The experiments were conducted at the Department of Crop Science Analytical Laboratory and green house of Faculty of Agriculture, University of Nigeria, Nsukka. Experiment one was an analysis of the nutrient contents of fermented and unfermented plant waste materials using the official method of analysis of Association of Official Analytical Chemists (AOAC). Experiment two was on assessment of the effects of plant wastes and different forms of organic manure fermented for one or two months on the growth and yield of okra plants. The experiment was a split-split plot experiment laid out in a completely randomized design (CRD) with four replications. The factors were plant waste (four), particle size (two), and form (four), giving a total of thirty-two treatment combinations. The plant wastes were rice husks, moringa pod husks, grass, and control (no manure).The two particle sizes were 1.00 mm and 0.63 mm and the four types of manure were biol, biosol, biol and biosol combination and no manure. Data were collected on; number of leaves per plant, number of leaves/treatment, plant height/treatment, plant height, stem girth, stem girth/ treatment, seed weight per fruit, fruit weight, fruit girth, 100 seed weight, number of seeds per plant, average number of seeds/treatment. Data were subjected to analysis of variance (ANOVA). Mean separation was done using Fishers least significant difference. Significance was accepted at (P < 0.05).
Moringa pod had the highest nitrogen (1.30%), phosphorus (16.38 ppm), potassium (0.54 ppm) and fat content (2.65%). The biols (P < 0.05) gave the highest percentage moisture of 87.4% for rice husk, 83.28% for moringa pod husk and 85% for grass. The least percentage ash was 0.84%, 0.87% and 0.94% respectively. Fat content was considerably higher in the raw wastes than in the fermented wastes at both one month and two months of fermentation. Moisture content was generally low at 6.4%, 7.0%, and 6.85% for moringa pod, grass and rice husk, respectively. The liquid (biol) of the wastes fermented for one month differed significantly ( P < 0.05) from both the biosol and the biol + biosol combination in improving plant height, number of leaves and stem girth of okra plant starting from three weeks after planting. Thus, biol gave the best result for fruit length (5.44 cm), fruit weight(0.78 g), fruit girth(4.52 cm), number of seeds (10.33), 100 seed weight (4.32 g) and seed weight per fruit (0.46 g)( at P < 0.05) compared to biosol that gave fruit length (3.88cm), fruit weight(0.38 g), fruit girth(2.92 cm), number of seeds(5.50), 100 seed weight(2.98g) and seed weight per fruit(0.19g). For wastes fermented for two months, the biol also gave the best result for fruit length (5.87 cm), fruit weight (0.63 g), fruit girth (4.10 cm), number of seeds (12.29), 100 seed weight (2.63 g) and seed weight per fruit (0.36 g),( P < 0.05), compared to the biosol that gave fruit length (1.33 cm), fruit weight(0.07 g), fruit girth(0.83 cm), number of seeds(1.33), 100 seed weight(0.67 g) and seed weight per fruit(0.03 g)( P < 0.05). Among the three plant wastes, the solid wastes (biosols) of rice husk improved okra fruit length (4.40 cm) more than grass (2.21 cm) and moringa pod husk (2.71 cm). Particle sizes have no significant effect (p< 0.05) on the growth and yield of okra. The liquid wastes (biols) of moringa pod husk gave the best growth and yield. Generally, plant growth and yield were better for wastes fermented for one month compared to wastes fermented for two months (P < 0.05).
The environment, human health and agricultural practices are intrinsically linked: environmental quality is crucially important to agriculture because agricultural waste has the potential to harm human and pollute the environment. This means that farmers have a duty to ensure that they do not treat, keep or dispose of agricultural waste in a manner likely to cause pollution of the environment or harm to human (SEPA, 2005). In spite of the intensive use of inputs for about half a century in Nigerian agriculture, the yield gap in various crops still remains large even after following the best practices. The agricultural lands continue to shrink and there is a greater threat to global environment and soil resources. These threats are erosion of biodiversity and change of climate marching towards desertification and environmental, soil, air, and water pollution. Hence there is now a greater need to maintain the crop/soil environment by popularizing eco-friendly and cost effective organic manures (Chandrakala, 2008).
Global awareness of health and environmental issues is increasing in recent years and there is a growing demand for organically grown food products worldwide. Before the green revolution, cultivation was mostly by natural and traditional farming methods which involved natural methods of maintaining crop productivity and controlling crop pests. Consequent upon the green revolution, the use of high yielding and fertilizer responsive varieties and cultivation system were intensified and this had prompted the use of chemical fertilizers and pesticides. This indiscriminate use of fertilizers and pesticides led to several harmful effects on soil, water and the environment causing their pollution and decline in the productivity of the soil on which crops depend (Chandrakala, 2008).
A number of alternatives have been muted as means of curtailing this harmful trend, chief amongst them is a return to the traditional farming methods that use locally available raw materials as manure and the more refined organic farming system.
In fact, organic agriculture is a holistic means of farming with the aim of conserving natural resources through good agronomic practices and the use of locally available low cost inputs in order to maintain soil fertility and conserve its rich bio-diversity to provide safe clean environment and achieve economic sustainability.
Due to the prohibitive cost of chemical fertilizer, majority of Nigerian small-scale
farmers do not apply the recommended fertilizer doses. They use indigenous organic materials as source of nutrients. These organics are bulky in nature but, contain reasonable amounts of nutrients.
Organic manure is therefore the backbone of organic agriculture. Apart from its bulkiness it has been well documented that it is a slow release fertilizer with long residual effect (Chandrakala, 2008), this implies that it has a disadvantage on short term annual crops that may require quick release of plant nutrients to enable them complete their life cycle. This has necessitated research in the area of reducing its bulkiness and exploring means of hastening the release of the enormous nutrient trapped in this raw material. Apart from boosting crop yield, organic manure increases the organic matter content of soils thereby buffering the soil against changes in climate.
Important source of this organic manure include the biofuel technology, waste management plants, municipal solid wastes (MSW), landfills and composts (Sanjeet et al., 2010).
The biofuel technology aims at maximizing the energy potentials of agricultural wastes by using them in the production of biofuel and biodiesels and in return produces a digestate (organic manure) that is very rich, well cured and environmentally friendly which could be used in crop production. Hence, this work was aimed at maximising the use of plant wastes as organic manures in various forms as obtained from biogas production process with the following objectives to
1. evaluate the nutrient contents of three plant organic waste materials before and after fermentation and.
2. assess the efficacy of the three forms of organic manure (biol - the liquid part of the fermented waste, biosol - the solid part of the fermented waste and bio+biosol combination) and three plant wastes (rice husk, grass and moringa pod husk) on the growth and yield of okra