Management of Legume as Land Cover Crop and Empty Bunch for the Nitrogen Efficiency in Inceptisols at Oil-Palm Plantation

Abstract

The research aimed to know the kind of legume cover crop which more suitable to be cultivated especially in area of Natar, South Lampung and to know the efficiency of N supply. It used a single Randomized Complete Block Design (RCBD) consisted of 4 treatments (several kinds of debris), covering: kacang benguk (Mucuna cochinchinensis), kacang ruji (Pueraria javanica), and oilpalm empty bunch compared to one which no debris added (control). Data analyzed by regression, F test (α 5%; or Kruskal-Wallis), DMR test (α 5%; or Mood Median) and correlation test. Result showed that Pueraria javanica (kacang ruji) was more suitable to be cultivated. Regression showed that management of empty bunch tend to enhance the ratio of NH 4 + /N-mineral as indicator of N supply efficiency, while the management of Pueraria javanica tend to decrease the ratio of NH 4 + /N-mineral. The degradation of soil NO 3 -concentration in the treatment of empty bunch was followed by the degradation of soil nitrification potential and the enhancement of heterotrofic bacteria. The enhancement of soil nitrification potential in the Pueraria javanica and Mucuna cochinchinensis management was followed by the degradation of soil pH.

Release of Ammonium-N (NH4+) and Nitrate-N (NO3-) by Different Leguminous Cover Crops (LCCs) Planted in Peat Soils

“…During the degradation process of organic materials, the release of organic acids may contribute to slight decrement of soil pH accompanied by the availability of some nutrients in the soil [7]. In addition, previous research also shows that the nitrification process contributing towards lowering the soil pH [8] which reflects the higher amount of soil ammonium-N in the treatment plots followed by the release of soil nitrate-N (Fig. 4).…”

“…Under aerobic condition, much of the soil-N is in contact with oxygen resulting in the nitrification activity by microbes (John, Samuel, James, & Werner, 2005) [15]. In addition, increase of nitrification process has led to the decrease in soil pH (Supriyadi et al, 2017) which further restricted the microbial activities in the soils (John et al, 2005) [11]. Even though the concentration is in small amount, the increasing pattern of mineral-N released by different LCCs shows the positive endurance in acidic peat soils.…”

“…Common LCCs planted in oil palm plantation include pueraria javanica, pueraria phaseoloides, centrosema pubescens, calopogonium caeruleum and calopogonium mucuinodes. Even so, different LCC was found to release different concentration of mineral-N into the soils [8]. Hence, this study aims to determine the concentration of mineral-N in form of ammonium-N (NH 4 + ) and nitrate-N (NO 3 -) released by different types of LCCs namely mucuna bracteata, calopogonium mucunoides, pueraria javanica and centrosema pubescens planted in peat soils as well as to evaluate the effects on physico-chemical properties of the soil.…”