CH4 and N2O Emissions and Productivity of Physic nut (Jatropha curcas L.) In Three Nitrogen Fertilizer Sources.

Abstract

Methane (CH4) and nitrous oxide (N2O) are important atmospheric trace gases influencing radiative forcing and atmospheric chemistry. Agriculture is one of the anthropogenic sources of CH4 and N2O. Physic nut (Jatropha curcas L.) is a kind of plant than can be used as plant oil sources. Application of nitrogen fertilizer can increase plant growing including physic nut. The effect of nitrogen addition through fertilization on greenhouse gases (CH4 and N2O) in physic nut cultivation area is poorly understood. Therefore, the aim of this study was to investigate effects of nitrogen fertilization on CH4 and N2O emissions and grow of physic nut. For this purposes, 13 treatments of nitrogen fertilizer was applied including surface application of urea 50%, surface application of urea 100%, deep placement of urea 50%, deep placement of urea 100%, surface application of jatropha cake 50%, surface application of jatropha cake 100%, deep placement of jatropha cake 50%, deep placement of jatropha cake 100%, surface application of slow release urea 50%, surface application of slow release urea 100%, deep placement of slow release urea 50%, deep placement of slow release urea 100% and control. Application of 100 % fertilizer was 80 g for urea and slow release urea, and 2 kg of jatropha cake. This experiment was arranged in Completely Random Block Design in three repetitions. The result of the experiment showed that deep placement of jatropha cake 100% gave the best result in plant height and number of leaf. Surface application of urea 100% gave the best result on physic nut productivity. Surface application of urea 100% produced 28.56 numbers of fruits, more than the other treatments, but this treatment was not significant different to deep placement of jatropha cake 100%. From diurnal change analysis, we determined the best time to take gas emission, that is between 07.00-09.00 a.m. CH4 emission had significant correlation with NH4 + concentration (p: 0.0487; r: 0.556). CH4 emission was not have correlation with pH, Eh, soil moisture, and soil nitrate. Increasing N concentration could affect N2O emission. N2O emission was not influenced by pH, soil moisture, and Eh. Measurement of soil variable in different soil depth showed that pH value had significant correlation with Eh (p<0.0001; r ; -0.840). Whereas, NH4 + and NO3 - were not different in various soil depths because soil depth that measured is still rhizosphere area of physic nut root. The deep placement of jatropha cake 100% treatment gave the best result in carbon stock analysis. Carbon stock of physic nut by this treatment reached 11.159 ton C/ha/year. Urea deep placement 100% gave the highest output energy value of 134 675 MJ/ha along 5 months.

Metana (CH4) dan dinitro oksida (N2O) adalah adalah gas penting di atmosfer yang mempengaruhi kekuatan radiasi dan sifat kimia atmosfer. Pertanian adalah salah satu kegiatan manusia yang menjadi sumber emisi CH4 dan N2O. Tanaman jarak pagar (Jatropha curcas L.) adalah salah satu jenis tanaman yang dapat digunakan sebagai sumber minyak nabati. Peenggunaan pupuk nitrogen telah diketahui mampu meningkatkan pertumbuhan tanaman termasuk diantaranya tanaman jarak pagar. Acuan rekomendasi pemupukan telah diketahui. Namun, bagaimana perannya dalam menghasilkan emisi gas rumah kaca belum diketahui. Pengaturan pemupukan yang baik diharapkan dapat mereduksi emisi gas rumah kaca dan meningkatkan serapan karbon tanaman. Bertolak dari hal tersebut, penelitian ini bertujuan untuk mengetahui pengaruh pemberian pupuk nitrogen terhadap emisi CH4 dan N2O dan pertumbuhan tanaman jarak pagar.