Levels of water‐soluble carbohydrate in the pre‐anthesis ear of wheat, and grain set per spikelet

Low levels of water‐soluble carbohydrates in wheat ears before emergence were associated with poor grain set per spikelet when seeding rates were approximately twice conventional ones. Grain set and grain filling in ‘Arawa’ were better than in ‘Aotea’, and ‘Arawa’ also had higher levels of water‐soluble carbohydrate in the pre‐anthesis ears. There was no obvious relationship between nitrogen fertilisation and water‐soluble carbohydrate content of ears near emergence. Irrigation tended to lower levels of water‐soluble carbohydrate in pre‐anthesis ears of ‘Aotea’ and ‘Arawa’ and reduce grain set. Reduction in grain set through irrigation was greater in wheat to which nitrogen fertiliser was applied. ‘Karamu’, a semidwarf wheat, set more grains in mid‐ear spikelets when nitrogen was applied, whereas the New Zealand cultivars ‘Aotea’ and ‘Arawa’ did not.