ABSTRACT Previous cultivation of sorghum (Sorghum bicolor), Congo grass (Urochloa ruziziensis), and palisade grass (Urochloa brizantha cv. ‘Marandu’) may influence soybean (Glycine max) agronomic performance. The present work evaluated the decomposition of sorghum, grass, and sorghum intercropped with grass in the off-season to improve soybean yield in integrated crop systems in the Brazilian Cerrado and their dry matter production. This study was conducted in Planaltina, DF, in Central-West Brazil, on a Typical Acrustox soil from Mar 2010 until Feb 2012. The experimental design was a randomized block, with six crop systems before soybean: fallowing, sorghum, palisade grass (alone or intercropped with sorghum), and Congo grass (alone or intercropped with sorghum) with four replicates. Soybean agronomic performance, the crop systems’ dry mass, and its decomposition rate were estimated over two years. Higher soybean grain yields were observed in cropping systems including Congo grass alone (3,349 kg ha–1) or intercropped with sorghum (3,317 kg ha–1). Sorghum intercropped with palisade grass produced 18,702 kg ha–1 of dry matter and 64.9 % (on average) of soil coverage during the soybean cycle. However, the highest lignin content was observed in sorghum intercropped with Congo grass (5.1 % on average). The results indicate that the cultivation of Congo grass, either alone or intercropped with sorghum, improves the agronomic performance of soybean in succession, compared to sorghum alone or palisade grass (alone or intercropped with sorghum). The intercropped systems provided the best nutrient efficiency use aiming at sustainable agriculture in the Cerrado region. bicolor, bicolor , bicolor) Urochloa ruziziensis, ruziziensis ruziziensis) cv ‘Marandu Marandu ‘Marandu’ Glycine max offseason off season production Planaltina DF CentralWest Central West Brazil 201 2012 block fallowing replicates mass years 3,349 3349 3 349 (3,34 ha1 ha 1 3,317 3317 317 (3,31 ha–1. . 18702 18 702 18,70 ha– 649 64 9 64. average cycle However 5.1 51 5 (5. average. succession sorghum. region 20 3,34 334 34 (3,3 3,31 331 31 1870 70 18,7 6 5. (5 2 3,3 33 (3, 187 7 18, ( 3, (3

ABSTRACT: Sorghum (Sorghum bicolor (L.) Moench) may be harmlessly intercropped with Urochloa species during the off-season in the Brazilian Cerrado. At the end of the sorghum cycle, forages can be used for straw production for soybean (Glycine max L.) as the summer crop. This study aimed to evaluate sorghum cultivated during the off-season, intercropped with palisade grass (Urochloa brizantha cv. ‘Marandu’ (Hochst. ex A. Rich). R. D. Webster) and Congo grass (Urochloa ruziziensis (R. Germ. and Evrard) Crins) in two row spacings (0.5 and 0.7 m) for their effect on plant growth, dry mass production, sorghum yield and soybean grain yield. The experiment was a randomized block design: a 3 × 2 factorial scheme, with three levels of intercropping (palisade grass, Congo grass or sole cropping) and two levels of row spacing (0.5 or 0.7 m) with four replicates. Several physiological growth indexes were estimated from 10 to 60 days after emergence (DAE), including dry matter production and sorghum agronomic performance. Sorghum accumulated 0.22 g of dry matter d−1 at 10 to 60 DAE, and was not affected by intercropping. The dry mass gain of forages (0.04 g d−1 on average) was not affected by sorghum either. Higher sorghum grain yield (2,922 kg ha−1) was observed under the 0.5-m row spacing when compared to the 0.7-m spacing. The results indicate that palisade or Congo grass may be used as companion crops for sorghum with no grain yield loss, be it to improve soybean grain yield, soil cover or integrated crop systems, aiming at sustainable intensification.

Resumo: O objetivo deste trabalho foi avaliar a influência de sistemas de cultivo de sorgo e plantas de cobertura anteriores ao cultivo da soja, na ocorrência de plantas daninhas durante o cultivo da soja no Cerrado brasileiro. O experimento foi realizado em delineamento de blocos ao acaso, com quatro repetições. Os tratamentos consistiram em seis sistemas de cultivo antes da soja: sorgo (Sorghum bicolor), capim-marandu (Urochloa brizantha) e capim-ruziziensis (Urochloa ruziziensis), isolados ou consorciados, além do pousio. As plantas daninhas foram avaliadas quanto a: densidade, massa de matéria seca, diversidade, valor de importância e similaridade. A maior similaridade de plantas daninhas ocorreu nos cultivos solteiros de sorgo, capim-marandu e capim-ruziziensis do que em seus cultivos consorciados. O capim-ruziziensis antes da soja favoreceu maior redução da diversidade de plantas daninhas no decorrer do tempo, quando comparado ao capim-marandu. A ausência de plantas de cobertura no pousio aumentou a infestação de plantas daninhas durante o ciclo da soja. Os sistemas consorciados de sorgo com plantas de cobertura antes do cultivo da soja influenciam a diversidade e o valor de importância das plantas daninhas.

