Produksi biomassa oleh tanaman rumput gajah, koro benguk, kaliandra dan flemingia di lahan bekas penambangan pasir besi Kecamatan Kutoarjo, Purworejo Jawa Tengah

Abstract

Iron sand as one type of mineral is a great potency in the subdistrict of Kutoarjo, Purworejo district. However, it has been realized that mining activities can not be separated from the effects towards the surroundings environment, especially from the aspect of land degradation. Physically, the land at the site of the iron sand post mining is dominated by the sandy texture. One method of amelioration for sandy soils is by providing organic material. In this research, the organic material was supplied in situ from the elephant grass (Pennisetum purpureum Schumach), velvet bean (Mucuna pruriens), red calliandra (Calliandra calothy rsus ) and winged-slack flemingia (Flemingia congesta). The objectives of this research were to know the amount of biomass produced by each plant type and to find out the quality of plant biomass based on N, P, K absorption parameters in plants. The plants which had to be tested on each plot were: (1) elephant grass, (2) velvet bean, (3) a combination of elephant grass and winged-slack flemingia, (4) a combination of elephant grass and red calliandra, (5) a combination of velvet bean and winged-slack flemingia, and (6) a combination of velvet bean and red calliandra. Each treatment was tested in experimental plots measuring 240 m2 and were repeated three times, so there were 18 experimental plots, plus three control plots measuring 100 m2. Overall the research area was reaching 4620 m2. The results from over five months research showed that the biomass of plants with the largest amount was produced by elephant grass at the fourth plant treatment plot and also by velvet bean at the fifth plant treatment plot. The elephant grass at the fourth plot capable of producing dry matter 8.32 tons/ha in 18 weeks, while the velvet bean at the fifth plot produce dry matter 2.13 tons/ha in 18 weeks. Both of these plants had a relatively more balanced ratio of N, P and K contents and uptakes in plants. The NPK ratio of fourth plot was (0.79:0.13:1.47) and the fifth plot was (1.74:0.15:0.76). Plants that produce high biomass can provide a large amount of organic material in the post mining land which lack of organic material. In addition, the content and balanced nutrients uptake in plant biomass play a role in improving the availability of nutrients in the land.