryza sativa

Rice is a warm-season annual grass native to Asia. Along with wheat, it is one of the most important sources of calories for people, particularly in developing countries. A primary food in many parts of Asia, rice makes up anywhere between 55% and 80% of the caloric intake in countries such as Bangladesh, Cambodia, Indonesia, Laos, Thailand and Vietnam where the average person eats up to 300 lbs. of rice a year. Of the world’s 520 million metric ton crop grown worldwide, 95% is consumed in Asia and grown within 5 miles of where it is consumed.


Seeds: white seeds do not thresh free of glumes which are gold in color with vertical ridges and a curve near the attachment point

Flowers: inflorescence is an open panicle

Leaves and stems upright with tillers, hairy sickle-shaped Stems: ligule, short auricles


Pulse Crops

Peanuts

Thinkstock Photos

Arachis hypogaea

Peanut is a warm-season annual legume native to South America. It is primarily grown for the seeds, but can also be used for hay. There are three types of peanuts grown in the United States. Runner, which is used for peanut butter and is the most widely grown; Spanish, which is used for candy production and are grown primarily in the southwest; and Virginia, which are roasted and sold in the pod. There are also perennial, rhizotomous varieties that are grown for forage.



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Seeds: tan, covered by loose red seed coat, enclosed in tan pod with netted veins covering the surface

Flowers: yellow flowers with five petals – a banner, two wings, and a two petals fused to form a keel in leaf axils, produce a stalk which grows into the ground where the pod forms

Leaves and branching stems grow low to the ground, Stems: leaves alternate, pinnately compound with two

pair of opposite leaflets, surface hairless, margin entire

Roots: shallow taproot

Oil Crops

Canola

Thinkstock Photos

Brassica napus

Canola is a cool-season annual crop native to the Himalayas. It is a special form of a crop called rapeseed that is edible because it has been bred to be lower in certain fatty acids and toxins. Canola has been used as a winter forage in Europe but is not used for forage in the United States. There are both spring and winter canola varieties. Winter canola varieties have become an important crop in the southern plains of the United States since about 2005. When Oklahoma farmers plant canola, it improves the quality of wheat crops because farmers can easily control weedy grasses that cannot be controlled in wheat.


Seeds: round, about 2 mm in diameter, brown to black, formed in long, thin pods with beaked tips

Flowers: four yellow petals

Leaves and no hairs, lower leaves clasping petioles with fewer Stems: lobes, upper leaves sessile

Roots: taproot, no rhizomes, no stolons


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Sesame


Sesamum indicum

Sesame is a warm-season annual plant native to India. It is grown for its edible seeds and oil. Sesame seeds produce relatively large quantities of high quality oil. In fact, Thomas Jefferson believed it to be the best substitute for olive oil that could be produced in the United States.


Seeds: ovate, flattened, white yellow or black in color

Flowers: white to pink, bell-shaped flowers grow in leaf axils

Leaves and stems upright, branched or unbranched, leaves and Stems: stems hairy, lower leaves opposite, upper leaves

alternate, serrate or entire margins

Roots: deep taproot

Sunflowers

Thinkstock Photos

Helianthus annuus ssp. macrocarpus

Sunflower is a warm-season annual plant native to North America. It is grown primarily for its oil, but some varieties are used in snacks (confectionary varieties). Cultivated sunflowers are the same genus and species as wild sunflowers.


Seeds: gray in color, enclosed in hard covering that is ovate and either black (oil varieties) or white with black stripes (confectionary varieties)

Flowers: inflorescence is a head with yellow ray flowers and reddish-brown disk flowers, hairy, overlapping bracts beneath head, larger than common sunflower

Leaves and stems upright, branched, covered in hairs, lower Stems: leaves opposite, upper leaves alternate, cordate,

rough, hairy

Roots: deep taproot



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Soybeans

Thinkstock Photos

Glycine max

Soybean is a warm-season annual legume native to Asia. Soybean production first became popular for forages in the southeast United States. Since World War II, production has shifted to the Midwestern United States to focus on the seeds, which contain large amounts of oil. The seeds are also an important protein source in animal feed, and the plant is sometimes used for hay.


Seeds: round with prominent hilum, often yellow in color but may be black or reddish-brown

Flowers: small legume flowers, white or purple in color grow in leaf axils

Leaves and stems upright and branched, leaves and stems Stems: covered in brownish hairs, trifoliate leaves pinnately

compound with round or ovate leaflets

Roots: taproot

Fiber Crops

Cotton

Thinkstock Photos

Gossypium hirsutum

Cotton is a warm-season annual crop native to Asia and South America. Wild cotton is a perennial plant. Cotton is grown in the southern United States for the fibers that form around the seed (bolls). It is the most produced fiber crop in the world.


