powerpoint-presentatie 4/session iii - estuary...title powerpoint-presentatie author martin brinkman...

Framework for yield gap analysis in grasslands

René Schils, Mats Höglind, Jantine van Middelkoop, Gertjan

Holshof, Koos Verloop, Bert Rijk, Gerrie van de Ven, Wim van

den Berg, Jan Rinze van der Schoot, Martin van Ittersum

Framework for yield gap analysis in grasslands

Background on yield gap concept

Yield gaps in grassland

Examples for the Netherlands and Norway

2

Background on yield gap concept

Challenge to keep production on track with demand

Identify regions with unlocked yield capacity

Lagging attention for grasslands

● Grass is an internal farm product

● Animal farmers focus on their animals

● Methodological complexity

Theoretical production ecology

4

Reducingfactors

•weeds•diseases•pests•pollution

Limitingfactors

•water•nutrients

Definingfactors

•Climate•CO2•variety

CR

OP

YI

EL

D

LimitedPotential ActualYi

eld

Gap

Van Ittersum & Rabbinge, 1997

Yie

ld G

ap

Quantifying...

• Benchmarks

YP Potential yield

YW Water-limited yield

YN Nitrogen-limited yield

YWN Water- and nitrogen-limited yield

• Farm yields

YA Actual yield

• Potential for improvement

YG Yield Gap

5

Global Yield Gap Atlas

Rainfed wheat

6

www.yieldgap.org

Yield gaps – general approach

Data

Daily weather

Soils

Crop types and management

Varieties

Experimental yields

Actual farm yields

7

Identify unique zones

Agro-climatic conditions

Cropping systems

Quantify yield levels

Simulate YP, YW, YN, YWN

Calculate YA, YG

Yield gaps – additional challenges grasslands

Diversity in grasslands

● Function

● Botanical composition

● Management

Definition of productivity

● Gross yield in field – Net yield at field gate – Net animal intake

● DM yield – Digestible energy – Crude protein

Actual yield assessment

● Spatial and temporal data availability

● Definitions of grassland types

● Methods to estimate yields

8

Yield gaps – Netherlands and Norway

Netherlands

Intensive dairy farming

975.000 ha

Mainly perennial ryegrass

2 silage cuts / 4 grazings

Empirical model (GRASS2007)

9

Norway - Rogaland

Dairy, beef and sheep farming, various intensity

100.000 ha

Timothy or perennial ryegrass

3 silage cuts / 1 grazing

Process model (BASGRA)

Yield gaps - summary

10

Spatial variation

11

YA for different regions in NorwayYW for different soil types in SE Norway (LINGRA; Persson et al., 2015)

Sensitivity to grassland management

12

Simulated (GRASS2007) YW with increasing cutting frequency

Calculated YA of grass for ~2000 farms in Nutrient Cycling Assessment projects

Framework for

yield gap

analysis in

grasslands

13