Effect of Pigeon Pea-Groundnut Intercropping System on Selected Soil Properties

On average Malawi is losing of 40 kg N ha-1 and 6.6 kg P ha-1 annually. Additionally, nutrient use efficiency (NUE) is low as a result of declining levels of soil organic matter (SOM) and associated deficiencies of other macro and micronutrients. This is usually below 20 kg maize grain kg-1 of nutrients applied. To investigate on the possibility of improving NUE a study was initiated in the 2011/12 cropping season with a parallel trial mounted along side in the second season, both were laid in a randomized complete block design replicated three times. The trials involved planting of pigeon pea as monocultures or as intercrops. The main trial had eight treatments while the parallel trial had ten treatments. After the first season legume biomass in some plots of the main trial was buried into the soil. Soil characterization was conducted before treatment application in the first and second year. Data were analyzed using genstat and subjected to analysis of variance at 5% level of confidence. Means were separated using the least significant difference. Generally, the soil chemical characteristics for soil samples collected in all the treatment plots both in the main and parallel trial indicate that the soil has low fertility. The organic carbon (OC), cation exchange capacity CEC (NH4OAc), and total N (%) was low, and was at 1.4 %, 3.5-3.6 cmol (+)/kg soil, 0.12%, while available phosphorus (Mehlich 3) was marginally adequate (mean=21.5 mg kg-1 and 22.1 mg kg-1). The soil texture which was predominantly sandy clay loam to sandy clay coupled to the low CEC suggest potential high leacheability of nutrient elements more especially nitrogen as nitrate. Inevitably, if the soil is not properly managed crop yield could be reduced drastically.