Municipal solid waste compost (MSWC) as a soil amendment in irrigated vegetable production

A field study was conducted to evaluate the water conservation aspects for vegetable production associated with field incorporations of municipal solid waste compost (MSWC). In June 1992, MSWC was incorporated into a sandy soil as a soil amendment at the University of Florida Gulf Coast Research and Education Center; Bradenton, Florida. Drip-irrigated and subirrigated vegetable production studies were conducted during autumn 1992, spring 1993, autumn 1993, and spring 1994 seasons. Green peppers were grown during the autumn seasons and fresh market tomatoes were produced during the spring seasons. MSWC was applied at various rates in drip-irrigated and subirrigated plots. Drip irrigation was applied based on crop water use estimated from reference evapotranspiration data and crop coefficients. A fully enclosed subirrigation system was used in the subirrigated plots with the water table controlled at an average depth of 0.60 m below the soil surface. Nitrogen fertilizer was applied to each of the MSWC drip-irrigated and, subirrigated plots. Incorporated MSWC was still immature (based on measured C/N ratios > 30) and reduced autumn 1992 drip-irrigated pepper yields and reduced plans growth. By spring 1993 the incorporated MSWC had field matured and resulted in significantly increased tomato plant size and fruit yields in the spring of 1993 and all other subsequent drip-irrigated trials. The 134 t ha(-1) MSWC rate increased spring 1993 and 1994 tomato yields by 27% and 18%, respectively and autumn 1993 peppers by 17% over the non-amended plot yields. Drip-irrigated pepper yields were not affected by irrigation rate or applied nitrogen level. While drip irrigation rate did not affect total tomato fruit yield in any of the seasons, yield of extra large tomato fruit was greater with higher levels of applied water in the spring of 1994, and the higher applied nitrogen levels increased marketable fruit yields by 13 to 14%. In general, amending a sandy soil with MSWC significantly improved plant growth and yield in drip-irrigated vegetable production. However applied nitrogen rate in the subirrigated fields did not affect fruit yield in any of the seasons. Autumn 1992 pepper yields and spring 1994 tomato yields in the subirrigated plots were reduced by the addition of MSWC and autumn 1993 pepper yields were greater with the addition of MSWC. MSWC increased yield of extra large tomato fruit in the spring 1993 season and reduced fruit size in the autumn 1993 pepper trial, but had no statistical effect on fruit size in any of the other seasons. Therefore, the subirrigated system results were not as conclusive as the drip-irrigated results. Furthermore, immature MSWC products should be incorporated into fields with sufficient maturation rime prior to planting.