Nitrogen Sources for Bean Seed Production¹

Abstract

Beans (Phase()las valgtais L.) often respond to N fertilization; however, N fertilization is not practiced for maximum seed production in southern Idaho. This suggests that the symbiotic relationship and/or soil N sources can provide most of the N needed by this legume. Our objective was to evaluate the relative contribution of the symbiotic-nonsymbiotic N sources by studying the effects of N fertilization on the symbiotic N. fixation and seed yields under field conditions. Experiments were conducted on silt loam soils belonging to the Portneuf series (Xerollic Calciortnids). An acetylene reduction (AR) method was used to determine the effect of N fertilization treatments on the relative seasonal N, (AR) fixation. The symbiotic N, fixation was also estimated by the equation, N. = N"" -(N, + N", N.) -aN., where N", is the accumulated N uptake measured near physiological maturity, N, and N,, are the amounts of soil NO,-N in the root zone before planting and near physiological maturity, N" is the N mineralized from soil organic N sources, and a is the recovery of the N fertilizer (N,) applied. Estimates of the N fertilizer recoveries were obtained from two experiments using 15N-depleted (NH4), SO,.The symbiotic N, relationship contributed up to 90 kg N/ha, which was 40 to 50% of the total N found in bean plants near physiological maturity. The amount of symbiotic N. fixed decreased as the available soil N or fertilizer N increased, and increased as the N required by the individual cultivars increased. The response to N fertilization depended upon the cultivar, as well as on the N_available from soil sources. Measured fertilizer N recoveries ranged from 7 to 33%. An average of 52% of the total N uptake near physiological maturity was taken up after the maximum symbiotic NAAR) rate occurred; while the seed contained an average of 60% of the total N uptake. A low N fertilization rate (< 50 kg Nilia) when the soil N, was low (<50 kg N/ha) ensured an early vi us plant growth but did not always increase seed yields. Higher N fertilization rates may be required on soils with lower amounts of mineralizable N.

Seeds enriched with phosphorus and molybdenum improve the contribution of biological nitrogen fixation to common bean as estimated by 15n isotope dilution

“…Even control plants showed a strong nodulation (Figure 1b), which reinforces the argument that the common bean is a promiscuous host regarding native soil rhizobia (Hungria et al, 2003). The addition of mineral N strongly reduced nodulation at both soil P levels (Figure 1b) since the Phaseolus-Rhizobium symbiosis is quite sensitive to soil nitrate (Westermann et al, 1981;Leidi & Rodríguez-Navarro, 2000). However, at the highest soil P level nodulation was less affected by the mineral N applied.…”

Root‐Zone Mineral Nitrogen Changes as Affected by Crop Sequence and Tillage

“…Nitrogen fixation would have been low because of the high soil NO3 levels found in the soil. Westermann et al (1981) measured only 10 kg ha-1 fixed by this cultivar when 223 kg N ha-' was present in the soil at the start of the season. Lower levels should result in less NO 3 leaching below the root zone under normal irrigation practices.…”

Resposta do Feijoeiro Comum à Inoculação com Rizóbio e Suplementação com Nitrogênio Mineral em Dois Biomas Brasileiros

“…A espécie é capaz de se associar simbioticamente a diversas bactérias do grupo dos rizóbios, formando nódulos nas raízes onde ocorre o processo de transformação do N 2 atmosférico em NH 3 assimilável pelas plantas, a fixação biológica de N (FBN). No feijoeiro comum, têm sido reportadas contribuições relevantes da FBN em condições de campo, como valores de N 2 fixado atingindo 90 kg ha -1 de N, correspondente a 50 % do N acumulado na maturação (Westermann et al, 1981), entre 40 e 125 kg ha -1 de N em diferentes cultivares (Rennie e Kemp, 1983), entre 21 e 44 kg ha -1 de N nos grãos de diversos genótipos (Pereira et al, 1989), e valores médios em sete diferentes países de 35 % do N derivado da atmosfera, com valores máximos de 70 % sob condições favoráveis (Hardarson et al, 1993). No entanto, a inoculação do feijoeiro com rizóbio pode não proporcionar a quantidade de N necessária para atingir altos níveis de produtividade em condições comerciais de cultivo.…”