Biochemical Response of Hybrid Maize (Zea mays L.) to NPK Fertilization Based on Spent Bleaching Earth in Field Scale

Indonesia is one of the largest crude palm oil (CPO) producing countries in the world. To improve oil quality, CPO purification is carried out including bleaching earth. The process produced spent bleaching earth (SBE) and deoiled spent bleaching earth (DSBE) classified as hazardous and toxic materials waste. SBE and DSBE have the potential as an adhesive material in the manufacture of NPK fertilizers. This study aimed to compare the effects of SBE and DSBE on replacing clay minerals in terms of biochemical response. The study was arranged in randomized completly block design with three treatments and blocks. The treatment consisted of NPK fertilizer containing 10 brown clay (control), NPK fertilizer containing 5 pure clay minerals + 5 SBE, and NPK fertilizer containing 5 pure clay minerals + 5 DSBE. Data were analyzed using ANOVA and tested using LSD test at a 95 confidence level. The results showed that NPK containing DSBE was able to increase nitrate reductase activity (NRA) (41.9), chlorophyll b content (4.7), glycine betaine (GB) (2.5), decreasing electrolite leakage (19), malondialdehyde (MDA) (23) compared NPK containing brown clay. Thus the use of NPK containing DSBE and NPK containing SBE to be able to replace NPK containing brown clay. © 2020 The Authors, published by EDP Sciences.