SERAPAN NITROGEN DARI PANGKASAN POHON LEGUM OLEH TANAMAN PANGAN PADA SISTEM BUDIDAYA PAGAR

Abstract

A study to test the recovery of nitrogen released from five legume tree prunings (Calliandra calothyrsus, Peltophorum dasyrrachis, Gliricidia sepium, Leucaena leucocephala, and Flemingia congesta) was carried out in a glasshouse for 7 weeks. Results showed that the amounts of mineral-N in the soil receiving legume tree prunings ranged from 20 mg/kg soil (Peltophorum) to 37 mg/kg soil (Gliricidia). Addition of Gliricidia produced significantly (P<0.05) greater leaf area than all legumes except Leucaena at final harvest. Application of legume tree prunings or fertilizer, however, did not produce significant increases in root dry weights. Most of the N recovered by maize (90-97%) was found in the shoots. The % recovery of pruning N by maize was significantly correlated with the initial composition of the prunings. The strongest relationship, however, was generated by the protein-binding capacity of the prunings, as shown by the largest coefficients of determination. The recovery of pruning N by maize ranged from from 54% to 69% (non-leaching conditions) and 21% to 75% (leaching conditions). It was concluded that the contribution of decomposing pruning materials to improving and sustaining crop production are not only associated with their quality and with the leaching conditions but also with the method of application of the prunings in the field. Where the pruning materials are to be applied onto the soil surface as mulch, it can be expected that the amount of N release that is eventually used by the crops is much smaller than that incorporated into the soil