Author:
STUDDERT GUILLERMO ALBERTO.
Year:
2005.
University:
LLEIDA [
www.udl.es].
Place of defense: ESCUELA TÉCNICA SUPERIOR DE INGENIERÍA AGRARIA.
Place of preparation: ESCUELA TÉCNICA SUPERIOR DE INGGENIERÍA AGRARIA (UNIV. LLEIDA) FACULTAD DE CIENCIAS AGRARIAS (UNIV. MAR DEL PLATA).
Summary: A sustainable production system should aim to maintain or improve the condition of your soil. The crop rotation influences of soil processes that determine their status and their productivity, and the dynamics of carbon (C) and nitrogen (N) of great importance to his definition. For soils in the southeast of the Province of Buenos Aires (Argentina) are not subject to erosion, which is hipotetizó: 1 - The crop rotation is a useful tool for maintaining agricultural sustainability even with the use of tillage conveniconal (LC). 2 - The inclusion of periods in a low pasture rotation allows recompose soil properties affected by agriculture conveniconal. 3-In rotations cultivos-pastura, it is possible to define a minimum period under pasture and a maximum low agriculture conveniconal to maintain soil properties within limits of variation consistent with the sustainability of the system. 4-In the periods under agriculture conveniconal, the variation of the content of organic matter (OM) soil can be handled through the choice of crops to be included in the rotation and nitrogen fertilization. 5 - The extension of the seasonal agricultural produce depression in crop yields of wheat (Triticum aestivum L.), associated with changes in the content of MO and the ability of the soil to provide N cultivation. 6 - The variation in the availability of N for wheat associated with conventional agriculture, can be handled through the election of the crop which precedes in the rotation. On a typical complex Argiudol and Paleudol Petrocálcico not subject to erosion in Balacarce (Argentina) (37Â º, 45'S, 58Â º 18 'W), has had two long-term trials between
1976 and 1993 a and 1984 and 1996, another , which implemented various crop rotations and sequences under LC. We evaluated the variation of the content of MO and other soil properties and the impact of the combination of crops in time on the variation in yields of wheat. The content of the topsoil MO soil decreased 12% after 6 to 7 years of agriculture and regained its original level after 3 to 4 years of pasture. The C in the light fraction, the N in microbial biomass and the rate of stable aggregates fell sharply during the period of agricultural (97-100% of the total variation estimated) and were recovered during the period under pasture. On the other hand, pure farming systems showed that over 11 years of farming, the decline in the MO of the topsoil (11 to 23% without Ny 7 to 19% with N) varied with input from the waste soil determined by the mix of crops and nitrogen fertilization. Losses increased when MO soybean (Glycine max (L.) Merr.) Was present in the stream and fell when the maize (Zea mays L.) was present because of their different volumes of waste. In addition, the increased frequency of laboreos in times of increased temperature affected the relationship between the input of waste and variation in soil MO. While the sequence of crops determined the level of M0 soil and thus its ability to mineralizar N (potentially mineralizable N, NO), it was demonstrated that the dynamics of N availability for the wheat crop was defined by the predecessor to through the effect of the characteristics of its waste. Regardless of N0, waste relationship low C / N (C: N) (pede soybeans) were associated with increased release of N for wheat stubble while high C: N (pede maize) provoked an intense immobilization that prevented the N0 available for wheat when required. These relations were strong enough to enmasca 8 rar e 608 fecto long-term sequences on the MO of soil and its N0. The performances were strong enough to mask the long-term impact delas sequences on the MO of soil and its N0. Yields on wheat fell over the period agricultural like the content of MO layer aable, but the magnitude of the decline was governed by the influence of waste on the short-term dynamics of N rather than the the ability of the soil to supply it. There was not sufficient evidence to reject the assumptions made, but it must be clarified that the effect of conventional agriculture on some properties of topsoil can have serious consequences for those susceptible to degradation mechanisms such as erosion and so on sostenbilidad System.
