PEMANFAATAN BLOTONG DAN SUBSTITUSI AS-UREA
DI KEBUN CIDANGDEUR, PABRIK GULA SUBANG
Isro Ismail, A. Yogasara, S. Simoen, dan M. Mulyadi
ABSTRAK
Penelitian lapangan tentang penggunaan blotong dan substitusi pupuk amonium sulfat (AS) oleh urea pada pertanaman tebu telah dilaksanakan di kebun Cidangdeur, Subang (Typic Dystropept) pada tahun tanam 1993/1994 dan 1994/1995. Penelitian bertujuan untuk mempelajari peluang substitusi pupuk AS-urea yang dikombinasikan dengan penambahan blotong pada tanaman pertama (PC). Perlakuan yang dicobakan meliputi aras pemberian blotong pada PC (B0 = tanpa blotong; B1 = 40 ton blotong/ha) dan tingkat substitusi AS-urea (S1 = 100 % AS; S2 = 75 % AS + 25 % urea; S3 = 50 % AS + 50 % urea; S4 = 25 % AS + 75 % urea; dan S5 = 100 % urea) pada PC dan tanaman keprasan pertama (R1). Kedua faktor tersebut dikombinasikan dalam rancangan petak terbagi (split plot) dengan tiga ulangan. Standar pemupukan N, P, dan K yang digunakan adalah 200 kg N/ha, 90 kg P2O5/ha dan 180 kg K2O/ha. Tebu yang ditanam adalah varietas Ps 58. Blotong hanya diberikan pada PC dan tidak lagi diberikan pada tanaman R1, sedangkan tindakan pemupukan pada R1 sama dengan pemupukan pada PC. Hasil penelitian menunjukkan bahwa pemberian 40 t/ha blotong pada PC serta substitusi AS-urea secara mandiri tidak mempengaruhi bobot tebu, rendemen dan gula pada PC dan R1, namun terdapat pengaruh interaksi antara pemberian blotong dan substitusi AS-urea terhadap bobot tebu dan gula tanaman R1. Pada perlakuan tanpa blotong, substitusi 50 % dan 100 % pupuk AS oleh urea nyata memberikan hasil tebu dan gula tertinggi pada tanaman R1 (masing-masing 1204,7 dan 1151,0 ku/ha serta 84,3 dan 82,2 ku/ha). Pada kondisi ini terbukti bahwa penggunaan urea menghasilkan tebu dan gula nyata lebih baik dibanding penggunaan AS. Penambahan blotong 40 t/ha menghilangkan pengaruh positif substitusi AS-urea tersebut tetapi tidak berpengaruh buruk terhadap bobot tebu, rendemen, dan hasil gula.
Kata kunci: Blotong, Ps 58, bobot tebu, rendemen, gula, Subang
Abstract
A field experiment on filtercake application and the substitution of ammonium sulfate (ZA) by urea had been carried out in Cidangdeur cane field (Typic Dystropept), Subang on the 1993/1994 and 1994/1995 planting seasons. The objective was to evaluate the use of filtercake and the possibility of ZA-urea substitution on sugarcane plantation in that area. Two factors had been tried in this experiment, namely the dosage of filtercake (B0 = without filtercake and B1 = with 40 ton of filtercake/ha), and degree of ZA-urea substitution (S1 = 100 % ZA; S2 = 75 % ZA + 25 % urea; S3 = 50 % ZA + 50 % urea; S4 = 25 % ZA + 75 % urea; dan S5 = 100 % urea). Those two factors were combined in a split plot design with three replications. The dosage of N, P, and K fertilizers were 200 kg N/ha, 90 kg P2O5/ha, and 180 kg K2O/ha respectively. The sugarcane variety used in this research was Ps 58. Filtercake was applied at the first planting (PC) only and the dosage of fertilizer was the same for both PC crops and first ratoon crops (R1). The results showed that both filtercake application and ZA-urea substitution had not any significant effect on the cane weight , sucrose content, and sugar yield of PC and R1 cane. However, there was a significant interaction effect between filtercake application and ZA-urea substitution on cane and sugar yields of R1 cane. In the plots with no addition of filtercake, the substitution of 50 % and 100 % ZA with urea gives the highest yield of cane and sugar (1204.7 and 1151.0 qu cane/ha; and 84.3 and 82.2 qu sugar/ha respectively). It proved that in the study area, urea showed more superior than ZA. Application of 40 t/ha filter cake seems to eliminate the positive effect of ZA-urea substitutions, but have no negative effects on cane yield, sucrose content, and sugar yield. Substitution of 100 % ZA by urea could be suggested in this area because it did not give any negative effect on cane and sugar yield.
Key words : Filtercake, Ps 58, cane weight, sucrose content, sugar, Subang.