MSc

An investigation entitled “Need based nitrogen management in rice (Oryza sativa L.) using diagnostic tools” was carried during the Virippu season (first crop season), 2013 at farmer’s field, Kalliyoor Panchayath, Thiruvananthapuram district, Kerala state. The main objectives of the experiment were to study the technical and economic feasibility of using chlorophyll meter (SPAD meter), leaf colour chart (LCC) and soil testing kit for assessing the crop nitrogen status, to schedule N application in rice based on crop need and to work out the economics.
The field experiment was laid out in Randomised Block Design (RBD) with three replications. The treatments were N application at LCC value 3.0, 4.0 and 5.0, N application at SPAD value 32, 34 and 36, N application based on soil test value using soil testing kit, KAU POP and absolute control.
N application at LCC value 5.0 and N application based on soil test value recorded significantly superior values for plant height, LAI, number of tillers per hill, dry matter production, number of productive tillers/m2, higher straw yield, higher uptake of N, P and K and total chlorophyll of leaves. N application based on soil test value recorded higher gross income.
N application at LCC value 4.0 and SPAD value 36 recorded higher values for grain weight/panicle, filled grains/panicle, thousand grain weight, net income and B:C ratio. Sterility percentage was also minimum for N application at LCC value 4.0, SPAD value 36 and KAU package of practices. N application at SPAD value 36 and LCC value 4.0 recorded significantly higher grain yield, harvest index, agronomic efficiency, physiological efficiency and apparent recovery efficiency. The grain yield with SPAD- 36 and LCC- 4 which received 70 kg N/ha were on par with KAU POP which received 90 kg N/ha in 3 splits. Hence a saving of 20 kg N/ha was achieved with a higher yield compared to POP.
The nutrient status of the soil after the experiment did not show any significant difference except in organic carbon content. The organic carbon recorded was significantly higher under KAU package of practices.
The partial factor productivity and internal utilization efficiency decreased with increase in the total amount of N applied due to higher input cost on fertilizer or less grain yield. The relationship between SPAD values and LCC scores was found to be linear.
It can be concluded from the present study that the rice variety Uma performed best with application of 20 kg N/ha as basal and 25 kg N/ha each applied as top dressing at 40 and 60 DAT (based on LCC-4 or SPAD-36). P and K were applied as per KAU POP. Thus the use of LCC or SPAD meter are efficient tools which helped in reducing the recommended dose of N from 90 kg/ha to 70 kg/ha. Since, the high cost of chlorophyll meter keeps it out of reach of many farmers, the leaf colour chart (LCC) is an inexpensive alternative to the chlorophyll meter. Hence, the LCC based N management is the better option than SPAD based N management practices in farmer’s point of view.