Cycling of nutrients and silicon in pigeonpea and pearl millet monoculture and intercropping

Abstract

SUMMARYIn a no-tillage system, cover crops must be used that combine shoot dry matter production and nutrient recycling. The aim of this study was to evaluate shoot dry matter production, decomposition rate and macronutrient and silicon release from pigeonpea and pearl millet in monoculture and intercropping systems. A randomized block design was used with a 3 x 6 factorial arrangement, with four replications. The first factor consisted of three cover crops (pigeonpea, pearl millet and intercropping of these cover crops) and the second consisted of six sampling times [0, 18, 32, 46, 74 and 91 days after desiccation (DAD)]. Pearl millet produced greater amounts of shoot dry matter and content of N, P, K, Ca, Mg, S, C and Si and had a higher decomposition rate and macronutrient and Si release than the other cover crops. The rates of decomposition and daily nutrient release from shoot dry matter were highest in the first period of evaluation (0-18 DAD). Over time, the C/N, C/P and C/S ratios increased, while C/Si and the decomposition rate decreased. Potassium was the nutrient most quickly released to the soil, especially from pearl millet residue. Silicon had the lowest release rate, with 62, 82 and 74 % of the total content in the shoot dry matter remaining in the last evaluation of pearl millet, pigeonpea and in the intercrop system, respectively. The shoot dry matter from the intercrop system had a different decomposition rate than that from the pearl millet monoculture and pigeonpea. Plants with greater shoot dry matter production and lower C/Si ratio are more effective in a no-tillage system for providing a more complete and persistent soil cover.Index terms: Cajanus cajan, Pennisetum glaucum, intercropping, nutrient release. RESUMO: CICLAGEM DE NUTRIENTES E SILÍCIO PELO GUANDU-ANÃO E MILHETO CULTIVADOS SOLTEIROS E CONSORCIADOSAs características mais importantes na escolha de plantas de cobertura para o sistema plantio direto são a quantidade e a durabilidade da fitomassa produzida, bem como a capacidade de reciclar nutrientes. Este estudo objetivou avaliar a produção de fitomassa, taxa de decomposição e ciclagem de macronutrientes e silício pelo guandu-anão e milheto, em cultivo solteiro e consorciado. O delineamento experimental foi em blocos casualizados, com quatro repetições, em esquema fatorial 3 x 6, constituído por três tipos de cobertura vegetal (guandu-anão, milheto e o consórcio dessas espécies) e seis épocas de coleta [0, 18, 32, 46, 74 e 91 dias, após a dessecação (DAD)]. O milheto produziu maior quantidade de fitomassa, acumulou mais N, P, K, Ca, Mg, S, C e Si e teve maior taxa de decomposição e de liberação de macronutrientes e Si que as demais coberturas vegetais. As maiores taxas de decomposição e liberação diária de nutrientes das fitomassas ocorreram no primeiro período de avaliação (0 a 18 DAD). Com o passar do tempo ocorreu aumento das relações C/N, C/P e C/S e redução na relação C/Si e na taxa de decomposição da fitomassa. O K foi o nutriente mais rapidamente disponibilizado ao solo, e...

Characterization of cover crops by NMR spectroscopy: impacts on soil carbon, nitrogen and phosphorus under tillage regimes

“…Increases in the C/N ratio were observed under Mucuna pruriens during the dry season and at 0-5 cm layer of soil (Table 5) owing to the higher concentration of recalcitrant aromatic compounds in the plant tissue Averages followed by different lower-case letters along each column and upper-case letters in each row differed according to the Tukey test at 5% probability level Table 3 of this specie. Although Cajanus cajan has high concentration of more stable compounds (aromatic compounds and alkyls) it did not promote a higher C/N ratio in the soil, possibly due to its lower production of biomass (CARVALHO et al, 2008;CRUSCIOL et al, 2013) and maize straw in the plots with this cover crop.…”

“…Results from Crusciol et al (2013) and Balota;Chaves (2011) show that the C/N ratio of Mucuna pruriens (16.4) is lower than that from Cajanus cajan (32). However, the chemical composition of these leguminous crops is similar, particularly in the aromatic carbon compound region, confirming the relationship between the composition of carbon compounds and the decomposition of plant material (RANDAL et al, 1997).…”

“…The values of the C/N and C/ P ratios in plants expresses its durability as cover crops in the no-tillage (CRUSCIOL et al, 2013;SORATTO et al, 2012). The slower decomposition of Cajanus cajan and Mucuna pruriens residues, mainly due to lower levels of polysaccharides compared to more stable aromatic A.…”

“…Considering 31,5 million hectares under no-tillage in Brazil in (FEBRAPDP, 2012 and that an increase of 8 million hectares by 2020 has been planned by the Brazilian government as one of the main approaches for greenhouse gas mitigation (BRASIL, 2012), more information is needed on the chemical composition of decomposing plant residues and their influence on the stocks of carbon and other nutrients. Moreover, one of the basic requirements for the implementation and maintenance of no-tillage in Brazil is the adequate production of plant residues in order to keep the soil surface continuously covered and to recycle nutrients and gradually make them available to successive crops (CRUSCIOL et al, 2013).…”

Nitrogen fertilization on palisadegrass: phytomass decomposition and nutrients release

“…If compared with other species commonly used as cover crops, such as pearl millet, pigeonpea (Crusciol et al 2013) and sun hemp (Costa et al 2012), palisadegrass exhibits significant nutrient cycling potential, especially S. Palisadegrass has a low decomposition and nutrient release rate, particularly for N, Ca, Mg and Si. Therefore, in regions with dry winters and hot and rainy summers, as well as low water availability, this species is a promising alternative for the continuity and sustainability of a no-tillage system, since it provides greater soil protection and a gradual release of nutrients to the subsequent crop.…”