Response surfaces of semidwarf wheat for seeding rate, and levels and times of application of nitrogen fertiliser

Abstract

A three factor central composite second order design in incomplete blocks was used to quantify the responses of semidwarf 'Karamu' wheat established at five seeding rates (170-580 seeds/m 2 ), and fertilised at five rates of N at the onset of tillering (0-124 kg/hal and during spikelet growth (0-38 kg/ha). N applied at tillering raised grain yields by increasing spike populations and the mean number of spike lets per spike, but generally depressed mean grain dry weights and, at low rates, reduced grain content. Persistence of N in the soil after higher rates of application may have accounted for its linear responses in that it influenced more of the yield components. N fertiliser applied during spikelet growth tended to reduce spike populations, and its effects on other yield components depended on the level of N applied at early tillering. Thus it depressed spikelets per ~.pike and mean grain weight when no N was applied at tillering and increased the values of these components when high rates were applied. Applications of N at tillering generally increased grain N content and grain N yield but had little influence on grain yield. Seeding rate increments modified components of yield but had little effect on grain yield or grain N content. Spike populations increased linearly with seeding rate but mean numbers of spikelets per spike declined especially at lower levels of N nutrition. At low seeding rates N appeared to be limiting grain set whereas at higher seeding rates assimilates appeared to be limiting. Thus the effects of seeding rate and N fertilisers at tillering were related to their common effect on spike populations.

Effect of ear populations on wheat production in the Manawatu and Rangitikei

“…In this work the relationship between grain yield and its components was similar to that discussed by Scott et al (1975), Dougherty et al (1974Dougherty et al ( , 1978Dougherty et al ( , 1979, and Nourafza & Langer (1979). The most significant component of grain yield, up to an optimum population, which differed for the two soil types, was ear number at maturity.…”

Response surfaces of “Kopara” wheat for seeding rate, and levels and times of application of nitrogen fertiliser

“…Kopara produced about one more spikelet per spike than the semidwarf (Dougherty et al 1978), probably because Kopara reached the 2'0…”

“…Similar treatments were incorporated in a factorial arranged in randomised blocks to compare the efficiencies of these designs in agronomic experimentation. Results obtained for the factorial design have already been published (Scott 1978), and information we obtained on Karamu and on relative efficiencies has been summarised (Dougherty et al 1978). In this paper we present results for Kopara and compare its responses to that of Karamu.…”

Effects of three N strategies on tillering and yield of low shoot density winter wheat

“…Nitrogen generally improves yield by increasing ear density and number of grains per ear, i.e. the number of grains per m 2 , whereas grain weight only varies slightly (Dougherty, 1978;Darwinkel, 1983;Siddique, 1989;Gooding & Davies, 1997). Darwinkel (1983) found that the maximum effect on: (1) Tiller formation and spikelet initiation occurred when N was supplied at the beginning of tillering (GS21); (2) number of shoots with ears when N was given at the beginning of stem elongation (GS30); (3) number of fertile flowers per spikelet, grains per fertile spikelet and ultimately grains per ear when N was applied during stem elongation until flag leaf emergence (GS30-39); and (4) grain weight when N was given at ear emergence (GS47).…”