The field and laboratory experimental studies were conducted to determine the phosphorus (P) adsorption behavior employing Langmuir Method and yield of sugarcane as affected by compost and inorganic fertilizer applications, and to determine the correlations between the Langmuir parameters and the availability of P in soil or harvested P by the sugarcane. Both field and lab experiments were arranged in a randomized block design, consisting of five treatments (A= 100% NPK, B=100% compost, C=100% NPK + 50% compost, D= 50% NPK + 100%, compost, and E= no fertilizer).  Each treatment was replicated three times. Field and laboratory studies were carried out in the sugarcane field and in the Laboratory of Soil Science, the University of Lampung for Langmuir P studies, respectively. The results showed that the applications of 100% NPK plus 50% organic fertilizer, and 100% NPK resulted in the highest amount of available-P in the soil, the lowest maximum adsorption of P (Xm) and the lowest relative bonding energy of P (km); as well as the highest effect on the increase of sugarcane production. On the other hand, the treatments of no fertilizer and the 100% organic fertilizer resulted in the highest maximum adsorption of P (Xm) and the lowest sugar production. There were very significant negative correlations between the maximum adsorption of P (Xm) and soil P, harvested P by the sugarcane and stem biomass; while similar trend but no significant correlations between the relative bonding energy of P (km) and soil P, harvested P, leaf biomass and stem biomass were detected.

Organonitrofos is one type of organic fertilizer capable of providing macro nutrients that more than other organic fertilizers, particularly nitrogen and phosphorous

Peningkatan produksi tebu banyak terkendala seperti rendahnya bahan organik dan hara makro N, P, K, Ca, dan Mg di tanah ultisol.  Karena di tanah ultisol kandungan kadar Al3+ yang cukup tinggi, dan kejenuhan basa yang rendah.  Penambahan pupuk organonitrofos dan anorganik merupakan salah satu cara untuk mengatasi hal ini.  Penelitian ini bertujuan untuk mengetahui pengaruh kombinasi pupuk organonitrofos dan pupuk NPK terhadap produksi, populasi, dan hara terangkut dan hara terangkut tanaman tebu ratoon 2, dan korelasi antara N-total tanah dan P-tersedia tanah dengan N dan P yang diserap oleh tanaman tebu ratoon 2.  Penelitian ini terdiri  5 perlakuan dan 3 ulangan, disusun dalam Rancangan Acak kelompok (RAK).  Perlakuan terdiri dari: A. 100% NPK (300 kg ha-1 urea, 150 kg ha-1 TSP, 300 kg ha-1 KCl), B. 100% organonitofos (10.000 kg ha-1 organonitrofos), C. 100% NPK + 50% organonitrofos (300 kg ha-1 urea, 150 kg ha-1 TSP, 300 kg ha-1 KCl, 5000 kg ha-1 organonitrofos), D.50% NPK + 100% organonitrofos (150 kg ha-1 urea,  75 kg ha-1 TSP, 150 kg ha-1 KCl, 10.000 kg ha-1 organonitrofos), dan  E. tanpa pemupukan.  Hasil penelitian menunjukkan bahwa Pemberian pupuk anorganik NPK, pupuk organonitrofos dan kombinasi berpengaruh nyata terhadap produksi dan hara terangkut C, N, P tanaman tebu ratoon 2, namun tidak berpengaruh nyata terhadap populasi tanaman tebu ratoon 2. Pemberian 100% NPK, 50% NPK + 100% organonitrofos 100% NPK +50% organonitrofos dan memberikan produksi dan hara terangkut C, N, P tanaman tebu yang tidak berbeda nyata, namun nyata lebih tinggi dibandingkan dengan perlakuan 100% organonitrofos dan tanpa pemupukan. Korelasi positif  N-total tanah dan P-tersedia dengan N dan P yang diserap oleh tanaman tebu ratoon 2, sehingga kandungan N-total tanah dan P-tersedia tanah menentukan jumlah N dan P yang dapat diserap oleh tanaman tebu ratoon 2.