Aktivitas β-Glukosidase pada Beberapa Kelas Penggunaan Lahan Gambut Tropis di Pesisir Selatan, Sumatera Barat

Most of the peatlands in Pesisir Selatan, West Sumatra have been converted into agricultural activities. Due to drainage, the peat decomposition process becomes faster. The activity of β-glucosidase is one of the enzymes that can be used as an indicator of the decomposition of organic matter and produces greenhouse gas emissions, likes CO2. Therefore, this study was conducted to identify the activity of β-glucosidase in several land uses in Pesisir Selatan peatlands. Observations were performed in several land-use types consisting of agricultural land (LP), bare land (LT), shrubs (SB), smallholder oil palm plantations (PSr), private company oil palm plantations (PSs), and forests (H). The activity of β-glucosidase was analyzed by using salicin and Na-acetate methods. The results of this study showed that the highest β-glucosidase activity was found in agricultural land use (LP). Based on the land use types, the activity of β-glucosidase follows agricultural land (LP) 3.42 μg.g-1.jam-1 > bare land (LT) 2.26 μg.g-1.jam-1 > shrubs (SB) 1.63 μg.g-1.jam-1 > smallholder oil palm plantations (PSR) 1.31 μg.g-1.jam-1 > private company oil palm plantations (PSs) 1.28 μg.g-1.jam-1 > forest (H) 0.80 μg.g-1.jam-1. Soil characteristic that significantly affects enzyme activity is water content where the higher the water content, the lower the β-glucosidase activity, and vice versa. Based on this study can be concluded that the change in land use from natural land to agricultural land triggers an increase in the activity of enzymes in decomposed peat materials.Key words: β-glucosidase, enzyme, palm plantation, land-use, peatlan

EFEK SISA ASAM HUMAT DARI KOMPOS JERAMI PADI DAN PENGELOLAAN AIR DALAM MENGURANGI KERACUNAN BESI (FE) TANAH SAWAH BUKAAN BARU TERHADAP PRODUKSI PADI

Fe toxicity on recent ricefield has been common problem in ricefield management to increase rice productivity. Adding organic matter like humic acid from any source (such as hay residue compost) and water management (intermitten flooding and continue flooding) can reduce Fe toxicity and it will be able to increase rice yield in one plant season.  But how about in second plant season, this research will found effect of adding humic acid from hay compost residue and water management. The objective of this research was to study the interaction of hay compost humic acid residue effect and water management  on Fe abundant and nutrient uptake and rice yield in recent ricefield.  This research has done by split-split plot design 2 x 4. The main plot which was treatment of water management were permanent flooding and intermitten (P1 and P2). And the  split plot which was  humic acid treatments were Ao = 0 ppm (0 Kg humic acid /Acre), A1= 200 ppm (400 Kg humic acid/A), A2= 400 ppm (800 Kg humic acid/A), A3 = 600 ppm (1200 Kg humic acid /A). Data analysed by statistical methode, if the treatments were significant to be continued by Duncan 05 % analysis.  The result has obtained of this research which was Eh value of soil in flooding and intermitten was decrease in every week because treatment of humic acid in first season. The content of Fe2+ in soil was increase in every week until the 8th week. Value of soil pH until 8th week flooding was increase, and caused P available and P potencial were increase too. Plant growth and yield of rice in second season not better than first season, and for intermitten flooding caused better plant growth and yield of rice.    Keyword :  Fe Toxicity, Humic Acid, water management, Recent Ricefiel

SIFAT FISIKOKIMIA LAHAN PERTANIAN MONOKULTUR PADA BEBERAPA KELAS LERENG DI DAERAH UTARA KAKI GUNUNG TALANG

The area at the foot of Mount Talang is one of the areas that excellent in agriculture, especially the cultivation of horticultural crops. In the northern area with steep slope conditions, the local community applies an intensive monoculture cropping system, this will accelerate land degradation in the long term. This study aims to examine the physicochemical properties of monoculture agricultural land in the northern foothills of Mount Talang on several slopes. This research was conducted with a survey method, soil sampling was carried out by means of purposive random sampling, on monoculture agricultural land on slopes > 45%, 25-45%, 15-25%, and 8-15% and forest as control, at a depth of 0 -20cm and 20-40cm. The results showed that the soil texture that dominates at the forest and monoculture agricultural land are dusty loam. Soil water content increases with increasing soil layer depth, soil water content in monocultures 25-45% (73.72%) is the highest. Soil volume weight ranging from 0.4-0.6 g / cm3 has the same tendency at both soil depths. The total pore space of forest land and monoculture agricultural land is a large average of 75% with high criteria. The highest soil organic C content was found in monoculture agricultural land with a slope of >45%. The pH value of H2O for all land uses was 5.15-5.29 and the pH for KCl was 4.5-5.2 for acid criteria. The cation exchange capacity was above 40 me/100g (very high criteria), the total N content was 0.8-1.6% with very high criteria, too. Based on the researchs data, the physicochemical properties of monoculture agricultural land on several slope classes matched the physiochemical conditions of the forest. The potential for land degradation is still minimal even though it is on the upper slopes of the foot of Mount Talang. However, monoculture farming while maintaining soil organic matter content must remain a priority for agricultural land management in this area.Key words: monoculture land, forest, slope, North area of foot Mount Talan

KLASSIFIKASI BAHAN ORGANIK TANAH BUKIT PINANG-PINANG KAWASAN HUTAN HUJAN TROPIK GUNUNG GADUT PADANG

A research about soil organic matter (SOM) classification based on the density was conducted for soil in Bukik Pinang-Pinang region.  The objective of this research was to identify whether the SOM in Pinang-Pinang area, having very high annual rainfall, was mostly particulate or had been associated with mineral particles.  Soils were sampled at three different land use, forest, bush, and mixed wood land on 0-10, 10-20, and 20-30 cm soil depth.  Soil organic matter was classified into 2 classes, < 1.0 g cm-3 and ≥ 1.0 g cm-3 by using pure aquadest.  Total and fractionated SOM samples were analyzed by using Walkley and Black method in soil laboratory, Agriclculture College, Andalas University.  The result showed that, among the three land use surveyed, mixed wood land use gave the highest SOM, then followed by bush land.  Soil OM content in forest ecosystem was much lower than the other two land use for the whole depth.  Based on the density, SOM particulate was higher on the soil surface and decrease by depth in each land use.  Among the ecosystem, SOM under forest was less associated with soil particles than that under bush and mixed wood land. Key Words:  SOM-light fraction, SOM-heavy fraction, land us