Productivity and biological efficiency of sorghum + cowpea in response to row configuration and biofertilizers

Abstract

The study entitled “Productivity and biological efficiency of sorghum + cowpea in response to row configuration and biofertilizers” was undertaken at College of Agriculture, Vellayani, during 2022-2024. The objectives were to assess the performance of sorghum + cowpea intercropping system at varying row configuration, to evaluate the effect of arbuscular mycorrhizal fungi (AMF) and Rhizobium on the competitive behaviour of intercrops and to work out the economics of the system. The field experiment was carried out at the Instructional Farm, Vellayani, from December 2023 to April 2024. The experiment was laid out in randomised block design with 3 x 4 treatments, replicated thrice. The treatments comprised combinations of three row ratios (r1-1:1, r2-1:2, r3- 2:1) and four levels of biofertilizer (b0 – No biofertilizer, b1- AMF, b2 – Rhizobium, b3 – AMF + Rhizobium). The inoculation of AMF and Rhizobium was done for sorghum and cowpea respectively. Sole crops of sorghum and cowpea were raised for computing the intercropping indices. The varieties used for the study were CO-32 (sorghum) and Kanakamony (cowpea). Except nutrient recommendation for sorghum (50:25:75 kg NPK ha-1), all other management practices of both sorghum and cowpea were carried out as per the Kerala Agricultural University Package of Practices (KAU POP) recommendations. Sorghum intercropped with cowpea in 2:1 row ratio (r3) resulted in significantly higher leaf area per plant, dry matter production (DMP), grains per panicle (424.13 nos), grain yield (3122 kg ha-1), and green stover yield (11731 kg ha-1) of sorghum. The treatment b3 (AMF + Rhizobium) resulted in the highest DMP (6270 kg ha-1), grains per panicle (384.49 nos), grain yield (2909 kg ha-1) and green stover yield (11595 kg ha-1) of sorghum. The application of AMF + Rhizobium resulted in a 2.34 per cent higher yield of sorghum than its sole crop. The treatment combination r3b1 (2:1 + AMF) resulted in the highest DMP, grains per panicle and grain yield of sorghum. Rooting depth (13.33 cm) and DMP of cowpea (3254 kg ha-1) were observed to be higher in r3 (2:1 row ratio). Application of Rhizobium alone (b2) resulted in deeper roots in cowpea (11.93 cm). Cowpea raised as intercrop in sorghum in 1:2 ratio along with Rhizobium (r2b2) resulted in more number of nodules per plant (21.93), which was 51.24 per cent more than the sole crop. Significantly higher yield of cowpea (1498 kg ha-1) was observed in r2 (1:2 row ratio). Application of AMF (b1) resulted in higher seed yield (1571 kg ha-1) and haulm yield (2334 kg ha-1) of cowpea. The treatment combination r1b1 (cowpea raised as intercrop in sorghum in 1:1 row ratio along with AMF) exhibited the highest number of pods per plant (9.73) and seeds per pod (10.60) and consequently the highest seed yield (1765 kg ha-1) and haulm yield (2477 kg ha-1) of cowpea. The treatment combination r1b1 recorded 32.5 per cent and 16.56 per cent higher seed yield and haulm yield respectively, when compared to the sole crop of cowpea. At 15 DAS and 30 DAS, the weed density was observed to be lower (7.08 m-2, 14.33 m-2) in r2 (1:2 row ratio). Application of AMF + Rhizobium (b3) resulted in the least weed dry matter at 45 DAS (18.00 g m-2). Sorghum + cowpea at 1:1 row ratio with Rhizobium (r1b2) resulted in lower weed DMP at 15 DAS and 30 DAS. Higher LER (1.93) was observed in the treatment r3b1 (sorghum intercropped with cowpea in 2:1 ratio along with AMF). Aggressivity values of cowpea in combination with sorghum were positive irrespective of biofertilizer application. Competition index (-0.05), sorghum equivalent yield (6411 kg ha-1) and percentage yield difference (117.93 %) were higher in r1b1 (sorghum intercropped with cowpea in 1:1 row ratio along with AMF). The competition ratio was observed to be higher (0.91) in r2b3 (1:2 ratio along with AMF and rhizobium) for sorghum and r1b0 (1:1 ratio without biofertilizer) for cowpea (2.82). The NPK uptake of sorghum + cowpea system (133.33 kg ha-1, 24.88 kg ha-1 and 92.08 kg ha-1) were observed to be higher in r3 (2:1 row ratio). While AMF application (b1) resulted in significantly higher N and P uptake, AMF + Rhizobium showed higher K uptake. The crude protein in sorghum grains and cowpea seeds was higher (10.16 %, 23.33 %) in r2b1 and r3b2 respectively. Iron and copper content in sorghum grains were observed to be higher with the application of AMF (b1) (5.29 mg 100 g-1 and 0.33 mg 100 g-1) Application of Rhizobium (b2) resulted in higher manganese content in sorghum grains (1.77 mg 100 g-1).While the calcium content in sorghum grains was higher in r2b1 (1:2 + AMF), the content of manganese was noted to be higher in r1b2 (1:1 + Rhizobium). . Post-experiment soil analysis revealed higher organic carbon, electrical conductivity and available P in r1b2. The available N and K status were observed to be higher in r3b1 (246.33 kg ha-1) and r2b1 (275.20 kg ha-1) respectively. The soil pH was observed to be higher (5.77) in r2b0, which was 0.31 units higher than the initial pH (5.46). Sorghum + cowpea in 1:1 ratio along with AMF (r1b1) resulted in higher net income (₹126922 ha-1) and monetary equivalent ratio (MER) (2.06). However, benefit cost ratio was observed to be higher (2.00) in r3b0 (sorghum + cowpea in 2:1 row ratio without biofertilizer) and r3b1 (sorghum + cowpea in 2:1 row ratio along with AMF). From the experiment it was concluded that compared to the respective sole crops, sorghum + cowpea intercropping system excelled in terms of overall productivity and biological efficiency. In terms of land equivalent ratio, sorghum + cowpea (2:1) along with AMF (r3b1) was more productive. However, considering the sorghum equivalent yield, percentage yield difference, net income and monetary equivalent ratio, intercropping sorghum with cowpea in 1:1 row ratio along with arbuscular mycorrhizal fungi could be recommended as a viable combination for higher productivity and profitability.