ABSTRACT:Cover crops contribute to nutrient cycling and may improve soil chemical properties and, consequently, increase crop yield. The aim of this study was to evaluate cover crop residue decomposition and nutrient release, and the effects of these plants on soil chemical properties and on onion (Allium cepa L.) yield in a no-tillage system. The experiment was carried out in an Inceptisol in southern Brazil, where cover crops were sown in April 2012 and 2013. In July 2013, shoots of weeds (WD), black oats (BO), rye (RY), oilseed radish (RD), oilseed radish + black oats (RD + BO), and oilseed radish + rye (RD + RY) were cut at ground level and part of these material from each treatment was placed in litter bags. The litter bags were distributed on the soil surface and were collected at 0, 30, 45, 60, 75, and 90 days after distribution (DAD). The residues in the litter bags were dried, weighed, and ground, and then analyzed to quantify lignin, cellulose, non-structural biomass, total organic carbon (TOC), N, P, K, Ca, and Mg. In November 2012 and 2013, onion crops were harvested to quantify yield, and bulbs were classified according to diameter, and the number of rotted and flowering bulbs was determined. Soil in the 0.00-0.10 m layer was collected for chemical analysis before transplanting and after harvesting onion in December 2012 and 2013. The rye plant residues presented the highest half-life and they released less nutrients until 90 DAD. The great permanence of rye residue was considered a protection to soil surface, the opposite was observed with spontaneous vegetation. The cultivation and addition of dry residue of cover crops increased the onion yield at 2.5 Mg ha -1 .

IMatéria seca de plantas de cobertura, produção de cebola e atributos químicos do solo em sistema plantio direto agroecológico ABSTRACT The cultivation and deposition of waste from cover crops in no-tillage can affect soil chemical attributes and onion yield. The aim of this study was to evaluate the dry matter yield of plant species from winter cover crops, onion yield and chemical attributes of soil in agroecological no-tillage system. The experiment was carried out at EPAGRI Experimental Station in Ituporanga (SC) under Humic

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RESUMOMesmo com expectativas de expansão das áreas agrícolas brasileiras sob sistema de plantio direto (SPD), são poucos os trabalhos sobre o controle de plantas invasoras sem o uso de herbicidas, principalmente na produção de hortaliças, como a cebola. Para tanto, culturas utilizadas para cobertura do solo se mostram eficientes no controle do desenvolvimento de plantas invasoras através da inibição física e/ou alelopática. O objetivo do presente trabalho foi avaliar diferentes espécies de cobertura do solo, em sistemas em monocultivo ou consorciados, no controle de plantas invasoras e a sua interferência na produção de cebola sob SPD em transição agroecológica. O experimento foi instalado na Estação Experimental da Epagri em Ituporanga (SC), em um Cambissolo Húmico. Os tratamentos foram: T1: testemunha (vegetação invasora); T2: aveia preta (Avena strigosa); T3: centeio (Secale cereale); T4: nabo-forrageiro (Raphanus sativus); T5: consócio de nabo-forrageiro e centeio; T6: consórcio de nabo-forrageiro e aveia preta. Os tratamentos nabo-forrageiro e nabo-forrageiro + centeio aos 60 dias após a semeadura (DAS) e centeio e nabo-forrageiro + centeio aos 120 DAS propiciaram a maior produção de matéria seca de plantas de cobertura, enquanto a menor produção de matéria seca de plantas invasoras foi obtida nos tratamentos nabo-forrageiro + centeio, seguido de nabo-forrageiro no início do ciclo da cebola. A maior produção de bulbos de cebola da classe 3 (50mm≤ᶲ˂70mm) e total, em relação à testemunha, também foi obtida nestes dois tratamentos.Palavras-chave: adubação verde, manejo ecológico do solo, Allium cepa. ABSTRACTEven with expectations of expanding Brazilian agricultural areas under no-tillage system, there are few studies that focus this system of yield without application of herbicide to weeds control are not very significant, mostly for vegetables production, like onions. In this sense, the use of cover crops presents efficient in weeds development control to inhibit by a physical barrier and/or its allelopathic effects. This study aimed to evaluate cover crops influences in the weeds control and onions yield under agroecological transition no-tillage system. The experimental area is located in Experimental Station of Epagri, Ituporanga (SC), in a Humic Haplumbrept soil. Treatments were: T1: control -weed community; T2: oat (Avena strigosa); T3: rye (Secale cereale); T4: white radish (Raphanus sativus); T5: white radish intercropped with rye; T6: white radish intercropped with oat. The treatments Raphanus sativus + Secale cereale at 60 days after sowing and Raphanus sativus + Secale cereale at 120 days after sowing propitiated highest dry matter yield of cover crops, while the lowest dry matter yield of weeds was obtained in treatments Raphanus sativus + Secale cereale, followed by Raphanus sativus in the early season onion. The highest yield of onion bulbs of the class 3 (50mm≤ᶲ˂70mm) and total, compared to the control, was also obtained in these two treatments.

JJ. Nitrous oxide emissions in no-tillage onion (Allium cepa L.) crops are increased by oilseed radish cover crop and poultry manure application. Rev Bras Cienc Solo. 2019;43:e0180116.