Soil CO2 and N2O Emissions Affected by Ameliorant Types and NPK Fertilizer Rates under Chili Cultivation on Peatlands

ABSTRACT The use of peatlands for agriculture often causes controversy on Indonesia and allegedly increases greenhouse gas emissions caused by fertilization. Ameliorants are often used on peatland to increase productivity. The effects of ameliorant on GHG emissions depends on the characteristics of ameliorants. Determination of the type of ameliorant and the appropriate rate of NPK fertilizer is needed to mitigate CO2 and N2O emissions for red chili cultivation on peatland. This research was carried out on peatland in the village of Kalampangan, Sebangau District, Kodya Palangkaraya, Indonesia from June to October 2017. The treatments given were: Factor I; the types of ameliorant material (A1;100% cow manure, A2; 50% cow manure + 50% biochar A3; 50% cow manure + 50% compost from weed in situ; A4; 50% cow manure + 50% ash from weeds in situ), Factor II; the rate of NPK fertilizer (D0; No NPK, D1; 50% of recommended dose; D2; 100% of recommended dose, D3; 150% recommended dose). The treatments were arranged in a factorial randomized block design (RBD), with three replications. Recommended rates of urea (N), SP-36 (P2O5), and KCl (K2O) were 100-200-120 kg/ha. Observation variables include soil pH, soil Eh, water contents, soil CO2 and N2O emissions were measured using closed chamber at the vegetative phase (1st month), the initial generative phase (2nd month), and the end of generative phase (3rd month), meanwhile the ground water level was measured using a Micro-GC gas chromatography (GC) every week during the course of this research. The results showed that CO2 emission were more influenced by the type of ameliorant than the fertilizer dose, while N2O emission was more influenced by NPK fertilizer rates. The lowest CO2 emission was observed from the application of 50% cow manure + 50% compost from weed in situ, which could reduce CO2 emissions up to 40% (1709 kg/ha/season) of the control treatment (100% cow manure) (3731 kg/ha/season). The highest N2O emissions were shown by ameliorant A3 (50% cow manure + 50% compost from weed in situ) at dosage NPK 150% from recommendation (1,31kg/ha/season) and the lowest shown by ameliorant A4 (50% cow manure + 50% ash from weeds in situ) at no NPK fertilization (0.32 kg/ha/season). The recommended treatment is the treatment of ameliorant 50% cow manure + 50% compost from weed in situ at 100% NPK rate