EFFECTS OF FERTILIZER-NITROGEN AND WATER SUPPLY ON DISTRIBUTION OF DRY MATTER AND NITROGEN BETWEEN THE DIFFERENT PARTS OF WHEAT

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Abstract
Wheat in pots and in the field was subjected to different watering regimes and fertilizer-N, either as ammonium-N with a nitrification inhibitor or as nitrate-N, was applied at sowing or during growth. More weight of leaves and stems was produced during early growth with ammonium-N than with nitrate-N, but the two forms gave similar yields of grain. The grain:straw ratio with ammonium-N was smaller than with nitrate-N, and more N was retained in the straw. Both forms of N increased the weight per spike but not the number of spikes per unit area (tillering). Applied at the boot stage of growth, N increased dry matter much less than when applied at sowing, but increased the percent N in the grain. Divided dressings, half at sowing and half during growth, increased yield and N uptake by the same amount as applying all the N at sowing. Drought during spike formation or floret development led to smaller spikes and yields of grain, and also to a smaller grain:straw ratio; up to three-quarters of the extra N taken up from fertilizer-N remained in the straw.