Project title:
2: Development of Predictive Modelling Capacity for Assessing
Comparative Strengths and Weaknesses of Intercrop Systems with
Respect to Productivity, Resource Use Efficiency and Labour
Requirements under Global Change (Climate, Labour, Economy)
st
1 Institution: Wageningen University
2nd Institution: Montpellier-SupAgro
Assoc. partner: China Agricultural University
Key words (4-6): Intercropping, productivity, resource use efficiency, labour, future,
modelling
Project description (max. 500 words):
Intercropping along the Yellow River in Gansu, China
Agriculture in China is still very small scale, with much of production being accomplished by
small holder families that crop only a few mu of land area (1 mu = 1/15 ha). Intercropping is
very important among the systems adopted by farmers. Intercropping systems cover
approximately one third of the agricultural land area of China, producing one half of the total
yield1.
There are many examples of complementarity and facilitation in intercrop systems and hence
these systems are usually very productive2,3. However, intercrop systems are complex to
manage, and they are difficult to mechanize. Due to economic development, labour prices in
China are rising rapidly, and a large proportion of the work force nowadays seeks work off
farm. The decreasing availability of labour puts intercropping under pressure. What would a
decreased adoption of intercropping mean for agricultural productivity and for agricultural
resource use efficiency? This question cannot be answered with the current knowledge.
A trustworthy intercrop productivity model would be needed to quantitatively explore the
added value of intercrops as compared to sole cropping for productivity and food security in
China.
There is presently very limited capacity for modelling intercrop productivity. Existing
platforms (e.g. APSIM4) do not account appropriately for planting densities, number of plant
rows per species, and other factors affecting crop spatial structure in intercrops. Therefore, an
upgrade in the capability for modelling eco-physiological performance of intercrop systems,
as compared to monocrop systems, is urgently needed.
An intercrop model will also support assessments of the use efficiency of water, nitrogen and
phosphorus. A valid assessment of water use efficiency is critical in view of the low
availability of water in the North China Plain, where most of the staple cereals wheat and
maize are produced.
Modelling productivity and resource use efficiency in mixed systems requires a careful
balancing of possibilities and needs. On the one hand, a valid assessment of intercrop
performance requires sufficient eco-physiological detail to quantify capture of light, water and
nutrient resources by component species correctly. On the other hand, the level of detail
should not be such that parameterizing the model becomes practically infeasible. We envisage
the development of a model of intermediate complexity that can be linked to an existing
framework, such as APSIM. The novel intercrop model will incorporate insights derived
from ongoing functional-structural modelling of plant-plant interactions5,6.
The desired outcome of the research is a valid intercrop model, parameterized for wheatmaize intercropping, as practiced on a large scale in Northern China. The model will be
parameterized and tested using existing data sets from China. We will address the necessary
level of complexity using mathematical techniques for model selection7,8. The model will be
used to develop scenarios and discuss future development pathways with stakeholders:
farmers, farmers’ organizations, NGOs, local and provincial governments, the Centre for
Technology Transfer of the Ministry of Agriculture, and the Centre for Chinese Agricultural
Policy of the Chinese Academy of Sciences.
Key research questions (2-4):
1. Is intercropping an ecologically and economically valid mode of crop production in
future China considering increasing population, changing diet, variable climate and
increasing price of labour?
2. What is the most parsimonious crop physiological model enabling credible, feasible
and trustworthy projections of crop production and resource use efficiency,
considering main staple foods: maize and wheat
Required competences: crop eco-physiology, agronomy, crop modelling, software
engineering
1
Zhang FS, Li L (2003) Using competitive and facilitative interactions in intercropping
systems enhances crop productivity and nutrient-use efficiency. Plant and Soil 248, 305-312.
2
Zhang L, van der Werf W, Zhang SP, Li B, Spiertz JHJ (2007) Growth, yield and quality of
wheat and cotton in relay strip intercropping systems. Field Crops Research 103: 178-188.
3
Li L, Li SM, Sun JH, Zhou LL, Bao XG, Zhang HG, Zhang FS (2007) Diversity enhances
agricultural productivity via rhizosphere phosphorus facilitation on phosphorus-deficient
soils. Proceedings of the National Academy of Science of the United States of America 104,
11192-11196.
4
Keating BA, Carberry PS, Hammer GL, Probert ME, Robertson MJ, Holzworth D, Huth NI,
Hargreaves JNG, Meinke H, Hochman Z, McLean G, Verburg K, Snow V, Dimes JP, Silburn
M, Wang E, Brown S, Bristow KL, Asseng S, Chapman S, McCown RL, Freebairn DM,
Smith CJ (2003) An overview of APSIM, a model designed for farming systems simulation.
European Journal of Agronomy 18, 267-288.
5
Vos J, Evers JB, Buck-Sorlin GH, Andrieu B, Chelle M, de Visser PHB (2010) Functionalstructural plant modelling: a new versatile tool in crop science. Journal of Experimental
Botany 61, 2101-2115.
6
Evers JB, van der Krol AR, Vos J, Struik PC. Accepted. "Understanding shoot branching by
modelling form and function." Trends in Plant Science.
7
Hilborn R, Mangel M. 1997. The ecological detectice – confronting models with data.
Princeton University Press 315 pp.
8
Bolker MM. 2008. Ecological Models and Data in R. Princeton University Press 396 pp.