Abstract: The objective of this work was to evaluate the influence of sorghum and cover plant cropping systems before soybean cultivation on the occurrence of weeds during soybean growing in the Brazilian Cerrado. The experiment was carried out in a randomized complete block design, with four replicates. The treatments comprised six cropping systems before soybean: sorghum (Sorghum bicolor), palisade grass (Urochloa brizantha), and Congo grass (Urochloa ruziziensis) as cover plants, alone or intercropped, in addition to fallowing. Weeds were evaluated as to: density, dry matter mass, diversity, importance value, and similarity. The greatest similarity of weeds ocurred in single crops of sorghum, palisade grass, and Congo grass, in comparison with their intercroppings. Congo grass before soybean promoted a greater reduction in weed diversity overtime, when compared with palisade grass. The absence of cover crops before soybean cultivation increased weed infestation during the soybean cycle. The cropping systems with sorghum intercropped with cover crops before the soybean cultivation affect the diversity and the importance value of weed species.

Objetivou-se avaliar a dinâmica de plantas daninhas influenciada pelo cultivo de sorgo na safrinha em dois espaçamentos entre linhas (0,5 e 0,7 m) consorciado com braquiária ruziziensis e capim-marandu e em cultivo solteiro. O experimento foi conduzido em Planaltina, DF, nas safras 2010/2011 e 2011/2012 e as avaliações realizadas durante o ciclo do sorgo na safrinhas e na soja em sucessão. Foram avaliadas a população e a matéria seca de plantas daninhas e o banco de sementes no solo durante os dois anos agrícolas. O sistema de sorgo consorciado com braquiária ruziziensis no espaçamento de 0,50 m reduziu a população de Ageratum conyzoides entre os anos agrícolas. A quantidade de sementes viáveis de Tridax procumbens no solo foi reduzida no sistema com sorgo cultivado no espaçamento 0,70 m, independente de estar consorciado ou não. O cultivo solteiro de capim-marandu na safrinha diminuiu o banco de sementes de Digitaria sanguinalis no solo. Sistemas de cultivo em safrinha com a presença de capim-marandu ou braquiária ruziziensis, solteiros ou em consórcio, apresentaram menor número de sementes de plantas daninhas viáveis no solo, indicando que essas espécies podem ser inseridas em sistemas consorciados ou em sucessão visando ao manejo integrado no sistema plantio direto.

The aim of this study was to assess the influence of short-season sorghum-grass intercropped systems on weed population dynamics. The integrated systems consisted of sorghum grown at two row spacings (0.50 m and 0.70 m), intercropped with palisade grass or Congo grass. We also used sole crops of sorghum, palisade grass, Congo grass and a fallow to serve as a reference for spontaneous vegetation. The experiment was conducted in 2010 and 2011 at Planaltina (Federal District) in Brazil. Weed populations and weed dry matter were assessed during the short season and during the succession soybean cycle. The weed soil seed bank was sampled in both years of the study. Sorghum at a row spacing of 0.50 m intercropped with Congo grass reduced the Ageratum conyzoides population. The Tridax procumbens seed bank in the soil was reduced by using sorghum at a the row spacing of 0.70 m, whether intercropped or not. Planting palisade grass during the short season reduced Digitaria sanguinalis in the soil seed bank. Planting palisade grass or Congo grass as a sole crop or intercropped reduced the number of weed seeds in the soil, showing that these species can be recommended for integrated weed management in intercropped systems.

O objetivo deste trabalho foi avaliar a produção de biomassa e cobertura do solo de diferentes espécies em sucessão ao milho cultivado nos sistemas convencional e plantio direto em condições de Cerrado. Avaliou-se a produção de biomassa de aveia-preta, crotalária júncea, feijão-bravo-do-ceará, guandu, mucuna, girassol e milheto, quando apresentavam 50% de florescimento. A cobertura do solo foi determinada aos 30 e 60 dias após a semeadura das culturas de sucessão, em agosto (período da seca), em outubro (depois das primeiras chuvas) e na cultura do milho, aos 15 e aos 45 dias após a sua semeadura. A mucuna foi a espécie que apresentou a maior taxa de cobertura do solo durante seu crescimento. A produção de biomassa do girassol não foi eficiente na cobertura do solo. O sistema plantio direto apresenta maior produção de biomassa pelas culturas de cobertura em relação ao sistema convencional.

The objective of this study was to evaluate the biomass production and soil cover by different crops after maize cultivated in conventional tillage and no-tillage, in Cerrado conditions. The biomass of black oat, sunnhep, canavalia, pigeonpea, mucuna, sunflower and millet was obtained when they showed 50% of flowering. Soil coverage was evalluated at 30 and 60 days after sequential crops sowing, in August (during dry season), in October (at the beginning of the rainy season) and after 15 and 45 days of maize crop sowing. Mucuna showed the highest soil coverage rate during its growing. The biomass produced by sunflower had no efficiency for soil coverage. No-tillage showed the highest productions of biomass by sequential crops, compared to the conventional tillage system.