MSc

The project “Evaluation of micronutrient formulation in cowpea (Vigna unguiculata L. Walp)” was carried out at College of Agriculture, Padannakkad and Regional Agricultural Research Station (RARS), Pilicode during 2017 to 2019. The objectives of the study were to evaluate the effect of micronutrient formulation through seed treatment and foliar nutrition on growth, nodulation and yield of cowpea and to study its effect on plant nutrient uptake and residual soil nutrient status.
Laboratory study was carried out at COA, Padannakkad to formulate and standardize the micronutrient solution for cowpea. Different concentrations of the standardized micronutrient formulation were used for seed treatment study (Experiment 1). The experiment was carried out in completely randomized design with 7 treatments and 3 replications which included seed treatment with micronutrient formulation @ 0.25, 0.50, 0.75, 1, 1.5 and 2 per cent as T1, T2, T3, T4, T5 and T6 respectively. T7 (seed treatment with water) was the control. Observations on germination percentage, number of days taken for germination, seedling length at three leaf stage and seedling vigour index were recorded. Treatment T6 (micronutrient formulation @ 2 %) showed highest seedling length (24.23 cm) and seedling vigour index (2423) which was followed by T5 (micronutrient formulation @ 1.5 %). Thus the best and second best treatment from seed treatment study was concluded as T6 and T5 respectively and was selected for the field experiment (Experiment 2).
The field experiment was conducted in randomized block design with 12 treatments replicated three times. The treatment consisting of combination of four levels of seed treatment (no seed treatment, seed treatment with rhizobium, seed treatment with best concentration from experiment 1 and second best seed treatment from experiment 1) and three levels of foliar application of micronutrient (no foliar application, one foliar application at 15 DAS and two foliar applications at 15 and 30 DAS). Biometric observations were recorded at flower bud initiation and at harvest.
Plant height at flower bud initiation and at harvest was superior in S3 (Seed treatment with micronutrient formulation at 2 %) while stem diameter was highest in S4 (seed treatment at 1.5 %) and S3 respectively in both stages. Double foliar spray was superior in plant height and stem diameter at both stages. Interaction S3F3 (2 per cent seed treatment plus two foliar spray) recorded highest plant height at both stages and stem diameter was highest in S2F3 (treatment with rhizobium plus two foliar spray). Number of nodules was highest in S2 (seed treatment with rhizobium). Number of pods per plant (21.02 & 20.97), pod weight per plant (36.14 g & 33.49 g), grain yield (2224 kg ha-1) and dry matter production (2292.91 & 2372.92 kg ha-1) was superior in S3 and F3 (two foliar spray). Interaction S3F3 was superior in number of pods per plant (25), pod weight per plant (38.11 g), grain yield (2320 kg ha-1) and dry matter production (2613.24 kg ha-1).
Leaf analysis revealed that P and K content in leaf was highest in S3. N, P, K and Ca content in leaf was highest in F3. Interaction S3F3 recorded highest N, P and K content in cowpea leaf. Mg content was highest in S2F3 (treatment with rhizobium plus two sprays). Fe, Mn, Zn and B content in leaf was highest in S3 and F3. Interaction S3F3 (2 per cent seed treatment plus two foliar spray) recorded highest Fe, Mn and Zn content in cowpea leaves. The uptake of N, P, K, Ca, S, Fe, Mn, Zn and B were highest in both S3 and F3 whereas Mg uptake was highest in S3 and F2 (one foliar spray). Cu uptake was highest in F3. Interaction S3F3 recorded highest uptake of N, P, Mn and Zn. N content in cowpea grain was superior in S2 and F3. While K, Ca, Fe, Mn, Zn, Cu and B content in cowpea grain was highest in both S3, F3 and interaction S3F3. In case of interaction, N was highest in S2F3. The uptake of N, P, K, Ca, Mg, S, Fe, Zn and B in cowpea grain was highest in both treatments S3 and F3 and the interaction, S3F3 recorded highest uptake of P, K, Ca, Fe, Mn, Zn and B in grain.
Studies on residual soil nutrient status revealed that available N and P in soil was highest in S2 at both 45 DAS and at harvest. Available K was highest in S3, F3 and S3F3 at both stages. Organic carbon content was found to increase in plots receiving two foliar spray and interaction S3F3. Available Fe, Mn and Zn was highest in S3 at harvest and in F3 at both stages. Available B was highest in S3 and F3 at 45 DAS while Mo at harvest. B and Zn were highest in S3F3 at 45 DAS while at harvest available Fe was found to be higher in S3F3. Available Fe at 45 DAS was highest in S1F3 (no seed treatment plus two foliar spray). Root CEC was superior in S3, F3 and in interaction S3F3.
The results obtained from the investigation revealed that the application of micronutrient formulation as two foliar spray (15 and 30 DAS) along with seed treatment (2 per cent) was found to be highly effective in increasing the growth and yield characters of cowpea. The uptake of nutrients in cowpea leaf and grain was also found to increase with the application of micronutrient formulation enhancing the nutritional quality of grain.