Temporal effect of the soybean cultivation in the physical-chemical properties of the Mato Grosso state soil. / Efeito temporal da cultura da soja nos atributos físico-químicos do solo no Estado do Mato Grosso

AUTOR(ES)
DATA DE PUBLICAÇÃO

2007

RESUMO

Humanity as we know today is totally dependent in the large scale agriculture. We are getting close to the point where it will no longer be possible to expand or substitute agriculture areas. Making an evaluation of the agriculture system sustainability very important, to verify if they are fit to maintain there function as a food provider for a growing population. This work focus on the soil physical and chemical aspect with a restricted vision on the internal farm process, without an evaluation of the entire production chain. The object off this work was to study the temporal effect of the soybean cultivation in the physical and chemical soil properties when a typical Cerrado vegetation is replaced by agriculture. Five agriculture areas with different cultivation time, i.e. 4 years (C4D3), 12 years (C12D5), 13 years (C13D12), 14 years of grain production and 8 years of pasture (C14P8) and 23 years (C23D12) where compared to a nearby Cerrado plot. All plots had the same soil type (LATOSSOLO VERMELHO-AMARELO distrófico de textura argilosa) and relief, being the maximum distance between plots 3.4 km. They all belong to the same farmer located approximately 30 km south of the city Sorriso in the Mato Grosso state (12º 42` 41`` S 55º 53` 38`` W). In each plot five soil sampling pits where made, soil sampling was done at the 0-5, 5-10, 10-20, 20-30, 30-50, 50-75 and 75-100cm depth. All major nutrients, with the exception off hydrogen, oxygen and sulfur and all minor nutrient, with the exception off chlorine and molybdenum where analyzed. Soil texture and 13C natural abundance, that permitted the calculation off the C3 plants carbon (CC3) and the C4 plants carbon (CC4), was also determined with this results the carbon (C), CC3, CC4 and nitrogen (N) stocks was calculated. The total C stock from 0 to 100cm increased with the cultivation time at a average rate of 0.8 Mg C ha-1 year-1, and on plot with the greatest accumulation (C23D12) the rate was 1.09 Mg C ha-1 year-1. A significant part off this accumulation was due to the CC4 contribution with an average rate off 0.77 Mg CC4 ha-1 year-1 in the 0 to 50cm profile. The CC3 stock in the 0 to 100cm profile did not correlate with the cultivation time, being the extreme points the C14P8 with a depletion off -0.41 Mg CC3 ha-1 year-1 and the C23D12 with a accumulation off 0.52 Mg CC3 ha-1 year-1. This shows that a replacement off the original Cerrado CC3 by the agriculture CC4 (maize) occurred, but that in some areas a accumulation off soybean CC3 also took place. The N stock variation did not correlate with the cultivation time, probably a different variable not measured in this study is driving this element. Soil cultivation increased the pH and phosphorus, potassium, magnesium, calcium, boron, zinc and copper soil concentration. Other elements such as iron , manganese and aluminum decreased with the soil cultivation. In the carbon and nutritional balance the agriculture system adopted maintained the soil original qualities and even increase the concentration off some elements. Showing that within the internal soil nutritional balance the system is sustainable.

ASSUNTO(S)

soil cronossequências solos - propriedades físicoquimico. isótopos physical and chemical properties soybean mato grosso carbon carbono soja 13c abundance.

ACESSO AO ARTIGO

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