Soil nutrients and maize yields responses to indigenous agroforestry tree post-fallows management in Tanzania

Abstract

Agriculture is characterized by low production and expansion into forests and woodlands rather than increased productivity leading to deforestation and land degradation in sub-Saharan Africa. Use of appropriate low input agricultural and other land management technologies may increase production and benefit smallholder farmers through increased productivity in already degraded land. A field experiment was established to assess tree fallows and tree coppice intercropping of indigenous agroforestry tree species (Albizia harveyi and Albizia versicolor) for soil fertility and maize yield improvements in Morogoro, Tanzania. A. versicolor tree fallows recorded significantly (p < 0.05) highest amounts of soil total nitrogen, extractable phosphorus, calcium, magnesium and potassium in 0 - 15 cm soil depth compared to the A. harveyi tree fallows and continuous cropping. A. harveyi tree fallow recorded significantly (p < 0.05) higher amounts of organic carbon and calcium than the continuous cropping system. In comparison with continuous cropping, amount of organic carbon was higher by 41% and 56% in A. harveyi and A. versicolor tree fallows, respectively. During the first cropping season, yields of grains (1.26 Mg ha−1), cobs (0.3 Mg ha−1) and stovers (2.43 Mg ha−1) in maize intercropped with A. versicolor coppices were significantly (p < 0.05) higher than those of maize intercropped with A. harveyi coppices (0.74 Mg ha−1, 0.2 Mg ha−1, 1.49 Mg ha−1) and maize in continuous cropping system (0.29 Mg ha−1, 0.06 Mg ha−1 and 1.06 Mg ha−1). During the second cropping season, yields of maize stovers, height and diameter growth were lower in intercropped maize relative to continuous cropping by 98% to 98.7%, 14.8% to 15.3% and 46.4% to 81.0% respectively; due to increasing competition imposed by growing coppices. The studied indigenous agroforestry tree species are recommended for rotational woodlots and short rotation coppice systems to enhance agricultural productivity and safeguard the environment.