Nitrogen Availability from Surface‐Applied and Soil‐Incorporated Crop Residues

Abstract

Management systems which maintain crop residues on the soil surface have prompted a need for more detailed information regarding crop residue N availability. Such information is needed from both agronomic and environmental standpoints. Our study examined the placement effects of 15N tagged alfalfa (Medicago sativa L.), sorghum [Sorghum bicolor (L.) Moench], and wheat (Triticum aestivum L.) residues on crop residue N availability in association with eight Oklahoma surface soils representing five soil orders. The experiment was conducted under aerobic laboratory conditions, and involved 0.25‐mm crop residue materials and 2‐mm soil particles. Crop residue N availability was determined on the basis of N mineralized during short‐term (14 d) and long‐term (168 d) incubation. Mean amounts of crop residue N mineralized ranged from <18 kg N ha−1 for sorghum and wheat (<28% of residue N) to 55 kg N ha−1 for alfalfa (35% of residue N). Surface placement of crop residue reduced residue N availability compared to soil incorporation, but the differences were only equivalent to 1 to 7 kg N ha−1. Relative to residue type, the influence of soil type on crop residue N mineralization was secondary. Overall, differences in crop residue N availability associated with residue placement should have minor agronomic and environmental impact.

Utilização de nitrogênio de adubos verde e mineral pelo milho

“…Fatores externos, como condições ambientais (Janzen & Radder, 1989;Stanford & Smith, 1972), tipo de solo (Ladd et al, 1981;Janns-Hammermeister et al, 1994) e forma de manejo (Wilson & Hargrove, 1986;Janzen & Radder, 1989), e inerentes aos adubos verdes (Palm & Sanchez, 1991;Smith & Sharpley, 1993), exercem grande influência sobre tais processos, devendo ser compreendidos e, na medida do possível, controlados para que otimizem os efeitos da adubação verde.…”

In‐Season Nitrogen Effects on Organic Hard Red Winter Wheat Yield and Quality

“…For instance, Salomonsson et al (1994) found that while bone meal applied to spring wheat just before stem extension increased grain protein to the same level as topdressed urea, slurry manure N was less available and had to be applied at planting to achieve a comparable increase in protein. The slower N availability from organic N sources may be exacerbated by the lack of soil incorporation with topdressing that could reduce N mineralization (Smith and Sharpley, 1993) or increase N volatilization losses (Cabrera et al, 1993). If true, incorporating organic N topdress sources with in‐season cultivation as is performed for weed management (Kolb and Gallandt, 2012) may increase N availability and subsequent plant uptake.…”

Placement of Preplant Liquid Nitrogen and Phosphorus Fertilizer and Nitrogen Rate Affects No‐Till Wheat Following Different Summer Crops

“…Leaving previous crop residues near the soil surface, such as in NT, affects fertilizer N management for winter wheat (Westfall et al, 1996). Decomposing crop residues with wide C/N ratios can immobilize significant amounts of surface‐applied fertilizer N and/or slow mineralization of soil N (Rice and Smith, 1984; Knowles et al, 1993; Smith and Sharpley, 1993). Several researchers have reported lower wheat yields and a greater fertilizer N requirement for wheat planted after a high‐residue crop such as grain sorghum, compared with wheat planted after soybean, and have attributed much of those results to greater immobilization of N after grain sorghum (Hargrove et al, 1983; Sanford and Hairston, 1984; Staggenborg et al, 2003).…”