Input optimization for short duration Red gram [Cajanus cajan (L.) Millsp.]

Abstract

The study entitled “Input optimization for short duration red gram [Cajanus cajan (L.) Millsp.]” was conducted at College of Agriculture, Vellayani during 2017 - 2020 with the objectives, to assess the suitability of two short duration varieties of red gram, standardize the spacing and nutrient management practices for short duration red gram and to examine the legume effect on succeeding fodder maize crop. The investigation was done as three experiments (i) assessment of the suitability of two short duration varieties and standardization of spacing and nutrient levels (ii) assessment of legume effect on fodder maize and (iii) nutrient scheduling in red gram. The experiment I was laid out in randomized block design (RBD) with three replications during Rabi season (November to March) in 2018 - 2019 and the confirmatory experiment, during 2019 - 2020. The treatments included combinations of varieties [v1: APK 1; v2: Vamban (Rg) 3], spacings [s1: 40 cm x 20 cm; s2: 60 cm x 30 cm] and nutrient levels [ n1: 40:80:40, n2: 30:60:30; n3: 20:40:20 kg NPK ha-1 ]. Half nitrogen (N), potassium (K) and full phosphorus (P) were given basally, remaining as top dressing, 30 days after sowing (DAS). Farmyard manure (FYM) was applied uniformly @ 12. 5 t ha-1 . The varieties, spacings and nutrient levels had significant influence on the growth characters of red gram at the different stages of observation. Variety Vamban (Rg) 3 (v2) recorded significantly taller plants, higher number of branches and root parameters compared to APK1 (v1) during both the years of experimentation. The wider spacing, s2 (60 cm x 30 cm), the highest nutrient level, n1 (40:80:40 kg NPK ha-1 ) and the combination, v2s2n1 resulted in superior values for plant height, number of branches per plant, root volume and root dry weight, while narrow spacing (40 cm x 20 cm) recorded the highest number and weight of nodules per plant. The interactions also exerted significant influence on growth parameters with the interactions involving v2, s2 and n1 recording higher values. The variety APK 1 showed earliness in flowering with significantly higher average pod weight, 100 seed weight, seed yield (1.04 t ha-1 ) and haulm yield (3.70 t ha-1 ). Narrow spacing and the highest nutrient level recorded superior values for average pod weight, seed and haulm yields. The interactions also resulted in significant variations in yield attributes and yield. Pooled analysis of yield data of the two years registered the highest seed yield (1.38 t ha-1 ) in v1s1n1 (APK 1 + 40 cm x 20 cm + 40:80:40 kg NPK ha-1 ). Maximum dry matter production (DMP), crop growth rate (CGR) and seed protein content were recorded in APK 1 and at the highest nutrient level. Among the spacings tried, wider spacing resulted in the highest DMP and seed protein, while CGR was higher in the narrow spacing. The partial factor productivity (PFP) for N, P and K were superior in the combination v1s1n1 in both years. Individual effects of the variety APK 1, narrow spacing and the highest nutrient level recorded maximum nutrient uptake and in the combinations of APK 1 or Vamban (Rg) 3 with 40 cm x 20 cm and 40:80:40 kg NPK ha-1 . Available soil N and microbial counts assessed after the experiment were the highest after APK 1. Wider spacing and the highest NPK level recorded maximum soil available nutrient status, while microbial counts, at narrow spacing. Soil nutrient balance sheet computed for N was positive during both years. The balance sheet for P was positive for all the treatment combinations involving wider spacing during the first year. During the second year, all treatments showed positive balance for P except v1s1n1, v1s1n2, v1s2n2 and v2s2n3. Nutrient balance for K was positive in treatments v1s1n1, v1s2n1 and v2s1n1 during the both years. Pooled mean of the economics of cultivation during the two years revealed maximum net returns per hectare (₹ 88621/-) and B:C ratio (2.03) in v1s1n1 (APK 1 + 40 cm x 20 cm + 40:80:40 kg NPK ha-1 ). The legume effect of red gram on fodder maize was assessed during Kharif season, June to August 2019. Crop residues (root + shoot + fallen leaves) of red gram were incorporated in situ and allowed to decompose for two months. The maximum quantity of residues (4.83 tha-1 ) was generated in the treatment combination T7, Vamban (Rg) 3 + 40 cm x 20 cm + 40:80:40 kg NPK ha-1 imposed in red gram, which was on par with T1, the combination, APK 1 + 40 cm x 20 cm + 40:80:40 kg NPK ha-1 (4.75 tha-1 ). There were no marked variations in the biochemical characters of residues, while C: N ratio was significantly narrower in T1 (18.2: 1) and T7 (18.9:1). Residue incorporation improved the soil chemical properties and at 60 days after residue incorporation (DAI), maximum soil pH and C pool (total organic carbon and labile carbon) were estimated in treatment T7, and recalcitrant organic carbon, in T1. Soil available N, P status and dehydrogenase activity were higher in T1, and available K, in T7 at 60DAI. Fodder maize seeds (variety, African tall) were sown during the third week of June in the residue incorporated plots. Green and dry fodder yields (33.61 and 11.37 t ha-1 respectively) were the highest in the treatment T7 which was on par with T1 (32.85 and 11.08 t ha-1 respectively). Soil available NPK status were found to decline from the initial status with fodder maize cultivation. The nutrient scheduling experiment was conducted during Rabi season, 2019 - 2020, in RBD with nine treatments and three replications. The variety APK 1, spacing 40 cm x 20 cm and nutrient level 40:80:40 kg NPK ha-1 found superior in Experiment I were adopted. The integrated nutrient management (INM) practices evaluated were T1: 100 % NPK as chemical fertilizers, T2: 100 % N + 50 % P + 100 % K + P solubiliser, T3: 100 % N + 100 % P + 50 % K + K solubiliser, T4: 100 % N + 50 % P + 50 % K + P solubiliser + K solubiliser, T5: T1 (50 % N foliar), T6: T2 (50 % N foliar), T7 : T3 (50 % N foliar), T8 : T4 (50 % N foliar) and T9 : Absolute control: No fertilizers. The entire dose of N was given as soil application in T1 to T4 and foliar spray of 50 per cent N in T5 to T8 with urea (2 %) at 30 and 45 DAS. Phosphorus and K solubilisers (Bacillus megaterium and Bacillus sporothermodurans respectively) were mixed with powdered FYM in the ratio 1: 50 separately, and 10 g of each mixture was added in soil one week after basal fertilizer application. The INM practice of 100 per cent N + 50 per cent P + 50 per cent K along with P and K solubilisers (T4) recorded significantly taller plants (109.70 cm), maximum number of branches (6.5) at harvest, whereas weight of nodules per plant at flowering (0.59 g) and root parameters were significantly the highest in treatment T8. Average pod weight (0.62 g) and seed yield (1.48 t ha-1 ) were superior in T4 and on par with the combination involving foliar nutrition, T8 (1.46 t ha-1 ). Integration of P and K solubilisers with chemical fertilizers (100 % N and 50 % P and K), registered 50 per cent higher yield than the absolute control. Among the agronomic indices, DMP at 100 DAS (34.18 g plant-1 ), CGR at 80 - 100 DAS (3.44 g m-2 day-1 ) were the highest in T4, and RGR, in T2 followed by T4. Substitution of 50 per cent Pand K with biofertilizers recorded maximum uptake of N, P and K and physiological efficiencies for the nutrients. Computation of nutrient balances with the INM practices adopted revealed the highest positive balance for N in T8, P in T4 and for K in T7. Economic analysis showed the treatment T to record the highest net return per hectare (₹ 94722 /-) and B: C ratio (2.05). Based on the results it could be concluded that the short duration red gram varieties, APK 1 and Vamban (Rg) 3 are suitable for cultivation in the southern laterites of Kerala. The variety APK 1 was superior in terms of yield and profit and can be recommended for planting at a spacing of 40 cm x 20 cm and an NPK dose of 40:80:40 kg ha-1 based on the soil test results. Evaluation of the legume effect of red gram revealed significant increases in soil fertility status with residue incorporation. Among the treatments imposed in red gram, irrespective of the variety, the residual effect realized with red gram planted at 40 cm x 20 cm spacing and fertilized with 40:80:40 kg NPK ha-1 was found to be superior in terms of fodder yield in the succeeding crop of maize. The integrated nutrient management practice that proved profitable in APK 1 involved application of 40:40:20 kg NPK ha-1 as chemical fertilizers along with P and K solubilisers, the entire dose in soil.