Abstract
ABSTRACT The previous cultivation of green manures and mechanical soil decompression are options to minimize compaction of the topsoil in no-tilage system (NTS) set in different production systems in the Brazilian Savannah. In addition, it is essential to relate these agricultural practices with the economic benefits generated through the production cycles. The objective of this study was to evaluate economically the effect of sporadic mechanical decompression of the soil and previous cultivation of green manure in the production and net gain margin of upland rice and "winter" common bean, under sprinkler irrigation, in NTS in lowland Brazilian savannah. This study was developed in the 2012/13 harvest and 2013 winter in Selvíria, state of Mato Grosso do Sul, in an clay texture Oxisol in the savanah in the state of Mato Grosso do Sul, in a randomized block design arranged in a 5 x 2 factorial arrangement with four replications. The treatments were a combination of five green manures (fallow (control), Cajanus cajan, Crotalaria juncea, Pennisetum glaucum and Urochloa ruziziensis) with and without mechanical soil scarification. The yields of upland rice and common bean grains were not influenced by the previous green manure cultivation; the upland rice grown in succession to Cajanus cajan in the presence of mechanical soil scarification provided greater increase in grain yield and higher gross margin profit. Beans cultivated in succession to Crotalaria juncea and Pennisetum glaucum in the presence of mechanical soil scarification, followed by rice cultivation, provided greater increases in grain yield and gross profit margins.
Highlights
Rice and beans have economic, social and nutriton importance due to the daily consumption habit
It is found that upland rice cultivated in succession to Cajanus cajan with (6,074 kg ha-1) and without (5,154 kg ha-1) mechanical soil scarification, in addition to Crotalaria juncea with scarification (5,015 kg ha-1) provided greater increases in the yield of rice grains in relation to other green manure (GM) (Table 2)
These results evidence the potential of Cajanus cajan, regardless of scarification, in providing greater cycling and release of nutrients for rice grown in succession
Summary
Rice and beans have economic, social and nutriton importance due to the daily consumption habit. The per capita annual consumption of rice in Brazil is between 25 and 50 kg-1 inhabitant -1 year-1 (FAO, 2011), being an excellent source of carbohydrates, in its natural form, but it can be an important source of proteins, mineral salts (mainly phosphorus, iron and calcium) and vitamins of B complex such as B1 (thiamine), B2 (riboflavin) and B3 (niacin). The grain, besides being typical of the Brazilian cuisine, is a source of vegetable protein, B vitamins, mineral salt, iron, calcium and phosphorus (Brazil, 2013). In an established no-tillage system (NTS), because of the small mobilization in the soil, compactation issues have been occuring with greater intensity and extenion in in the surface layers. This occurs because of the compression process caused by machinary traffic in agricultural operations where the soil at moisture conditions above the ideal, especially in clay soils, and due to no soil mobilization, combined with higher water retention in the soil, determining a short period of time with adequate moisture for mechanized operations (Araújo et al, 2001)
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