LEAF CHLOROPHYLL METER- A NON-DESTRUCTIVE METHOD FOR SCHEDULING NITROGEN IN POTATO CROP

Abstract

A leaf chlorophyll meter (SPAD 502) was used as a tool for N-fertilization in potato. SPAD value of an over
fertilized plot was used as reference to application of subsequent split doses after earthing up in different treatment plots
for two prevalent varieties Kufri Jyoti and Kufri Chandramukhi. In different treatments the SPAD values differed for
two varieties. Among different treatments (N schedules) higher SPAD value was observed throughout in over fertilized
reference plots where 125% of recommended N was applied. In tuber yield, Kufri Jyoti (36.7 t/ha) was higher than Kufri
Chandramukhi (30.5 t/ha) at all N levels/treatments. Total tuber yield under different N doses ranged from 33.1(Kufri
Chandramukhi) to 34.8 (Kufri Jyoti) t/ha. Among various N schedules and levels there was no significant difference in
tuber yield, though, the highest yield was obtained in the treatment where 10% of recommended N was applied at 95%
of reference SPAD after basal (50%) and earthing up (20%) applications followed by in over fertilized plot there by
saving 20% of recommended N (36 kg/ha). This indicated that increasing the number of splits of N supplied N to the
crop for longer duration to maintain the yield level of both varieties compared to over fertilized plot even at much lower
N application rate. The best period to detect N deficiency in potato for corrective N fertilization was found to be on or
before 45 DAP which is tuberization phase. Gross return (2.26 lakh/ha), net return (1.53 lakh/ha) and B:C ratio (3.1) was
higher with Kufri Jyoti compared to Kufri Chandramukhi. Among different N treatments gross return (2.09 thousand /
ha), net return (1.37 thousand/ha) and B : C (2.9) ratio were highest with 50% at planting + 20% at earthing + 10% at 95%
reference value. Thus, there was 20% saving of N by splitting of N based on SPAD value.