Formulation of multi micronutrient fertilizer for mature rubber plantation

Scientific manuring, by adopting balanced nutrition in perennial plantations is the need of hour for increasedproductivity and addressing global warming by adopting 4 R nutrient stewardship. Continuous use of NPKin perennial crops can lead to deficiency of micronutrients. Therefore, a study was carried out to understandnutrient status of major rubber growing tracts and to formulate a customized nutrient mixture for rubber. Adetailed soil fertility assessment and leaf tissue analysis of mature rubber plantations of age group 11-15years in five agro ecological units (AEU) in Thiruvananthapuram were conducted during the study. Based onthis, a multi micronutrient mixture was formulated for rubber and the composition of the mixture was Zn -3.64%, B -8.04 %, Fe- 2.01 %, Cu- 2.55 % and Mn-3.25 %. For accessing the effect of the mixture, a field experimentwas conducted in existing rubber plantation of RRII 105 replanted in 2005 at Aryanad (AEU 14) in randomizedblock design with seven treatments and three replications, namely general recommendation of NPK at 30:30:30kg ha-1year-1, soil test based recommendation of NPK at 22:8:21 kg ha-1year-1, application of multi micronutrientmixture along with soil test based recommendation of NPK at varying levels from 5 to 15 kg ha-1year-1. Thetreatments had a significant effect on dry rubber content (DRC). For the post monsoon, summer, and annualperiod, the highest DRC was noticed in 15 kg ha-1 of the mixture applied plot which was on par with 7.5 kg ha-1 applied plot. Application of micronutrient mixture resulted in enhancement of different micronutrient poolsand enriched nutrient storehouse. It was also observed that available micronutrients were within sufficiencylevel even after application of the mixture. Multi micronutrient mixture application at 7.5 kg ha-1 along with soiltest based recommendation of NPK can be considered for future studies.