Seeds: ovate, slightly curved, dull brown to black in color, covered with lint

Flowers: large flowers, 5 petals, white in color until pollinated, surrounded by 3-4 large fringed bracts

Leaves and leaves alternate with 3-5 lobes, stipules at base of long Stems: petiole, stem with black spots and hairs

Roots: deep taproot


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Forage Crops

Alfalfa


Medicago sativa

Alfalfa is a cool-season perennial forage crop native to the Middle East. It is a legume crop sometimes called the “Queen of Forages” because it produces very nutritious forage. It regrows from the base of the stem using energy stored in large roots. The name alfalfa comes from Arabic for “horse power”, which acknowledges alfalfa’s importance as a source of energy for horses during wars in ancient societies in the Middle East.


Seeds: small (about 2 mm long), kidney shaped, hilum located in notch, smooth, dull surface, orange to olive in color

Flowers: legume flower (five petals – a banner, two wings, and a two petals fused to form a keel), purple to blue in color

Leaves and grows upright, three leaflets, terminal leaflet on Stems: longer petiole (pinnately compound), serrations on

upper 1/3 of leaflet margin, pointed stipules with serrated margins located at leaf axils

Roots: large, fleshy taproot grows up to 15 feet deep

Bermuda Grass

Thinkstock Photos

Cynodon dactylon

Bermuda grass is a warm-season perennial forage crop native to southeast Africa. It has average forage quality but is very persistent and regrows from stolons and rhizomes. Because it quickly produces a large amount of forage, Bermuda grass is an important forage for hay in the southern United States. Unimproved Bermuda grass is considered a weed in row crops.



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Seeds: 2 mm long, light tan lemma and palea, boat-shaped lemma

Flowers: raceme inflorescence with 3-6 finger-like spikelets, seeds produced only on one side of spikelets

Leaves and grows low to the ground, folded vernation, sheath Stems: overlapping, hairs at base of leaf, membranous ligule

with fringe of hairs, no auricles

Roots: fibrous, also has stolons and rhizomes

Weeds

Common Cocklebur


Xanthium strumairum

Common cocklebur is a summer annual weed native to Eurasia and Central America. One identifying characteristic is the distinctive odor emitted when the plant is crushed.


Seeds: about 1 cm long, oval with hooked spines, brown to black in color, hairs at base of spines, two seeds within each bur

Flowers: imperfect flowers

Leaves and branched stems with purple to brownish-black Stems: spots, leaves alternate, long petioles, irregularly toothed, rough on both surfaces

Roots: taproot, no stolons or rhizomes


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Common lambsquarters


Chenopodium album

Common lambsquarters is a summer annual weed native to Europe and Asia. It was historically harvested as a wild vegetable, often confused with pigweeds.


Seeds: round with notch in one edge, about 1.2 mm long, one side flat and one convex, black in color with somewhat shiny surface, often enclosed in a grayish tan seed coat

Flowers: small, green flowers in spikes at end of branches and leaf axils

Leaves and stems grow upright, red/purple streaks, leaves Stems: opposite, triangular and coarsely toothed (lower) or

with indented to entire margins (upper), upper leaf surface covered with white particles

Roots: short, branched taproot, no stolons or rhizomes

Common Ragweed

Thinkstock Photos

Ambrosia artemisiifolia

Common ragweed is a warm-season annual native to North America. A related species, giant ragweed, is also found throughout the United States. Pollen produced by ragweed is a common cause of “hay fever”.


Seeds: about 3.5 mm long, brown in color, with a spike that extends from the top of the seed and is surrounded by 5-8 smaller projections, giving the seed a crown-like appearance

Flowers: imperfect, small yellow-green in racemes at end of stems (male flowers) or in the axils (female flowers)

Leaves and leaves opposite on lower stem, alternate on upper stem, Stems: leaves deeply lobed or dissected, stems upright with

little branching leaves and stems covered with short white hairs

Roots: shallow taproot, no stolons or rhizomes



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Common Sunflower

Thinkstock Photos

Helianthus annuus subsp. annuus and others

Common sunflower is a warm-season annual weed that is native to North America. It is the same genus and species as cultivated sunflowers.

