Nitrogen mineralized during sorghum growth after soil incorporation of different winter cover crops
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Growing catch crops during the autumn/winter period is a strategy of high ecological significance since it allows reducing the residual inorganic-N present in the soil after the summer season (Rodrigues et al., 2002). Thus, winter catch crops reduce the risk of denitrification and nitrate leaching associated to the excess of rain of the autumn/winter months. Incidentally, the evergreen systems confer several other additional benefits, including protection against soil erosion and increasing soil organic matter. In recent years, agronomists and soil scientists have studied the pros and cons of the introduction of cover crops/catch crops in different agro-ecological conditions and cropping systems. Some were focused in comparing the performance of different plant species when they were used as catch crops (Jensen, 1992; Chapot and Robin, 1994). In addition, since winter catch crops precedes summer cash crops, it is important to know the effect of the catch crop in the performance of the cash crop. As a general rule, the catch crop should present good growth rate in winter and improve soil fertility to promote the growth of the summer crop. Theoretically, lupine (Lupinus albus) seems to have both features. It is a species of high biomass production in autumn/winter period (Rodrigues et al., 2013) and, being a legume species with tissues of low C/N ratio, net nitrogen mineralization should occur early in the growing season of the crop that follows lupine in the rotation. In this work, results are presented of the effect of several winter cover crops in nitrogen availability in a soil cultivated with sorghum in the following summer season.
