Targeted yield equations of nitrogen for clonal teas under South Indian conditions

Field experiments were conducted for four years from 1997 to 2000 on the tea clones UPASI-9 and S.A-6 to develop targeted yield equations of N and K based on soil test crop response study using correlation and regression analysis. The experiments were conducted in split plot design with N as main plot and K₂O as the subplot treatments each @ 0, 150, 300, and 450 kg ha⁻¹ a⁻¹. The total quantities of N and K fertilizers were given in four split applications avoiding too dry and wet climate conditions. Owing to the failure of various potassium soil test methods to have significant correlation with the yield and nutrient uptake, it had been possible to develop targeted yield equations of nitrogen alone for the Latosols of South India. The statistical analysis carried out on the cumulative made tea yield indicated that the optimum ratio of NK manuring would be 1:1 particularly, when the rate of N is between 300 and 450 kg ha⁻¹. The basic data on per cent contribution of soil (%CS), per cent contribution of fertilizer (%CF) and nitrogen requirement (NR) were calculated and transformed into workable adjustment equations as: (i) FN (UPASI-9) = 118.39 T − 39.41.OC; (ii) FN (SA-6) = 113.97 T − 32.59.OC; where FN is thefertilizer N to be applied in kg ha⁻¹, T is the target in t ha⁻¹ and OC is the soil test value of organic carbon, in per cent. It was found that for a particular yield target at the same level of organic carbon the calculated N dose for UPASI-9 is lower than that of SA-6, which indicates that UPASI-9 is more responsive to N application than SA-6.