Time of Desiccation Effects on Plant Composition and Subsequent Nitrogen Release from Several Winter Annual Cover Crops

Abstract

Efficient utilization of N contained in cover crop residues by the subsequent summer crop requires an understanding of temporal patterns of N release as related to specific management strategies. The objective of this research was to determine, under field conditions, changes in plant composition and subsequent patterns of N release resulting from two desiccation dates approximately 2 wk apart (early and late) for rye (Secale cereale L.), crimson clover (Trifolium incarnatum L.), and hairy vetch (Vicia villosa Roth) cover crops. Averaged over 2 yr the late desiccation treatment resulted in increases in cover crop dry matter of 39, 41, and 61% for rye, crimson clover, and hairy vetch, respectively. Corresponding increases in total N content of the respective cover crops were 14, 23, and 41%. Significant differences in cellulose, hemicellulose, and lignin contents were found among cover crop residues between desiccation times. Nitrogen release from decomposing cover crop residues was monitored using nylon mesh (53 µm) bags. In general, the order of N release was hairy vetch > crimson clover > rye. Cover crops desiccated early decomposed faster, however, the relative magnitude of these N release patterns differed sharply between years. The percentage of initial residue N remaining after 16 wk for the early desiccation date in 1984 was 53, 14, and 13% for rye, crimson clover, and hairy vetch, respectively, compared with corresponding values of 59, 42, and 35% in 1985, which was characterized by a relatively dry growing season. Estimates of N released from each cover crop indicated that the potentially larger available N pool resulting from a delay in desiccation was offset by the slower rate of N release, especially for rye and crimson clover.

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

“…In the following growing season, the lack of increase in soil mineral N in nonleguminous cover crop treatments compared with nocover was consistent with other research (Wagger 1989;Vyn et al 1999). It is possible that net N mineralization of cover crops did not match up with sweet corn N demand.…”

“…Vyn et al (2000) also found no difference in cover crop N content among rye, oat and OSR sampled in late fall in a 3-yr study in southern Ontario. Similar to Bothwell in December and Ridgetown in October, Wagger (1989) …”

“…It is possible that net N mineralization of cover crops did not match up with sweet corn N demand. For instance, although highly dependent on cover crop plant chemical composition (Wagger 1989;Janssen 1996) and environmental conditions (Miller et al 1994), mineralization of cover crops can be rapid, within 5 d of incorporation (Jackson et al 1993). At both sites cover crops were incorporated a few days prior to sweet corn planting.…”

Dinâmica de decomposição e liberação de nutrientes de genótipos de guandu sob cultivo em aléias

“…Isso equivaleria à liberação de aproximadamente 80 kg ha -1 de N, se considerar a média de 208,1 kg ha -1 na fitomassa produzida (Figura 1). Esses resultados confirmam os obtidos, em condições de campo, por Wagger (1989), Amado et al (2000) e Aita et al (2001). Aita & Giacomini (2003), ao avaliar a dinâmica da decomposição e liberação de N de resíduos culturais, observaram que enquanto em ervilhaca menos de 60% do N permaneceu nos resíduos culturais, nos primeiros 15 dias, no nabo e na aveia esse valor foi superior a 90%.…”

“…Mesmo no sistema de cultivo em aléias, em que os resí-duos culturais permanecem na superfície do solo depois da poda, a liberação de nutrientes, na fase inicial de decomposição, pode superar a quantidade de nutrientes acumulados pelas culturas comerciais. Nas duas últimas décadas, foram realizados diversos trabalhos com plantas de cobertura de solo no outono/inverno, tanto no Brasil quanto em outros países, procurando-se caracterizar a decomposição e a liberação de N de seus resíduos culturais (Wagger, 1989;Ranells & Wagger, 1992;Da Ros, 1993;Aita & Giacomini, 2003). Esses estudos evidenciaram que as leguminosas, especialmente quando usadas como culturas solteiras, foram rapidamente decompostas depois do seu manejo, mesmo em sistemas de plantio direto, o que resultou num assincronismo entre a liberação de nutrientes dos seus resíduos culturais e a demanda de nutrientes pela cultura em sucessão.…”