Efficacy of Organic N-Fertilizer on Maize Growth in a Vertisol and an Acrisol in the Accra Plains

Abstract

The use of inorganic fertilizers in crop production in Sub Saharan Africa is very low due to exorbitant cost. Coincidentally nitrogen which is a limiting nutrient in sub Saharan African soils is locked up in organic waste with the waste breeding flies and having become an environmental nuisance in most towns in the sub region. Composting these organic wastes to be used as organic amendment has been proposed as one of the ways of improving on the low fertility status in soils and ridding the towns of filth in sub Saharan Africa. Ecological fertilizer is an organic N fertilizer formulated by the Department of Soil Science, University of Ghana from agricultural waste for Eco Products Limited. Though the nutrient composition of the fertilizer is known, its efficacy in relation to crop production is yet to be investigated to ascertain its effectiveness and competitiveness with the traditional inorganic N fertilizer sources. A greenhouse study was, therefore, conducted to test the efficacy of Eco-fertilizer on the growth of maize on Akuse Series, Vertisol and Toje Series, an Acrisol. Exactly 8.0 and 9.7 kg respective weights of fine earth fraction of the Vertisol and the Acrisol were weighed into plastic buckets with perforated bottoms to a predetermined height of 6.2m to attain the field bulk density of the two soils. The packed soils were left undisturbed for three weeks prior to the application of treatments to allow for stabilization of microbial activity. Each soil was kept at two moisture contents of field capacity (FC) and 75% field capacity. Maize of variety Obatampa was sown at three seeds per pot and one week after sowing, two N fertilizers; one organic (Eco-fertilizer) and an inorganic fertilizer , (NH 4 ) 2 SO 4 were surface applied at three rates of 0, 20 and 40 kg/ha. Each treatment was replicated three times and the pots were arranged in a randomized complete block design pattern, giving a 2×2×2×1×3x3 factorial experiment. Sampling of soils was done at 28 and 65 days after sowing, after which the soils were tested for NH 4+ and NO 3- . Agronomic parameters such as chlorophyll content, leaf area index, plant height at 28 and 65 days after sowing at the two moisture levels were also measured. Net assimilation rate was estimated and dry matter yield measured after 65 days of sowing. Results of the study showed that leaf area index, dry matter yield, total nitrogen content of the maize plant, net assimilation rate, plant height and chlorophyll content increased with fertilization of the two soils for both fertilizers. When the two soils were amended with the fertilizers, LAI at 28 days after sowing (LAI-1) was higher in the Akuse series than the Toje series at the two moisture contents due to the superior inherent fertility of the former soil. The higher LAI-1 in the Akuse soils is also supported by the higher available N in the soil at 28 days after sowing which also tied in very well with higher chlorophyll content at 28 days after sowing. At 20 kg/ha for the Akuse series, the nitrogen content in the plant was higher in the inorganic amended soil than that of the organic amended one. However at 40 kg/ha the nitrogen contents of the plants were statistically the same. In the Toje series, the nitrogen content of the plants at the two rates of application, irrespective of fertilizer type were similar just as dry matter yield (DMY).Similar growth parameters such as LAI, height and DMY at both 28 days and 65 days of sowing in the organically and inorganically amended Toje soil and the fact that there was generally no difference in DMY in the two soils at the two application rates indicated that the organic fertilizer competes favourably with the inorganic one in maize growth. There was generally no difference in moisture content at FC and 75% FC on N accumulation and hence DMY of maize plants after 65 days of sowing. At 28 days after sowing which is the vegetative stage of the maize plant, the NH 4+ contents in the soils was higher at 75%FC than at FC suggestive of the fact that more NH 4+ had been absorbed at FC due to the prevailing optimum condition for N absorption