Steve Hurst @ USDA-NRCS Plants Database

Seeds: wedge-shaped or ovate, about 6 mm long, grayish or brown with black mottles or zig-zags

Flowers: inflorescence is a head with yellow ray flowers and reddish- brown disk flowers, hairy, overlapping bracts beneath head, smaller than cultivated sunflower

Leaves and stems are upright, branched, covered with stiff white Stems: hairs, lower leaves opposite, most leaves alternate,

triangular or heart-shaped with three prominent veins, serrated margins, hairy and rough on both upper and lower surface

Roots: taproots

Hairy Vetch

Jennifer Anderson @USDA-NRCS PLANTS Database

Vicia villosa

Hairy vetch is a winter-hardy annual legume native to Europe and western Asia. It is crop rotated for its nitrogen-fixing properties. Seeds do tend to shatter early in the growing season leading to weeds remaining in the field when crops are rotated, especially problematic for wheat crops.

Steve Hurst @ USDA-NRCS PLANTS Database

Seeds: round, mixture of black, brown and gray

Flowers: long and small, at least 8 purpled flowers in a raceme

Leaves and compound leaves and narrow Stems: leaflets, end in tendrils, stems grow from 2-4 inches in length

Roots: taproot that extends to almost 1 m


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Horseweed

Photo by Teun SpaansWikipedia Commons

Conyza canadensis

Horseweed is an annual weed native to North America. It has become a troublesome weed in no-till crop production systems. Glyphosphate resistant plants are prevalent throughout the United States.

Photo by Teun SpaansWikipedia Commons

Seeds: about 1 mm long, white pappus, about 2 mm long, oblong with narrow base, light tan colored with short silky white hairs

Flowers: inflorescences small heads with yellow disk flowers surrounded by white to light pink ray flowers

Leaves and stem upright, covered in hairs, seldom branches; Stems: leaves alternate, lanceolate, toothed near end

with fine white hairs near margin; leaves crowded on stem, upper leaves smaller that lower leaves

Roots: short taproot, no stolons or rhizomes

Johnsongrass


Sorghum halapense

Johnsongrass is a warm-season perennial weed native to the Mediterranean region. It was introduced in the southern United States as a potential forage grass. It is a noxious weed and can accumulate levels of prussic acid and nitrates toxic to grazing animals.


Seeds: black to reddish-brown or light tan in color, about 2.5 mm long, long ridges, knobbed rachilla

Flowers: inflorescence open panicle with lots of branches

Leaves and grows upright, rolled in the bud, sheath overlapping, Stems: leaves usually hairless with prominent white mid-vein,

tall rounded membranous ligule, no auricles

Roots: fibrous, has many rhizomes



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Jointed Goatgrass

Matt Lavin,Bozeman, Montana, Author Wikimedia Commons

Aegilops cylindrica

Jointed goatgrass is a cool-season annual grass native to Europe. It is very difficult to control in winter cereal crops, like wheat.


Seeds: cylindrical, tan, about

Flowers: spike inflorescence with 2-5 cylindrical seeds

Leaves and upright stems, hairs on Stems: margins of sheat, stiff

hairs on leaf margin, membranous ligule,

short auricles


large Crabgrass

Rasbak, Author Wikimedia Commons

Digitaria sanguinalis

Large crabgrass is a warm-season annual plant native to southern Africa. It is considered a weed in many row crops but can be used as a forage crop.


Seeds: approximately 3 mm long, tan in color, flattened with three veins on one side, hairy

Flowers: raceme inflorescence with finger-like spikelets

Leaves and tends to grow low to the ground, are rolled in the Stems: bud, the sheath is flattened with overlapping

margins, leaves are covered with short silky hairs on both upper and lower surface, membranous toothed ligule, no auricles

Roots: fibrous, forms adventitious roots at nodes, also has stolons


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Pennsylvania Smartweed

Frank Mayfield, Author Wikimedia Commons

Polygonum pensylvanicum

Pennsylvania smartweed is a warm-season annual plant native to North America. Smartweeds tolerate wet conditions and are important food sources for waterfowl, like ducks.


Seeds: rounded, flattened with pointed tip, about 3 mm long, black to dark brown in color, pale at the point of attachment, smooth and very glossy

Flowers: small flowers without petals, pink to white in color arranged in spike inflorescence at ends of stems

Leaves and leaves alternate, elongated and eliptical, often Stems: with purple marking on upper surface, stems

reddish tint, ochrea and nodes

Roots: shallow taproot, no stolons, no rhizomes

Redroot Pigweed


Amaranthus retroflexus

Redroot pigweed is a warm-season annual weed native to central America. It is one of many weeds in the amaranth family which have similar characteristics. Amaranths can be especially problematic due to their very high seed production and the numerous herbicide resistant plants that exist.


