Increasing Wheat Grain Size and Weight

Wheat grain size is strongly influenced by plant nutrition particularly during the important grain filling period. Nitrogen, phosphate, potassium, magnesium and zinc are particularly important.

Wheat yield targets and components to benchmark

Wheat grain size is determined by the plants genetics i.e. variety, and the length of the grain filling period. As soon as pollination has occurred the embryo and endosperm begin to develop with the plant redirecting photosynthates and also previously stored starch and protein (in leaves and stems) to these developing grains. The longer this period of grain fill is, the larger wheat grain size is likely to be.

Nitrogen has a large effect on grain size and weight

Nitrogen management will have the most impact on final wheat grain size and weight. Applications made early will ensure a canopy that is large, containing high levels of stem carbohydrate that is translocated to the developing grain during maturation.

Effect of high or low nitrogen in three wheat development periods

This is particularly important in drought areas where 60% of the grain yield could come from this store. It is important to monitor plant nitrogen levels ensuring the canopy does not senesce early and curtail the grain filling period.

Phosphate improves grain size

Phosphate has a major role in the supply of energy for plant processes. Redistribution of stored carbohydrate requires energy making phosphate nutrition important in achieving good wheat grain size.

Both solid fertiliser phosphate and foliar phosphate can be used to improve final grain size.

Potassium extends grain filling period

Potassium aids movement of nutrients around the plant as it regulates the transpiration flows as the wheat plant redistributes minerals to the ear potassium levels need to be maintained.

Effect of potassium supply on the length of grain filling period in wheat

Effect of potassium supply on 1000 grain weight of wheat

Potassium will also help avoid early senescence often brought on by drought during grain fill. Potassium deficient plants are poor at regulating transpiration through the leaf leading to heat stress and wilting. Adequate potassium supplies will extend the grain filling period leading to improvements in wheat grain weight.

Manganese and zinc influence grain size and weight

Both manganese and zinc with their roles in nitrogen metabolism by the plant will improve wheat grain weight.

Effect of manganese and zinc on the 1000 grain weight of wheat

 

Other factors influencing wheat grain size

Besides nutrient management, the grain size can be influenced by water management (irrigation to avoid drought stress), as well as disease management – use fungicides and nutrients to maintain green leaf area and reduce disease incidence improving plant health.

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