Nitrogen Recycling by Nonleguminous Winter Cover Crops to Reduce Leaching in Potato Rotations

Abstract

if (i) sufficient heat units are available to promote cover crop growth, root exploration, and N uptake during fall and winter; and (ii) mineralization rates of the green-Overwinter N leaching increases the potential for NO 3 contamination of ground water under irrigated desert soils. Our objectives were manured residues in the spring coincide with the timing to (i) identify winter cover crops for recovering N and (ii) determine of cash crop N demand. Effective fall-sown cover crops the N availability following green manure cover crops relative to N should exhibit rapid germination, aggressive and extenuptake by a succeeding potato (Solanum tuberosum L.) crop. A 2-yr sive rooting systems (Sainju et al., 1998), good winter field study was conducted on commercial fields on Quincy loamy hardiness, and early spring regrowth. Cereal and brassand (mixed mesic Xeric Torripsamments). Cover crops were seeded sica crops display these characteristics and are well following sweet corn (Zea mays L.) as fall-incorporated sudangrass suited for winter cover cropping (Wagger and Mengel, (Sorghum bicolor L., 'Sordan'); fall-and spring-incorporated white 1988; Brinsfield and Staver, 1991). These cover crops mustard (Brassica hirta Moench, 'Martegena'); and spring-incorpocan accumulate up to 150 kg N ha Ϫ1 (Hoyt and Mikrated wheat (Triticum aestivum L., 'Stevens'), rapeseed (B. napus kelsen, 1991; Shennan, 1992; Ditsch et al., 1993), with L., 'Jupiter'), and rye (Secale cereale L.). Potato ('Russet Burbank') was planted 3 to 5 wk after spring incorporation of green manures. rooting systems reaching depths of between 80 and 150All cover crops except sudangrass accumulated 112 to 142 kg N ha Ϫ1 cm Sarrantonio, 1992). when planted in August at Plymouth, WA, but N uptake was de-Following green manure incorporation, cover crops creased by Ͼ50% when planted in September at Quincy, WA. Overmay supply 20 to 55% of the recovered N to the subsewintering cover crops lowered soil mineral N at 0 to 180 cm by 155 quent crop (Sims and Slinkard, 1991; Malpassi et al., kg N ha Ϫ1 compared with bare fallow at Plymouth. Fall-incorporated 2000). Subsequent fertilizer requirements can be greatly mustard released greater inorganic N over the winter compared with reduced or eliminated (Griffin et al., 2000) if N release is spring incorporation. Soil NH 4 and NO 3 increased following overwinsynchronized with N demand of the succeeding summer tering cover crops by potato planting, providing timely increases in crop (Stute and Posner, 1995). Poor synchronization N availability to the potato crop. Winter cover crops can improve N or delays in N mineralization of cover crop residue, cycling and reduce the amount of N below the root zone in potatobased rotations.

Nitrogen cycling, profit margins and sweet corn yield under fall cover crop systems

“…At Ridgetown, OSR and OSR&Rye had higher biomass and plant N content compared with that observed by Vyn et al (2000) and Weinert et al (2002). The high plant N content in OSR and OSR&Rye treatments at Ridgetown was likely due to the fact that plants reached physiological maturity and set viable seed.…”

“…Soil mineral N was likely higher in OSR&Rye than oat and rye treatment due to rapid decomposition of OSR leaf and root tissues. After a killing frost, Weinert et al (2002) also found that rye had lower soil mineral N levels than a no-cover and a Brassica cover crop.…”

“…Sci. Downloaded from pubs.aic.ca by UNIV GUELPH on 03/09/12 and Weinert et al (2002) observed rye and Brassica cover crop N content of 114 to 140 kg N ha (1 . Likewise, when greater than 3000 kg ha (1 of shoot biomass was produced, cover crops have been found to accumulate over 100 kg N ha (1 (Weinert et al 2002).…”

“…Nitrogen is most prone to loss when mineral N is present in the soil and/or when crop residues mineralize during long periods of fallow (Weinert et al 2002). Several vegetable crops, such as fresh pea, can leave fields without a crop for up to 9 mo of the year, resulting in a long time period for N losses to occur.…”

“…Based on a cover crop N content of 100 kg N ha (1 (Weinert et al 2002), sweet corn acreage in Canada and N fertilizer cost of $1 kg (1 , this would amount to a $0.6 to $1.65 million reduction in N fertilizer input costs for growers. However, in order to reduce N fertilizers without compromising yield, cover crop N mineralization should be in synchrony with N demand of the following crop (Vyn et al 2000;Weinert et al 2002).…”