Effects of Palm Bunch Ash and Mineral Fertilizer Application on Soil Chemical Properties and on the Growth, Yield and Nitrogen Fixation of Three Pigeon Pea Varieties In The Semi–Deciduous Forest Zone Of Ghana

Abstract

An experiment was conducted at the Forest and Horticultural Crops Research Centre, Kade to investigate the effect of palm bunch ash (PBA) application on soil chemical properties and the growth, nodulation, nitrogen fixation and yield of three early maturing varieties (ICPL 87091, ICPL 88034 and ICPL 88039) of pigeonpea. The experiment was conducted both in the field and in the pot. The three pigeonpea varieties were subjected to three fertilization treatments; 2 t ha–1 PBA, 20 kg ha–1 PK fertilizer and control. The experiment was laid out in split plot design with the three varieties of pigeonpea as the main plot treatments and the fertilizer as the subplot treatments. The chemical properties of the soil at the experimental site indicated that the soil was strongly acidic (pH of 5.09), high in N (0.24%), low in P (6.8 ppm) and high in exchangeable K (1 meq 100 g‒1 soil) and moderately high in Mg (1.32 meq 100 g‒1 soil). Exchangeable Ca was also low (3.56 meq 100 g‒1 soil). Fertilization had significant effects on the soil chemical properties at harvest in both the field and the pot experiments. In the field experiment, application of PBA significantly increased soil pH (5.82), P (11.18 ppm) and exchangeable cations (3.47, 4.03, 1.17 meq/100 g soil for Mg, Ca and K respectively). The control plots consistently had the lowest levels for all the nutrients. Plant height at 50% flowering was highest among the PBA treated plants (123.6cm) although there were no significant differences among the treatments. With regards to the girth, significant (p ≤ 0.05) differences were found to exist among the treatments with PBA treated plants giving the biggest girth (1.59 cm), followed by PK treated plants (1.41 cm), while the least girth was obtained in the plants within the control plots (1.18 cm). Similarly, varietal differences also resulted in significant differences in plant girth. Fertilization significantly affected nodule number with the PBA treated plants obtaining the highest nodule number per plant (41) while plants from the control plots recorded the least number of nodules (22). Nodule dry weight were also significantly affected by the fertiliser treatments with the PBA treated plants obtaining the highest nodule weight of 1.16 g while the control plants recorded the lowest weight of 0.47 g. In the field experiment, percent nitrogen fixed ranged from 20.3% among the control plants to 64.2% among the PBA treated plants with significant differences among the treatments. Nitrogen fixation in the pot experiment followed the same pattern as that of the field experiment and ranged from 39.9% in the control plants to 56.4% in PBA treated plants. In both the field and the pot experiments plant nutrient uptake varied significantly among the different fertiliser treatments with the PBA treated plants consistently having the highest plant nutrient uptake for all the nutrients while plants from the control plots had the least plant nutrient uptake. The results of the experiment indicated that neither the variety nor the fertilizer treatments had any significant effects on the grain yield of the pigeonpea. However, total dry matter yield varied significantly among the different varieties and among the different fertiliser treatments. The variety ICPL 87091 had the highest dry matter yield (7.29 t ha‒1) while the variety ICPL 88039 had the lowest dry matter yield (4.95 t ha‒1). The PBA treated plots had the highest total dry matter (7.24 t ha‒1) while plants from the control plots gave the lowest dry matter yields (4.95 t ha‒1). The dry matter harvest index varied significantly among the different varieties. Variety ICPL 87091 which had the lowest grain dry matter yield also had the lowest harvest index (0.16) while variety ICPL 88039 which had the least stover and litter dry matter yield had the highest harvest index (0.32). Based on the results it can be concluded that the application of PBA is an effective way of amending acidic soils at a relatively low cost as well as improving the growth and the grain yield of legumes. Thus in rural areas where P and K fertilisers as well as liming materials are not readily available but PBA are in abundance, farmers should be encouraged to use PBA on their farms in order to achieve higher grain yields at a lower cost, while correcting soil acidity and improving the soil fertility.