Prameela, PVandana, G PaiKAU2023-02-152023-02-152020175091https://krishikosh.egranth.ac.in/handle/1/5810193841PhDAn experiment entitled “Nutrients and tillage interactions in rice fallow cowpea production” was conducted during 2017-2019 at College of Horticulture, Vellanikkara of Kerala Agricultural University, Thrissur. The study consisted of two experiments. Experiment-1 was a pot culture study undertaken during 2017, to find out optimum dose of potassium and magnesium sulphate for cowpea. The experiment was laid out in CRD with 14 treatments and three replications. The treatments included three levels of K2O (10, 20 and 40 kg/ha), and four levels of MgSO4 (40, 60, 80 and 100 kg/ha). Apart from K: MgSO4 @ 10:80 kg/ha (KAU package of practices) and soil test based nutrition (K: MgSO4 @12:80 kg/ha) were also included. Nitrogen and P2O5 were applied at the rate of 20 and 30 kg/ha, respectively, uniformly to all pots. A bush type variety of cowpea Anaswara released from Kerala Agricultural University was used in the study. In the pot culture experiment, application of K2O: MgSO4 @ 40: 40 kg/ha and 40:100 kg/ha resulted in taller plants. At 60 DAS, POP based nutrient application registered more number of branches (12.7 /plant), which was on par with K2O: MgSO4 @ 10:60 (T2), 20:40 (T5), 20:100 (T8), 40:40 (T9), 40:80 (T11), 40:100 (T12) kg/ha as well as to soil test based nutrition (T14). Highest number of root nodules (201) and higher dry matter production at harvest (44 g/plant) was observed in application of K: MgSO4 @ 40:100 kg/ha (T12). An increase in dry matter production of cowpea was observed with magnesium sulphate nutrition. Various levels of K and Mg resulted in significant variation in chlorophyll a and total chlorophyll content. Application of potassium and MgSO4 @ 40:60 kg/ha resulted in higher number of pods and grain yield (40.3 g/plant) and it was statistically comparable to T11 and T12 (K2O: MgSO4 @ 40:80 & 40:100 kg/ha). Based on grain yield, treatments K: MgSO4 @ 20:60 kg/ha, 20:80 kg/ha, 40:60 kg/ha, 40:80 kg/ha were selected for field trial along with soil test based nutrition as control. The second experiment aimed at assessing the effect of various tillage practices, and varied doses of potassium and MgSO4 on growth and yield of cowpea and to work out economic viability. Field experiments were undertaken in rice fallow during 2017 and 2018 (November/December - March/April). Soil of the filed was high in organic carbon, available N, but deficient in available P, K, and Mg. The experiment was laid out in RBD and the treatments were factorial combinations of three types of tillage and varied doses of potassium and magnesium sulphate and it was replicated thrice. Zero tillage (ZT- M1), minimum tillage (MT- M2) and conventional tillage (CT- M3) were the major factors and five nutrient doses (S1-S5) were soil test based nutrition (S1- 11-13 kg K2O/ha along with 80 kg MgSO4/ha), 20 kg K2O/ha along with 60 kg/ 80 kg MgSO4/ha (S2 & S3) and 40 kg K2O/ha along with 60 kg/ 80 kg MgSO4/ha (S4 & S5). N and P2O5 were applied at the rate of 20 kg/ha and 30 kg/ha in all plots. Seeds were dibbled at spacing of 30 cm x 15 cm. In zero tillage, herbicide glyphosate was sprayed @ 0.85 kg/ha two weeks before sowing. In minimum tillage, strip tillage using spade was adopted at a spacing of 30 cm. In conventional tillage, land was ploughed twice followed by formation of small ridges and furrows at a spacing of 30 cm. The plot size was 6 m x 4.2 m. Germination percentage of cowpea (at 7 DAS) was significantly higher in conventional tillage (79 %), whereas, it was very low in zero till (44 %) and intermediate in MT (58 %). Tillage systems and potassium, magnesium sulphate doses had no significant effect on plant height of cowpea, and at 60 DAS average height was 47.5 cm, 52.9 cm and 48.4 cm under zero tillage, minimum tillage and conventional tillage, respectively. At 45 DAS and 60 DAS minimum tillage resulted in higher number of branches per plant whereas, plants in conventional tillage showed earliness in 50 % flowering. Significantly higher LAI was recorded in zero tillage, followed by minimum and conventional tillage. Application of K: MgSO4 @ 40:80 kg/ha also resulted in higher LAI. Zero tillage along with K: MgSO4 @ 40:80 kg/ha (M1S5) recorded the highest LAI. Tillage had no significant effect on chlorophyll a, chlorophyll b, and total chlorophyll content and on chlorophyll a/b ratio. Whereas, potassium and magnesium sulphate application had significant effect on chlorophyll content. Application of K: MgSO4 @ 20:60 kg/ha and K: MgSO4 @ 40:80 kg/ha resulted in higher as well as comparable chlorophyll a and total chlorophyll content. Among interactions ZT with K: MgSO4 @ 12:80 kg/ha (soil test) and CT along with K: MgSO4 @ 20:60 kg/ha higher chlorophyll a content. Dry matter production at early growth stage was higher under conventional tillage, followed by minimum tillage and zero tillage. Whereas, at 75 DAS, highest dry matter was registered under minimum tillage (3240 kg/ha). However, at 90 DAS, both minimum and conventional tillage resulted in higher as well as comparable dry matter (2043 kg/ha and 2085 kg/ha). Root length and root spread were higher under zero tillage followed by MT and CT. Application of K: MgSO4 @ 40:60 kg/ha also resulted in higher root spread. Zero tillage with K: MgSO4 @ 40:60 kg/ha (45.2 cm) resulted in longest roots and higher root spread (2695 cm2). Conventional tillage along with supply of K and MgSO4@ 40 and 80 kg /ha registered shortest roots and lower root spread. Pooled analysis showed that, among various tillage systems, significantly higher grain yield was realized under minimum tillage (735 kg/ha). This was followed by conventional tillage (648 kg/ha) and zero tillage (618 kg/ha) which were on par. Among varied potassium and magnesium doses, application of K: MgSO4 @ 40:60 kg/ha was found to be the best (grain yield of 806 kg/ha). Hence combination of minimum tillage along with K: MgSO4 @ 40:60 kg/ha resulted in the highest grain yield (915 kg/ha). Uptake of nutrients at 30 DAS followed the order of CT>MT>ZT. At harvest, higher uptake of potassium, and magnesium was noted in K: MgSO4 @ 40:60 kg/ha under minimum tillage. There was no significant variation with respect to grain protein content of cowpea due to various tillage practices whereas higher content was registered with application of K: MgSO4 @ 40:80 kg/ha (26.2 %).EnglishThesis