Abstract
The experiments were conducted at two locations-RDRS agriculture farm, Manthana, Rangpur and farmer's field of Gangahari village, Gangachara upazila, Rangpur during the period from July 2006 to February 2009. The objectives of the study were (i) to identify the optimum dose of MSWC in combination with chemical fertilizers for the T.Aman rice-Potato- Boro rice cropping pattern; (ii) to study the effects of MSWC and fertilizers on the yield parameters and nutrient uptake of crops and (iii) to determine the effects of MSWC and fertilizers on the properties of post harvest soils. T.Aman rice, Potato and Boro rice, cultivated in a 3- year crop season, were used as test crops. The field experimental design was a split plot with three replications. There were five levels of chemical fertilizers at the rates of 0, 50%, 75%, 100% NPK and farmer's practice as main plots, and four levels of MSWC applied at rates of 500, 750 and 1000 Kg ha' for first two years as subplots. In 3rd year, MSWC rates were changed to 0, 1000, 1500 and 2000 Kg ha'. MSWC were applied 7 days before transplanting of each crop season. Soil, rice grain and potato tuber samples were collected for chemical analysis as per need of the objectives. Grain yield of T. Aman and Boro rice and tuber yield of potato significantly increased due to various levels of chemical fertilizers, MSWC and their interactions. At both locations, the highest grain yield of T. Aman rice was recorded with the application of 75% NPK in every year. For the application of MSWC, grain yield considerably increased with increasing rates of MSWC application in every year. Maximum grain yields were obtained with application of 1000 Kg MSWC ha1 in 2006 and 2007 of T. Aman rice cultivation season. In 2008, 2000 Kg MSWC ha' treatment resulted in maximum grain yield. The application of chemical fertilizers in combination with MSWC further enhanced the grain yield. Hence, chemical fertilizer MSWC interaction showed better T. Aman rice production performance than their individual dose. The highest grain yield was recorded in 75% NPK × 1000 Kg MSWC ha' interaction for the year 2006 and 2007. In 2008, either 75% NPK × 2000 Kg MSWC ha1 or 100% NPK × 1000 Kg MSWC ha interaction gave statistically similar but maximum grain yield of T. Aman rice at both locations. At both locations, in all years, the highest tuber yield of potato obtained with the application of 100% NPK. For MSWC levels, 1000 Kg MSWC ha' gave maximum tuber yield. Among the interactions, 100% NPK × 1000 Kg MSWC ha1 interaction gave the highest tuber yield of potato. At both locations, the plots that fertilized with 100% NPK gave the highest grain yield of Boro rice in all years. For MSWC, plants from 1000 Kg MSWC ha' amended plots gave maximum grain yield. The 100% NPK × 1000 Kg MSWC ha interaction demonstrated maximum grain yield of Boro rice in every year. Productivity of T.Aman rice-Potato-Boro rice cropping pattern was found superior for the plots fertilized with 100% NPK, 1000 Kg MSWC ha1 and 100% NPK × 1000 Kg MSWC ha1 interaction for all cycles and years. The 75% NPK × 1000 Kg MSWC ha interaction found more profitable in terms of gross margin for T. Aman cultivation during 2006 and 2007, and 75% NPK × 2000 Kg MSWC ha interaction found superior in 2008 at both locations. For potato and Boro rice cultivation, 100% NPK × 1000 Kg MSWC ha' interaction found more economical in term of gross margin for all years at both locations. Annual return was also observed from 100% NPK × 1000 Kg MSWC ha1 interaction for all cycles compared with their single rate. Total NPKS uptake by T. Aman rice increased due to application of 75% NPK, 1000 Kg MSWC ha1 and 75% NPK × 1000 Kg MSWC ha1 interaction in 2006 and 2007. In 2008, 75% NPK × 2000 Kg MSWC ha1 or 100% NPK × 1000 Kg MSWC ha1 interaction showed higher NPKS uptake. For potato and Boro rice cultivation, NPKS uptake was higher for 100% NPK, 1000 Kg MSWC ha' and 100% NPK × 1000 Kg MSWC ha' in all years. Yearly NPKS uptake from cropping pattern was greater for 100% NPK, 1000 Kg MSWC ha1 and 100% NPK × 1000 Kg MSWC ha' interaction in all cycles. The NPKS content of post harvest soil (after 3 years) has been deteriorated over the years due to rice-potato-rice intensive cropping system with the exception of K only. The OM build up of post harvest soil was also not impressive even after application of higher level of MSWC (2000 Kg MSWC ha1) included in the experiment. There was a positive and linear correlation among nutrient uptake, soil content and yields of T.Aman, potato and Boro rice in all years. The MSWC increases NPKS uptake and soil content means high efficiency indicating less application of chemical fertilizers particularly T. Aman rice and therefore environment friendly. A clear indication of addition of MSWC along with chemical fertilizers was revealed as the potential option for sustainable farming.