Forage-corn production and N-fertilizer replacement values following 1 or 2 years of legumes

Abstract

The costs of N fertilizer and concern for sustainable agriculture have led to renewed interest in the use of legumes as a source of N for succeeding non-legume crops. In this regard, field experiments were conducted in 1987,1988 and 1989 on a Rivière-du-Loup sandy gravelly loam (Ferro-Humic Podzol) at St-Anselme and on a Chaloupe silty loam (Orthic Humic Gleysol) at Deschambault in eastern Quebec, Canada, to determine the effects of 1 or 2 years of faba bean (Vicia faba L.) Outlook and soybean (Glycine max [L.] Merr.) Maple Amber on subsequent forage-corn (Zea mays L.) Pioneer 3979 dry matter yields (DMY) and N uptake, and the N-fertilizer replacement values (NFRV) of the different crop sequences. Corn in monoculture or following a legume was fertilized with 0, 50, 100 or 150 kg N ha−1, and legumes received 20 kg N ha−1 as NH4NO3. In 1989, at both locations, the DMY and N uptake of forage corn in monoculture or following 2 consecutive years of soybean, or subsequent to soybean and faba bean grown 2 years previously, increased linearly with N application. After 2 consecutive years of faba bean, the DMY were not affected by increasing fertilization, but the N uptake generally increased proportionally to N application. The estimated NFRV (on a DMY basis) after 2 consecutive years of faba bean varied from 60 to 125 kg N ha−1 at St-Anselme, and from 100 to 110 kg N ha−1 at Deschambault for the ears and stover, respectively. The NFRV estimated for the same cropping sequence varied from 122 to 129 kg N ha−1 at St-Anselme and from 104 to 131 kg N ha−1 at Deschambault, for the stover and ears, respectively, on the basis of N uptake. For 2 consecutive years of soybean, it averaged 14 kg N ha−1 at St-Anselme and 33 kg N ha−1 at Deschambault, on the basis of the DMY; when based on the N uptake, the NFRV of 2 consecutive years of soybean varied from 14 to 21 kg N ha−1 at St-Anselme and from 0 to 15 kg N ha−1 at Deschambault for the stover and ears, respectively. The average NFRV (based on the DMY) for faba bean grown 2 years previously were 17 kg N ha−1 at St-Anselme but NFRV varied from 0 to 16 kg N ha−1 at Deschambault for stover and ears, respectively; on the basis of N uptake, the NFRV for the same crop sequence averaged 24 kg N ha−1 at St-Anselme, but varied from 0 to 15 kg N ha−1 at Deschambault for the stover and ears, respectively. Key words: Corn, faba bean, soybean, crop sequence, N fertilization