Impact of planted fallows and a crop rotation on nitrogen mineralization and phosphorus and organic matter fractions on a Colombian volcanic-ash soil |
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Authors: | T A Basamba E Barrios B R Singh I M Rao |
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Affiliation: | (1) Department of Plant and Environmental Sciences, Norwegian University of Life Sciences, P.O. Box 5003, Aas, N-1432, Norway;(2) Tropical Soil Biology and Fertility (TSBF) Institute, Centro Internacional de Agricultura Tropical (CIAT), Apartado Aéreo, 6713 Cali, Colombia |
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Abstract: | Soil fertility replenishment is a critical factor that many farmers in the tropical American hillsides have to cope with to
increase food crop production. The effect of three planted fallow systems (Calliandra houstoniana-CAL, Indigofera zollingeriana-IND, Tithonia diversifolia-TTH) and a crop rotation (maize/beans-ROT) on soil nitrogen mineralization, organic matter and phosphorus fractions was compared
to the usual practice of allowing natural regeneration of native vegetation or natural fallow management (NAT). Studies were
conducted on severely degraded Colombian volcanic-ash soils, 28 months after fallow establishment, at two on-farm experimental
sites (BM1 and BM2) in the Cauca Department. Tithonia diversifolia had a significantly higher contribution to exchangeable Ca, K and Mg as well as B and Zn; the order of soil nutrient contribution
was TTH > CAL > IND > NAT > ROT. On the other hand, lND had significantly higher soil NO3−–N at both experimental farms as compared to all the other fallow system treatments. For the readily available P fraction,
CAL and ROT had significantly higher H2O–Po and resin-Pi, respectively, in the 0–5 cm soil layer; whereas TTH showed significantly higher values for both H2O–Po and resin-Pi in the 5–10 cm soil layer. Significant effects were observed on the weights of the soil organic matter fractions
which decreased in the order LL (Ludox light) > LM (Ludox intermediate) > LH (Ludox heavy). Indigofera zollingeriana showed greater C, N and P in the soil organic matter fractions than all the other fallow treatments, with NAT having the
lowest values. It is concluded that planted fallows can restore soil fertility more rapidly than natural fallows. |
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Keywords: | Calliandra houstoniana Indigofera zollingeriana Nitrogen mineralization potential Phosphorus fractions Planted fallows Residual effect Soil organic matter fractions Tithonia diversifolia Volcanic-ash soil |
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