Seeds: ovate, about 1 mm long, black, shiny surface, notch at hilum

Flowers: small, green with stiff bracts in crowded spikes at end of branches or axils

Leaves and alternate, ovate with wavy margins, hairy Stems: with prominent veins on lower surface

Roots: tap root, no stolons or rhizomes



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Silverleaf Nightshade

Jerry Friedman Wikipedia Commons Image

Solanum elaeagnifolium

Silverleaf nightshade is a warm-season perennial native to southwestern United States and northern Mexico. It is a noxious weed and can poison livestock and humans if eaten. Nausea, abdominal pain, labored breathing, weakness and paralysis are some of the symptoms of poisoning.

Steve Hurst @ USDA-NRCS PLANTS Database

Seeds: green striped, round, about 1 cm in diameter

Flowers: lavender, star-shaped flowers with yellow centers, 5-pointed petals

Leaves and leaves alternate, silvery foliage, stems have Stems: slender yellow spines

Roots: deep vertical roots and creeping horizontal roots

Tall Morning-Glory

Patafisik, Author Wikimedia Commons

Ipomoea purpurea

Tall morning-glory is a warm-season annual native to Central America. It is one of several species of morning-glory found in the United States.


Seeds: shaped like orange slices, about 5 mm long, horseshoe shaped hilum, gray to brownish black in color

Flowers: white to purple funnel-shaped flowers with short green sepals in clusters of three or more

Leaves and vining/twining stem, hairy; leaves Stems: heart shaped, alternate, older leaves overlap

at base, hairs lie flat against upper leaf surface

Roots: taproot, rhizomes


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Velvetleaf


Abutilon theophrasti

Velvetleaf is a warm-season annual native to Asia and India. Its seeds can live in the soil for many years, making it difficult to eradicate. It is used as a fiber crop in some parts of the world.


Seeds: heart-shaped, about 3 mm long, notch on one lobe, thicker at edges than in center, covered with short hairs, grayish brown in color with rough texture

Flowers: five orange-yellow petals, develop in leaf axils

Leaves and stems grow upright with few branches, leaves Stems: and stems covered with short soft hairs, leaves

cordate with entire or irregularly toothed margins

Roots: taproot, no stolons, no rhizomes

Wild Oat

Kurt Stueber, Author Wikimedia Commons

Avena fatua

Wild oat is a cool-season annual grass native to Europe and the Middle East.


Seeds: twisted, angled awn, 3-4 cm

Flowers: drooping panicle

Leaves and: stems grow upright, Stems: rolled vernation, large

white torn membranous ligule, no auricles, leaves may be hairy near base

Roots: fibrous, no stolons, no rhizomes



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Yellow Foxtail


Seteria glauca

Yellow foxtail is a warm-season annual weed native to Europe and Asia. Young leaves may be grazed by livestock. Seeds are important sources of food for wild birds.


Seeds: about 2.5 mm long, yellowish green to black in color, lemma has wavy ridges that run across the seed, palea covers less than half the length of the seed

Flowers: dense spike with yellow to red bristles

Leaves and grow upright, rolled in the bud, no hairs on Stems: margin of leaf sheath, long, twisted hairs near base

of leaf blade, ligule fringe of short hairs, no auricles

Roots: fi brous, no stolons or rhizomes

Yellow Nutsedge

Blahedo, Author Wikimedia Commons

Cyperus esculentus

Yellow nutsedge is a warm-season perennial native to the Mediterranean. It is also known as chufa, which is eaten in Africa, Western Europe, and the Mediterranean. A similar species, purple nutsedge is also present throughout the United States.


Seeds: form in a small (1.5 mm) three-sided fruit

Flowers: small flowers are in spikelets at the end of the stems

Leaves and leaves flat and shiny, yellow-green in color, Stems: come from base of stem in groups of three to

make a triangular sheath around stem

Roots: fibrous, produces tubers (1-2 cm long) that are round and ridged at the end of rhizomes


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The Green RevolutionMany technological advances occur as agricultural systems develop. Early advances such as irrigation and tools increased the efficiency of crop production. Early agriculturalists also devised crop rotations and used manures for fertilizers. The development of technology resulted in greater crop yields.

Even so, in 1798, Thomas Malthus published “An Essay on the Principle of Population.” In this document, he established what came to be known as the Malthusian theory, which says the human population will outgrow the ability to produce food because populations increase exponentially and the ability to produce food is limited by available land. Fortunately for us, Malthus has not been proven right. In fact, the number of food-insecure people on Earth is decreasing. Two things have happened to keep the population size within the limits that can be supported by existing food. First, the population in developing countries has stabilized. This means the total population has not increased as rapidly as Malthus predicted. Second, the ability to produce food has increased more rapidly than Malthus predicted. One of the sources of increased food production is the life’s work of Norman Borlaug.

