Biomass production of annual crops is often directly proportional to the
amounts of radiation intercepted, water transpired and nutrients taken
up. In many places the amount of rainfall during the period of rapid
crop growth is less than the potential rate of evaporation, so that
depletion of stored soil water is commonplace. The rate of
mineralization of nitrogen (N) from organic matter and the processes of
nutrient loss are closely related to the availability of soil water.
Results from Kenya indicate the rapid changes in nitrate availability
Nutrient supply has a large effect on the quantity of radiation
intercepted and hence, biomass production. There is considerable scope
for encouraging canopy expansion to conserve water by reducing
evaporation from the soil surface in environments where it is frequently
rewetted, and where the unsaturated hydraulic conductivity of the soil
is sufficient to supply water at the energy limited rate (e.g. northern
Syria). In regions with high evaporative demand and coarse–textured
soils (e.g. Niger), transpiration may be increased by management
techniques that reduce drainage.
Increases in atmospheric [CO<sub>2</sub>] are likely to have only a
small impact on crop yields when allowance is made for the interacting
effects of temperature, and water and nutrient supply.
Gregory, P.J.; Simmonds, L.P.; Warren, G.P. Interactions between plant nutrients, water and carbon dioxide as factors limiting crop yields. Philosophical Transactions B: Biological Sciences (1997) 352: 987-996.
Interactions between plant nutrients, water and carbon dioxide as factors limiting crop yields.