Nutritional quality of organic rice grown on organic composts

Abstract

The use of organic nutrient sources in improving crop quality can be a viable alternative to traditional farming. Organic farming encourages the reduction of agrochemicals and promotes soil conservation principles. Although crop quality depends on several factors, among which the nutrient source plays a great role, there is little information available on how rice quality is affected by different organic composts. Here we grew aromatic rice on two levels of four organic composts made from kudzu vine (Pueraria lobata) at 5 and 10 Mg ha−1, Urtica sp. (nettle) at 5 and 10 Mg ha−1, Lantana sp. at 5 and 10 Mg ha−1, winter weeds at 2.5 and 5 Mg ha−1, and two other organic amendments of poultry at 2.5 and 5 Mg ha−1 and farmyard manure at 5 and 10 Mg ha−1. We studied the effect of these organic sources on nutritional and physico-chemical properties, and on the cooking quality of the rice, using a fertilized, chemical treatment as positive control. Our results show that grain yield was significantly influenced by the supply of major plant nutrients. The highest rice yield of 4.0 Mg ha−1 was obtained from the inorganically fertilized treatment. The protein content in grains was the highest, 8.98%, in the inorganic treatment (100:60:40 kg N, P, K ha−1) and lowest, 7.55%, in the control. Among organic treatments, farmyard manure at 10 Mg ha−1 contributed the least in terms of the protein content of the rice (7.78%). Significantly higher iron content, of 52.2 μg g−1, was recorded with organic fertilization than inorganic fertilization (42.1 μg Fe g−1). However, inorganic fertilization was superior in terms of copper content, of 4.1 μg Fe g−1, compared with organic treatments: 3.1–4.0 μg Fe g−1. Quality attributes indicated that cooked kernel length was positively correlated with the kernel elongation ratio. Winter weed compost provided comparative benefits for rice yield (3.87 Mg ha−1) and quality in terms of protein (8.42%), iron (48.31 μg g−1) and head rice recovery (49.39%) compared with other sources of nutrients. The results of this study suggest that organic nutrient sources can perform comparatively well as regards chemical and physico-chemical properties, and cooking quality of rice, if not better in some parameters than inorganic fertilization.