Abstract
Short term changes that occur in soil properties of an ultisol under different pigeon pea hedgerow alley populations and inter-hedgerow alley spacing and the effect of such changes on ginger rhizome yield response were evaluated in a two-year (2010 and 2011) field study in South Eastern Nigeria. Treatments comprised pigeon pea hedgerow alley populations of 20,000, 33, 333 and 66, 667 plants/ha in factorial combinations with three inter-hedgerow alley width spacing of 1, 2 and 3 m in a randomized complete block design with three replications. A plot having no pigeon pea component but planted to sole ginger constituted the control. Relative to the control, growing ginger in-between pigeon pea hedgerow alleys resulted in significant improvement in soil exchangeable Ca, Mg, and K, base saturation, organic carbon and available P in addition to reducing soil dry bulk density. Highest response in soil available P, organic carbon, dry bulk density, exchangeable Ca and Na and pH was achieved using pigeon pea population of 66, 667 plants/ha, while highest response for soil total N, base saturation and exchangeable K was achieved with 20,000 pigeon pea plants/ha. Optimum ginger rhizome yield response comparable with the control was achieved using pigeon pea hedgerow alley population of 20,000 plants/ha spaced 3 m apart. Increasing pigeon pea hedgerow alley population beyond 20,000 plants/ha and decreasing pigeon pea inter-hedgerow alley width below 3 m resulted in rhizome yield reduction due to probable nutrient competition. Apart from its capacity to continuously maintain the fertility of the fragile and infertile soils of South Eastern Nigeria, planting ginger in-between pigeon pea hedgerow alley will also serve as additional source of revenue to smallholder resource-poor ginger farmers in Nigeria. Key words: Soil fertility, pigeon pea, hedgerow alley, ginger yield, South Eastern Nigeria.
Highlights
Among the three inter-hedgerow alley widths evaluated, highest significant mean dry soil bulk density reductions of 44 and 36% relative to the control were obtained on plots that had pigeon pea alleys spaced 1 m apart for 2010 and 2011, respectively
Averaged over the three pigeon pea hedgerow alley populations tested, the result of this study indicated that growing ginger sole without pigeon pea hedgerow inclusion resulted in significantly lower soil organic carbon content at 6 and 8 months after planting of ginger (MAP) compared to when it was grown in alleys formed by pigeon pea
Growing ginger in between pigeon pea hedgerow alleys resulted in significant improvement in the nutrient status of the highly degraded soils of South Eastern Nigeria
Summary
One of the greatest challenges facing agriculture in the tropics is the need to develop viable farming systems capable of ensuring increased and sustained crop production with minimum degradation of the non-. Efforts to minimize excessive use of inorganic fertilizers in tropical agriculture have led to the development of alternative farming systems such as alley cropping which is believed to have the capacity to minimize environmental C and N losses (Ansgar et al, 2009). The underlying scientific principle of this technology is that, by continually retaining fast-growing, preferably nitrogen-fixing, trees and shrubs on crop-producing fields, their soil-improving attributes (such as recycling nutrients, suppressing weeds, and controlling erosion on sloping land) will create soil conditions similar to those in the fallow phase of shifting cultivation (Nair, 1993). Several studies (Kang and Ghuman, 1991; Simpson and Wickham, 2007; Nwite et al, 2008) have demonstrated significant positive effects of alley cropping on soil fertility parameters such as organic C levels, total N and extractable P levels over a range of climatic and soil conditions
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