ChileanJAR

During the years 1983 and 1984 two factorial trials were made on wheat at Experimental Substation Hidango of Chilean, VI Region, with marine-mediterranean climate and 950 - 1,500 mm averagerainfall during crop season respectively. Factors were: early variety vs. semi-early; early seeding vs. normal and no fertilization vs. 150 kg ha^-1 of N. Available N (N_s) in the soil to a depth of 140 cm and total N in the crop (N_c) were periodically determined. The sum of both was named movable N (N_m). A remarkable reduction of N_m was observed in winter. A part of this reduction can be explained by the method of sampling, but a certain amount of biological inmovilization is probably involved. During springtime Nm raised to little higher levels than inicial N (inicial N_s plus fertilizer N) in the treatments with fertilizer N, and much higher than inicial N in those treatments without fertilizer N. This suplementary N was estimated to come from residual biomass. From the end of spring to harvest N_m got down again. At harvest time final N_m was higher than inicial N in the treatments without fertilizer N; In the treatments with fertilizer N, final N_m was equal or lower than inicial N. The fall of Nm from springtime to harvest was thought to be caused by volatilization from the crop. Biological efficiency (final N_c/inicial N) was always higher in the treatment without N fertilizer than the corresponding treatments with fertilizer N (average 0.85 vS. 0.58). Average efficiency of fertilizer N was 0.38.