<b>Biological soil loosening by grasses from genus Brachiaria in crop-livestock integration

Abstract

ABSTRACT. Soil compaction associated with pastures degradation can decrease animal productivity, forage longevity and compromise environmental sustainability. To confront this serious issue, the loosening potential of forages should be recognized. We evaluated the least limiting water range as indicator of biological loosening potential in relation to cultivation of grasses the genus Brachiaria in crop-livestock integration. We also evaluated the water availability to soybean crop that succeeded these grasses. Our studies were performed in two stages. In the first stage, we divided 32 plots into four randomized blocks in which we cultivated corn combined with following treatments: 1 -Brachiaria brizantha cultivar Marandu; 2 -Xaraes; 3 -Piata; 4 -MG4; 5 -B. decumbens; 6 -B. ruziziensis; 7 -Invasive plants; and 8 -uncovered soil. We evaluated soil, to quantify the biological soil loosening, and also forages. In the second stage, we cultivated soybean and added: 9 -conventional tillage as a control treatment, increasing number of plots to 36. Our results suggest that it is possible to cultivate Brachiaria brizantha or Brachiaria decumbens as management strategy to aid edaphic recovery. Xaraes and Piata grasses provide greater soil loosening while increasing water availability to successive soybean crop.Keywords: pasture recovery, soil structural quality, least limiting water range.Descompactação biológica do solo por capins do gênero Brachiaria em Integração Agricultura-Pecuária RESUMO. A compactação do solo associada à degradação das pastagens reduz a produtividade animal e da forrageira e compromete a sustentabilidade ambiental. No enfrentamento desta grave questão, faz-se necessário o conhecimento do potencial de descompactação do solo promovido por algumas forrageiras. Este trabalho objetivou avaliar o intervalo hídrico ótimo como indicador da descompactação biológica do solo decorrente do cultivo de capins do gênero Brachiaria em integração agricultura-pecuária, bem como a disponibilidade hídrica à soja cultivada em sucessão. O estudo foi realizado em duas etapas. Inicialmente foram implantadas 32 parcelas em quatro blocos casualizados, cultivando milho consorciado com os seguintes com os tratamentos: 1 -Brachiaria brizantha cultivares Marandu, 2 -Xaraes, 3 -Piata e 4 -MG4, 5 -B. decumbens, 6 -B. ruziziensis, 7 -Plantas invasoras e, 8 -Solo descoberto. Foi avaliado o solo para quantificação da descompactação biológica, e também as forragens. Na segunda etapa cultivou-se soja, acrescentando-se como tratamento testemunha: 9 -plantio convencional, totalizando 36 parcelas. Os resultados sugerem o cultivo de B. brizantha ou B. decumbens na recuperação edáfica. Destacam-se os capins Xaraes e Piata que proporcionaram maior descompactação do solo e, consequentemente, aumento da disponibilidade hídrica à soja em sucessão.Palavras-chave: recuperação de pastagens, qualidade estrutural do solo, intervalo hídrico ótimo.

Crop-livestock integration and the physical resilience of a degraded Latosol

“…The water content at which the resistance to the critical penetration of 2.5 MPa is reached (θ PR ) affects most LLWR amplitudes because it is a dynamic property associated with soil compaction (VAZ et al, 2001;DEXTER et al, 2007). In contrast, the minimal aeration porosity of 10% did not limit the LLWR in any treatment or layer due to the porous character of Red Latosols, the predominantly oxidic mineralogy and granular structure of which confer the soil with high structural stability and friability, reflecting the agglutination of the solid fraction of the soil and interconnected pores (REATTO et al, 2009;SEVERIANO et al, 2013;FLÁVIO NETO et al, 2015).…”

“…These effects were partially circumvented by the C4 photosynthetic apparatus, which guarantees the better use of incident radiation and more efficient water use (SAGE;ZHU, 2011;GUENNI et al, 2002). These characteristics were enhanced when breeding these cultivars, notably the Xaraés and Piatã palisadegrasses, and thus the higher metabolic activity during the dry off-season in the Brazilian Cerrado contributes to the growth of the root system, allowing the disruption of the compacted soil layers that are usually found in agricultural areas, as evidenced by Flávio Neto et al (2015).…”

“…In contrast, structural changes can occur in a short time, both in terms of degradation, if the pressure applied by machinery and grazing animals overcome the soil load bearing capacity (ZINK et al, 2010;SEVERIANO et al, 2013), and the recovery via mechanical or biological loosening (SEVERIANO et al, 2010;FLÁVIO NETO et al, 2015). Such findings are essential for the interpretation of the results presented below given the importance of root growth and organic matter in soil aggregation (BRANDÃO; SILVA, 2012).…”

“…For comparison, we adopted the following as control treatments: (6) no cultivation of Brachiaria, leaving the soil fallow and with weeds (Fallow), and comprised predominantly of a canopy of dicot weeds in terms of density and diversity, as described by Flávio Neto et al (2015) and (7) conventional tillage, which was performed by mechanical recovery via ploughing and harrowing the soil with a rotary tiller (CT) during the implementation of the subsequent agricultural calendar at the end of the cultivation of the off-season pastures in the integrated treatments. This operation was carried out when the soil water content was close to field capacity.…”

“…In addition, these species can promote biological soil loosening (SILVA et al, 2014;FLÁVIO NETO et al, 2015), minimizing compaction by machinery traffic and animal trampling, especially that managed under no-tillage and promoting nutrient cycling (PACHECO et al, 2011) and the production of straw (NUNES et al, 2006), which has enabled the adoption of integrated production systems in tropical conditions of the Brazilian Cerrado. For these reasons, Brachiaria pastures are noteworthy, especially those containing the species B. brizantha, B. decumbens, and B. ruziziensis.…”