Effects of plant density and nitroǵen fertilizer on growth and yield of short varieties of wheat derived from Norin 10

Abstract

SUMMARYThe short varieties of spring wheat, Lerma Rojo 64 (R) and Mexico 120 (M), derived from Norin 10, had similar yields of grain to the taller European variety, Kloka (K), when the nitrogen applied ranged from 50 to 200 kg/ha. All varieties had their maximum yields, of about 500 g/m2 of grain, with 125 kg/ha of N. Yields of R and M were unaffected by change in plant population from 75 (M) or 105 (R) to 298 plants/m2. There were 213 plants of K per m2. When compared at similar plant populations, all varieties had a similar number of ears of similar weights. Ears of K had many small grains borne on many spikelets. Those of R had fewest spikelets and most grains per spikelet. With 213 plants/m2 about 60% of shoots of K and 70% of those of R and M survived to produce ears.The short variety of winter wheat Gaines (G), derived from Norin 10, had a similar yield of grain to the taller European variety Cappelle‐Desprez (C), when nitrogen ranged from 75 to 300 kg/ha and there were 240 plants/m2. The largest grain yields of both varieties, about 670 g/m2, were obtained with 150 kg/ha of N. Increasing the plant population of G to 400 plants/m2 decreased grain yield by 10%. G had more ears than C and the ears weighed less because the grains were smaller. The numbers of grains per ear were similar: ears of G had fewer spikelets than C, each bearing more grains. G always had more shoots than C and about 70% of the shoots produced by each variety survived to form ears.The dry weight per m2 of stem plus leaves of the short varieties was less than of the tall ones at flowering and at maturity. Hence harvest index (ratio of grain yield to total dry weight), and the proportion of total dry weight in the ears at flowering, were greater for the short than for the tall varieties.Grain leaf ratio, the apparent efficiency of the leaf area present after flowering in producing grain, estimated as grain dry weight divided by leaf area duration after flowering, was greatest for M and least for K in the spring experiment. No similar difference occurred between the winter varieties. When leaf area of either spring or winter varieties was increased by nitrogen fertilizer or denser sowing, grain yield did not increase proportionately and so grain leaf ratio decreased.