Assessment of Nutrient Flux Through Runoff Water from Forest Ecosystem for Crop Production in Agroecosystem in Himalyan Watershed

摘要

The analysis of runoff water from Henwal river watershed (550hac) having 34.8%, 3.0% and 62.3% area under cultivable, pasture and forest lands, respectively revealed that the concentration of nutrients was highly variable during different weeks and months. Ca~(2+), NO~(3-) and CO_3~(2-) were recorded highest in September; Mg~(2+), NO~(3-) and HCO~(3-) in August; K~+ and PO_4~(3-) in July; Na~+ and SO_4~(2-) in June and Cl~ in October. The order of dominance of cations was Ca~(2+) > Mg~(2+) > Na~+ > K~+ and that of anions was HCO~- >CO_3~(2-) >Cl~- >NO~(3-) >SO_4~(2-) >PO_4~(3-) .An estimate of individual ions in runoff water indicates that HCO_3 and CO_3~(2-) constituted about 60%, Ca~(2+) and Mg~(2+) 20%, Cl~- 10% and remaining ions 10% of the total ions. Litter biomass was recorded highest in oak-mixed litter under forest and lowest in deodar. C:N ratio of 30:1, 32:1 and 47.1 was recorded in oak-mixed, deodar and pine forest ecosystem, respectively. Litter under oak-mixed forest contained highest amount of Ca, Mg and K while deodar and pine had N and P contents. NO_3~-, K~+ and CO_3~(2-) in runoff water was highest in deodar, Ca~(2+), Mg~(2+) and K~+ in pine while PO_4~(3-) and HCO_3~- in oak-mixed forest ecosystem. The contribution of runoff water on pod yield of vegetable pea was 16.7, 31.1 and 24.2%, respectively from deodar, pine and oak-mixed forest ecosystem. The response of NPK at 50 and 100% of recommended dose with runoff water was comparable to each other. Nutrient use efficiency (NUE) under 50% NPK with runoff water was highest and declined sharply at 100% NPK. Further, NUE was highest in deodar as compared to pine and oak forest ecosystems. There was a considerable improvement in amounts of organic C, available N, P and K status of soil with runoff water treatment. Thus forest litter and runoff water in hill and mountain ecosystem are the major pathway of nutrients to meet the crop requirements in agro ecosystem.