Utilization of a manure compost for organic farming in Hong Kong

A manure compost has been identified as an alternative to fertilizer to increase soil fertility and crop production in organic farming. The aim of the present study was to evaluate the effects of manure compost on soil properties and crop quality as well as to determine the optimum application rate. A field experiment was carried out to evaluate the growth of Brassica chinensis and Zea mays L. on loamy soil amended with 0, 10, 25, 50 and 75 tonnes ha(-1) of manure compost. Addition of manure compost increased total organic matter, macro-nutrients (N, P, Mg, Na, Ca and K) and micro-nutrients (Cu, Zn and Mn)in the amended soils according to the rate of compost application. It also improved soil physical properties with a significant increase in soil porosity and hydraulic conductivity, but a decrease in bulk density. The dry weight yields of both plant species were higher in soils receiving manure compost amendment and plots with 50 and 25 tonnes ha(-1) compost had the highest yields of Z. malls L. and B. chinensis, respectively. An increase in dry weight yields indicated a better nutrient status in compost-amended soil which was supported by the higher tissue nutrient contents of N, P and K of plants grown in soil with manure compost amendment. However, there was also a higher accumulation of Cu and Zn in plants growing in compost-amended soil. Nevertheless, the accumulated Cd contents were all within the concentrations recommended for vegetables by the National Health and Medical Research Council, Australia. It can be concluded that the manure compost produced locally could be a suitable organic fertilizer for organic farming in Hong Kong and an application rate of 25-50 tonnes ha(-1) would give the highest crop yield. (C) 1998 Published by Elsevier Science Ltd. All rights reserved.