Winter Cover Cropping Influence on Nitrogen in Soil

Abstract

Winter cover crops may affect the short‐ and long‐term N availability in soil depending on the quantity, quality, and degradation rate of biomass returned to the soil. We examined the effects of several cover crops on soil inorganic and organic N levels in a winter cover crop‐silage corn (Zea mays L.) double‐cropping system that was initiated in 1987. High biomass N concentrations (BMN) in the above‐ and belowground biomass of the leguminous cover crops corresponded to high levels of inorganic N and water‐soluble N, but low levels of water‐soluble C and carbohydrate compared with the nonleguminous cover crops. The BMN above which there was net N mineralization 4 wk after residue incorporation was 17.9 g N kg−1. The organic N from the aboveground biomass degraded rapidly. The first‐order rate constants for the degradation of organic N and C in the cover crops were significantly correlated. This, coupled with a significant correlation between the soil organic N (SON) levels and cumulative biomass C added, indicated the importance of biomass C inputs in organic N retention in the soil. The cover crops had variable short‐ and long‐term effects on soil N availability. Whereas rye (Secale cereale L. cv. Tetra Petkus) and annual ryegrass (Lolium multiflorum Lam. cv. Billion) were ineffective in increasing soil inorganic N levels, they were more effective than hairy vetch (Vicia villosa Roth subsp. villosa), Austrian winter pea (Lathryrus hirsutus L.), and canola (Brassica napus L. cv. Santana) in increasing SON accumulation because of a higher biomass potential and a larger input of biomass C.

Cover crops and nitrogen fertilization effects on soil carbon and nitrogen and tomato yield

“…Nitrogen concentration in the cover crop and weed biomass samples and tomato leaves, steams, and fruits were determined by the H 2 SO 4 -H 2 O 2 method described by Kuo et al (1997b). Carbon concentration in the cover crop and weed samples was determined by the Walkley-Black method (Nelson and Sommers 1996), assuming that all plant C was oxidized during digestion (Kuo et al 1997a).…”

“…4 and 5) may have resulted from the decreasing availability of organic N from their residues as they are decomposed in the soil. Several researchers (Wilson and Hargrove 1986;Stute and Posner 1995;Kuo et al 1997b) found that organic N from cover crop residue decomposed rapidly in the soil during the corn growing season in the summer, with a half-life ranging from 2 to 8 wk for hairy vetch, crimson clover, and rye. Franzluebbers et al (1995b) observed that PNM decreased from planting to flowering during the sorghum and soybean growing seasons in the summer with conventional tillage.…”

“…Winter cover crops use residual NO 3 that may leach into groundwater from the soil after crop harvesting (Sainju et al 1998), sequester atmospheric CO 2 to reduce global warming (Lal 1998), and depending on the species, can reduce the amount of N fertilization (Hargrove 1986;Kuo et al, 1997b). Although studies on long-term effects of winter cover crops on soil organic C and N are available (Hargrove 1986;Kuo et al 1997a,b), their short-term effects on available C and N, which influence microbial dynamics and nutrient availability, are not well known.…”

Cover Crop Management in a Chardonnay/99 Richter Vineyard in the Coastal Region, South Africa. 3. Effect of Different Cover Crops and Cover Crop Management Practices on Organic Matter and Macro-nutrient Content of a Medium-textured Soil

“…Over a period of six years, a 150 mm-thick straw mulch resulted in a 17% increase in organic matter in the 0 to 200 mm soil layer of a Hudson silty clay loam with textural proportions of 7% sand, 71% silt and 22% clay and an initial organic matter content of 0.53% (Merwin and Stiles, 1994). Continuous winter cropping with Secale cereale L. v. Tetra Petkus ('Tetra Petkus' rye) resulted in a small increase in soil organic carbon (5 to 10 mg/kg), compared to the control treatment in which no cover crop was 11 Victoria Street,Stellenbosch 7600,Republic of South AfricaEffect of cover crop management on organic matter and macro-nutrients sown (Kuo et al, 1997). The organic matter content in the 0 to 100 mm soil layer of a sandy loam soil was increased from 0.54% to 0.95% over a period of four years with Medicago truncatula Gaertn.…”

Underseeded clover as a nitrogen source for spring wheat on a Gleysol

“…Furthermore, conflicting evidence exists on the effects of multiple cropping systems including a legume component on N loss reduction (Izaurralde et al 1995;Owens et al 1995;Weed and Kanwar 1996;Høgh-Jensen and Schjoerring 1997;Kuo et al 1997). While legume cover crop can reduce NO 3 -leaching by taking up soil mineral N (Francis et al 1998), the mineralisation of N from legume residues can increase the soluble mineral soil N pool for subsequent transfer if it is released at a time that is not synchronised with plant uptake (Campbell et al 1994).…”