Dr. Norman Borlaug Photo courtesy of USDA-FAS

Dr. Borlaug was hired in 1944 to oversee a project to breed improved wheat varieties. The wheat farmers grew during the 1940’s was much taller than the wheat farmers grow today. Because it was so tall, the wheat was susceptible to falling over (lodging), and was inefficient to grow because much of the nutrients the plant consumed were used to grow the stems and leaves, which are not directly useful for producing food. Dr. Borlaug found dwarf wheat from Japan that he bred with the commonly grown tall wheat. This produced the semi-dwarf wheat varieties grown today, which are more efficient to produce and less susceptible to lodging. Another unique practice of Dr. Borlaug’s was the use of a method called shuttle breeding. This meant he was using two locations, one in a coastal area and one in the mountains, to conduct his breeding experiments. Because he used two locations, he was able to create varieties of wheat that were adapted to a wide range of environmental conditions. This allowed the wheat Dr. Borlaug developed in Mexico to grow well in faraway places like India. These new varieties were also resistant to significant diseases.

Dr. Borlaug also helped farmers learn the best practices for growing wheat, including fertilizer use. He brought scientists to Mexico for training, who returned to their homes to help improve agriculture. All of this work resulted in a drastic increase in food production around the world, specifically in places like Mexico and India. This time period is called the Green Revolution. Because of his efforts, Dr. Borlaug is called the “Father of the Green Revolution” and is the only agriculturalist to win a Nobel Peace Prize, which he received in 1970. But, not every country



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benefited from the Green Revolution. Specifically, countries in Africa did not improve their crop production. Dr. Borlaug continued to work with these countries to produce more food until the time of his death in 2009.

Other advances that greatly impacted agriculture and increased yields were mechanization during the industrial revolution (around 1800), the development of synthetic fertilizers (Fritz Haber was awarded the Nobel Prize in Chemistry in 1918 for developing the process that converts nitrogen gas to ammonia), the development of hybrid corn varieties by Henry Wallace in 1924, the development of 2,4-D as the first selective herbicide in 1944, and the development of transgenic crops in the 1980’s.

These advances in agricultural technology, specifically the work of Dr. Borlaug, are credited with saving the lives of billions of people. Many of the Green Revolution lessons are important for modern agriculture. For example, using fertilizers and irrigation to help plants reach their maximum genetic potential, and using multiple locations to develop crops that grow well in many places. However, there are people who believe that Dr. Borlaug’s systems of producing wheat are not sustainable for the future.

Unit SummaryPlants are primary producers in an ecosystem. Crops are domesticated plants which are harvested so their stored energy can be used to provide food, feed, fiber or fuel for people. Crops developed about 10,000 years ago in centers of origin, also called centers of diversity. Modern production occurs in regions that are away from the centers of origin.

Categorizing and identifying plants are important aspects of plant science. The branch of science that studies plant classification is called plant taxonomy. Taxonomists use the hierarchical classification system to categorize and describe plants. The most specific way to describe a plant is by its scientific name, but knowing a plant’s family is very helpful, too. Some important plant families include poaceae, fabaceae, asteraceae, brassicaceae, and solonaceae. Plants can also be categorized according to their life cycle and the environment to which they are adapted. Agronomic use categories, such as cereal crop, pulse crop, forage crop, fiber crop, and cover crop, are also important to know.

Properly identifying plants requires knowledge of plant characteristics, such as leaves, stems, roots, and seeds. It is also helpful to know the life cycle and environmental adaptation. Knowing a few unique characteristics of a plant will help you identify them.

Many technological advances have led to increased crop production. The Green Revolution was a period of rapidly increasing yields of crops, especially wheat, due to improved varieties and agronomic practices introduced by Norman Borlaug.


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Unit Review1. What is agronomy?2. What role do plants fulfill in an ecosystem?3. How is energy stored in plants?4. What are two characteristics of crop plants?5. What happens to a plant when it is domesticated?6. How are a crop’s center of origin, center of diversity, and center of production related?7. What are the proposed centers of origin for wheat, rice, and corn?8. What is plant taxonomy?9. What are the levels in hierarchical plant classification, in order from least specific to most

specific?10. What are some other ways (besides hierarchical classification) that plants can be

categorized?11. What are characteristics of annual, biennial, and perennial crops? 12. What are characteristics of a warm-season and cool-season plant? 13. What are the predictions of the Malthusian Theory? 14. Why have the predictions of the Malthusian Theory not come true?15. What was the Green Revolution? 16. Who is credited with facilitating the Green Revolution? 17. What are two new characteristics of the wheat introduced during the Green Revolution?18. What region did not benefit from the Green Revolution?


introduction to plant and soil science sample

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