Effects of four organic amendments on soil physiochemical properties and yield of maize (Zea mays) and cowpea (Vigna unguiculata) intercrop in Awka, southeastern Nigeria

Effects of four organic amendments on some soil physical and chemical properties were investigated in Awka, Anambra State in southeastern Nigeria. Over the years, use of synthetic materials in crop production has been a common practice globally. The attendant detrimental effects of the chemicals used in the formulation of these synthetics on animal and human health as well as the environment has made researchers to look out for a better agronomic practice that would not only improve productivity but at the same time sustain a healthy environment. Sole maize, sole cowpea and maize-cowpea intercrop (study area conventional practices) were planted using four soil organic amendments viz: cassava peel (CP), poultry manure (PM), pig waste (PW) and rice husk (RH) at the rate of 20 t ha–1 with the fifth as the control. The treatments were laid out in a 3 × 5 factorial in randomized complete block design and replicated four times. Data on the treatments’ effects on the selected soil physical properties (bulk density, total porosity, soil moisture) and chemical properties (soil pH, available phosphorus, cation exchange capacity (CEC), organic carbon, exchangeable bases and exchangeable acidity) were subjected to factorial analysis of variance using GenStat 2006 Edition. Results indicated that for sole maize, the amendments had significant effect onexchangeable Al3+and Na+; organic carbon, soil pH, available phosphorus and CEC but had no significant effect on Ca2+, H+, Mg2+ and K+ as compared to the control. For sole cowpea, compared to the plots with no amendment (control), all the chemical parameters analyzed differed significantly except organic carbon. Whereas, for maize-cowpea intercrop the treatments had no significant effect on Al3+, Na+, K+ and available phosphorus but differed significantly in exchangeable H+, Ca2+, Mg2+, organic carbon, soil pH, and CEC. There was a decrease in bulk density following the amendment. For sole maize, sole cowpea and maizecowpea intercrop; bulk density, total porosity and moisture content of the amended plots were significantly (p< 0.05) influenced. Organic amendments also significantly improved the growth and yield of maize and cowpea in both the sole and intercrop systems. Generally, poultry manure resulted in higher plant height,number of leaves and leaf area for maize; vine length, number of branches for cowpea as compared with other amendments. Hence, poultry manure was the most effective organic amendment in improving the soil physical and chemical properties as well as the growth and yield of cowpea and maize.
Key words: Growth, maize-cowpea intercrop, soil physical and chemical properties, soil organic amendments