Grain yield, nitrogen uptake and use efficiency components of South African irrigation wheat cultivars under different nitrogen management strategies

The effect of different N management strategies on the grain yield, N uptake and use efficiency components of five commercial wheat cultivars were investigated for two consecutive years at Riet River and Loskop irrigation schemes. The cultivars ranged ingrowth period to initial flowering, from 95, 102, 106, 108 and 109 days for SST 822, Steenbras, SST 876, Olifants and Baviaans. Management strategies consisted of zero (NO) and recommended Napplication split-applied at different growth stages (N1 = 100% at planting; N2 = 54% at planting, 23% at stem elongation and 23% at flag leaf; N3 = 38% at planting, 44% at stem elongation and 18% at flag leaf; N4 = 100% at stem elongation in the first year, and 37% at planting and 63% at stem elongation in the second year). The lowest grain yield and N uptake resulted for N0, followed by N4 and then either N1, N2 and N3. The longer-growing Baviaans, Olifants and SST 876 (more than 106 days to flowering) responded more to N fertilization than the shorter growing Steenbras and SST 822 (less than 102 days to flowering). This also applied to grain yield, N uptake and N harvest index. The cultivars SST 822 and Steenbras had the lowest and SST 876 the highest N physiological efficiency (NPE). Application of N had limited effect on the agronomic (NAE) and recoveryefficiency (NRE) of the element. The results of this study showed that several factors must be considered in the selection of N efficient wheat cultivars.