Biophysical interactions in tropical agroforestry systems

sequential systems, simultaneous systems Abstract. The rate and extent to which biophysical resources are captured and utilized by the components of an agroforestry system are determined by the nature and intensity of interac-tions between the components. The net effect of these interactions is often determined by the influence of the tree component on the other component(s) and/or on the overall system, and is expressed in terms of such quantifiable responses as soil fertility changes, microclimate modification, resource (water, nutrients, and light) availability and utilization, pest and disease incidence, and allelopathy. The paper reviews such manifestations of biophysical interactions in major simultaneous (e.g., hedgerow intercropping and trees on croplands) and sequential (e.g., planted tree fallows) agroforestry systems. In hedgerow intercropping (HI), the hedge/crop interactions are dominated by soil fertility improvement and competition for growth resources. Higher crop yields in HI than in sole cropping are noted mostly in inherently fertile soils in humid and subhumid tropics, and are caused by large fertility improvement relative to the effects of competition. But, yield increases are rare in semiarid tropics and infertile acid soils because fertility improvement does not offse

Pigeonpea (Cajanus cajan L. Millsp.): An Ideal Crop for Sustainable Agriculture

Pigeonpea [Cajanus cajan (L.) Millsp.] is traditionally cultivated as an annual crop in semi-arid regions of the world. It has a number of characteristics such as diverse maturity time, drought tolerance and natural out-crossing which makes it unique among legumes. These traits not only allow its cultivation in diverse environments and cropping systems, but also permit implementation of different breeding methods. Pigeonpea is a crop of sustainable agriculture and poor crop management, exposure to diseases and pests coupled with unpredictable rains hinder crop improvement activities. However, recently partial out-crossing has been exploited to develop cytoplasmic male-sterility (CMS) based hybrid breeding technology. Thus far, three hybrids have been released for cultivation with yield advantages of 30–50% over standard varieties. Pigeonpea R&D now also enjoys a wealth of genomics resources such as a draft genome sequence, resequencing data, candidate genes and markers associated with key traits. Genomics and breeding efforts are underway to make pigeonpea a more sustainable crop and to unlock the genetic diversity present in germplasm to develop new cultivars rapidly