Abstract
A study was undertaken at Agricultural Research Station (ARS), Pabna during 2000-2002 to evaluate the efficiency of different composting techniques and their effects on the yield and quality of rice and stem amaranth. Four methods viz, effective microorganisms (EM), heap(HC), vermicompost (VC) and biogas slurry (BGS) were tested against traditional ditch. method. A 50:50 cowdung and town wastes were used as substrate. Performances of rice and stem amaranth crops were tested with sole and combined uses of composts against 100% chemical fertilizers and control. Their residual effects were studied in the next crops. ps. A second stock of active compost was prepared with poultry based substrates. Rice and stem amaranth crops were treated with 7.5, 15, 22.5 and 30 t ha1 sole composts and same compost doses with 60, 50, 40 and 30% urea N; 10 t ha1 compost with 50% chemical, 5 t ha1 compost with 70% chemical, 50, 70 and 100% sole chemical fertilizers. Soil and plant analyses were done for physical and chemical characters. Sensory test was done for determining taste differences of cooked foods.
Heap method was found to be better considering the nutrient contents, crop response and easiness in preparation. EM method was the most rapid one. Stem amaranth responded better than rice under compost treatments. The yield increase in sole compost treatments against control reached to 38 and 406% in rice and stem amaranth at the end of second and third crops, respectively. The residual effects of sole composts produced 23 and 14% higher rice yield and 269 and 37% stem amaranth yield over control and chemical fertilizer treatments, respectively. With the increased compost doses, rice yield increased up to 15 t ha1 and then declined. But when used with urea N yield increased up to 22.5 t ha1 and then declined slightly. In stem amaranth, the plant yield increased steadily with the increase in compost doses as sole or with urea N.
After last crops of each experiment soil moisture contents increased up to 13.3% compost treatments and bulk density decreased. Soil pH decreased slightly. Soil organic matter content increased up to 37% after rice and 54% after stem amaranth due to compost use. Contents of total N and available P and Zn were increased due to compost treatments. Exchangeable K and available S contents remained unaffected.
Apparent nutrient balance with N was negative except with sole composts and that of P, K and S were positive with use of composts and prominently with higher compost doses. Crop uptake of N, P, K, S and Zn were higher with chemical fertilizers used as sole or in combination with composts.
An increase of 11 and 24.5% of protein in rice grain was found in sole compost treatments and 30 t ha1 compost rate, respectively. Amylose content of rice grain was higher with sole compost. Vitamin C content decreased and carotene content increased up to 39% due to compost use in stem amaranth. The Ca and Fe contents were sharply increased in stem and leaves of stem amaranth due to compost use and drastically reduced with the use of chemical fertilizers. Heavy metal like Pb and Cd contents in plants were not influenced by compost or chemical fertilizer treatments.