Ciclagem de nutrientes por plantas de cobertura na entressafra em um solo de cerrado

Abstract

Resumo -O objetivo deste trabalho foi avaliar o acúmulo e a liberação de nutrientes (N, P, K, Ca, Mg e S) de resíduos culturais de plantas de cobertura na entressafra, em condições de Cerrado. O experimento foi conduzido em um Latossolo Vermelho distroférrico com textura argilosa. As plantas de cobertura avaliadas foram: amaranto (Amaranthus cruentus L.), milheto (Pennisetum glaucum L.) e capim-pé-de-galinha (Eleusine coracana (L.) Gaertn.). O delineamento experimental utilizado foi o de blocos ao acaso, no esquema de parcelas subdivididas, com quatro repetições. Na fase de florescimento das espécies, foi avaliada a produção de matéria seca e o acúmulo de nutrientes. A fim de avaliar a liberação de nutrientes dos resíduos culturais, o material vegetal de cada espécie foi acondicionado em sacolas de náilon, as quais foram dispostas sobre o solo e seu conteúdo analisado em intervalos de 30 dias, até 240 dias após sua instalação. As maiores quantidades de nutrientes acumulados na fitomassa das plantas de cobertura foram observadas no milheto e no capim-pé-de-galinha. O potássio foi o nutriente acumulado em maior quantidade, chegando a atingir 416,9 kg ha -1 no milheto. As maiores taxas de liberação de nutrientes foram observadas nos resíduos culturais do amaranto.Termos para indexação: Amaranthus cruentus, Pennisetum glaucum, Eleusine coracana, dinâmica de decomposição, liberação de nutrientes, plantio direto. Nutrient cycling in off-season cover crops on a Brazilian savanna soilAbstract -The objective of this work was to evaluate the accumulation and the liberation of nutrients (N, P, K, Ca, Mg and S) of cultural residues by three species of cover crops, in off-season. Tested cover crops were amaranthus (Amaranthus cruentus L.), pearl millet (Pennisetum glaucum L.) and finger millet (Eleusine coracana (L.) Gaertn.). The experiment was carried out in a Typic Haplorthox clay texture soil. A randomized block desing in a split-plot array in time, with four replications, was used. At the flowering of the species, the production of dry matter and the accumulation of nutrients were evaluated. Proportional samples of dry matter of each cover crop species were placed in litter bags, which were distributed on the field plots surface, collected and weighed every 30 days, until 240 days after installation of the bags. The largest amounts of accumulated nutrients in the dry matter of the cover crops were observed with the pearl millet and the finger millet. The potassium was the nutrient accumulated in larger amount, reaching 416.9 kg ha -1 , in pearl millet. The largest rates of nutrient liberation were observed in the cultural residues of the amaranthus.Index terms: Amaranthus cruentus, Pennisetum glaucum, Eleusine coracana, decomposition dynamics, nutrient release, no-till. IntroduçãoA utilização e a ocupação agrícola da Região do Cerrado vêm ocorrendo com necessidade de adoção de novas tecnologias fundamentadas em bases conservacionistas. No sistema plantio direto, o uso de plantas de cobertura é uma alternativa para aumen...

Nitrogen washing from C3 and C4 cover grasses residues by rain

“…Results for black oat and triticale differed, i.e., the highest N dose (200 mg dm -3 ) for triticale and the calculated dose of 140 mg dm -3 of N for black oat increased N content and decreased C/N ratios of the straw (Figures 2 and 5). In an experiment using litter bags, N release from Amaranthus cruentus (C 3 ) was faster than than from Pennisetum glaucum and Eleusine coracana (C 4 ), which confirms our results (Boer et al, 2007). Therefore, in systems where these C 3 grasses are grown, at least part of the fertilizer N to be applied to the cash crop could be applied to the cover crops, which would recycle the N to the soil faster than C 4 species.…”

“…Usually, plant residues can be classified in two groups; fast and slow decomposition types, i.e., residues with C/N ratios higher than 25 strongly immobilize N and have a low decomposition rate; and on the contrary, C/N ratios below 25 indicate high N mineralization rate and fast plant residue decomposition (Boer et al, 2007). Generally, the higher the N rate, the lower the C/N ratio observed in the plant residues, which decreased from 36 to 23, 35 to 19, 24 to 11 and 28 to 10 for millet, congo grass, triticale and black oat, respectively.…”

Sequências de culturas em sistema de semeadura direta: II - decomposição e liberação de nutrientes na entressafra

“…Diversas espécies vegetais podem ser utilizadas como culturas de entressafra (cultivadas no outono/ inverno) com o objetivo específico de proporcionar cobertura do solo e reciclagem de nutrientes (Boer et al, 2007;Torres et al, 2008;Pacheco et al, 2011). O cultivo de leguminosas tem demonstrado ser uma alternativa promissora na suplementação de N para as culturas em sucessão (Amado et al, 2003;Sisti et al, 2004), devido à capacidade de fixação do N 2 atmosférico e à estreita relação carbono:nitrogênio (C:N) de seus resíduos, o que leva a uma rápida decomposição , disponibilizando ao solo, aos microrganismos e às plantas em sucessão, além do N e do C acumulados (Mulvaney et al, 2010), todos os nutrientes contidos na biomassa.…”

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

“…The persistence of shoot dry matter (SDM) on the soil, the nutrient recycling capacity, the mobilization of leached or not very soluble elements and their release to the subsequent crop are important indicators of the quality of cover crops (Boer et al, 2007;Crusciol & Soratto, 2007;Carneiro et al, 2008;Crusciol et al, 2005;Leite et al, 2010). Thus, it is not easy to unite all the aforementioned qualities in a single species, which should also increase the diversification in crop rotations or intercropping, providing soil protection and nutrient recycling in the no-tillage planting system under different soil and climatic conditions.…”

“…In the grain-producing regions of Brazil, characterized by dry winters, the grass species pearl millet (Pennisetum glaucum (L.) R. Brown) is the most commonly used cover species (Boer et al, 2007). This crop is characterized by high SDM production and persistence on the soil after desiccation (Silva et al, 2010) and high soil nutrient extraction capacity, with additional advantages in nutrient recycling, especially N and K, reducing the risk of losses through leaching (Crusciol & Soratto, 2009).…”