Bioenergetic and energy constraints in increasing cereal productivity

Abstract

The grain yield potential of cereal crops such as wheat, rice, barley, oats and sorghum has increased by genetic improvement in the harvest index (grain yield/biological yield). Such alterations in the harvest index were analysed from the point of view of intrinsic energy and nitrogen, phosphorus and potassium requirements. A higher harvest index, without any reduction in biological yield, increases the harvest of: (a) energy (MJ) in the above ground parts of the crop and (b) nitrogen and phosphorus in the grain. In addition, it enhances the fertiliser requirement of the crop. From bioenergetic considerations, higher grain yields, obtained by improving the harvest index, represent a path which demands least increments in photosynthate and nutrient inputs. The other alternatives available for increasing cereal productivity, once the upper limits of the harvest index are reached by breeding, have higher costs in terms of photosynthate and fertiliser requirements (energy inputs). There seems to be no other immediate plant breeding alternative to increase productivity without additional energy (fertiliser) inputs.