Phosphorous and boron interactions in black cotton soils of kerala with respect to groundnut (Arachis Hypogaea L.)

Abstract

Balanced supply of nutrients is one of the most important factors determining crop yield. Sometimes the applied nutrients may not be available for plant use, as their availability depends on interaction between nutrients. When the supply of one nutrient element affects the absorption and utilization of other nutrient element, the elements are said to be in interaction and interactions may be negative or positive. In Kerala, black cotton soils are seen in Chittur taluk of Palakkad district occupying an area of approximately 2000 ha. These soils are sandy clay loam, dark, calcareous, neutral to alkaline (pH 7.0 to 8.5), high in clay content and CEC. These soils are sufficient in all nutrients except phosphorus (P) and boron (B). Finding the interaction between Band P in black soils will help to understand the factors determining the availability of these nutrients to crops. The present study was carried out in College of Horticulture, Vellanikkara during 2016-18. The objectives of the study were to find out the interactions of boron and phosphorus in black cotton soils of Palakkad and to assess the treatment level of boron (B) and phosphorus (P) for maximizing the yield. The study consisted of a field experiment with groundnut variety, K-6 in black cotton soils of Chittur, Palakkad followed by analysis of soil, plant and pod samples taken from the experimental field. Soil samples were collected from different locations of Chittur and analyzed for available P and B. Field experiment was carried out where deficiency of both P and B was noticed. Experiment was laid out in factorial RBD with 17 treatments and 4 replications. Treatment combinations were made with four levels of P and four levels of B with soil test based recommendations as control. N and K levels are kept same (based on POP recommendations of KAU) for all treatments except for the first treatment where soil test based recommendations was given. P0 - 0 kg ha-1, P1 - 60 kg ha-1, P2 -75 kg ha-1 and P3 -90 kg ha-1 were the four levels of P and B0 - 0 kg ha-1, B1 - 5 kg ha-1, B2 - 10 kg ha-1 and B3- 15 kg ha-1 were the four levels of borax. super phosphate (SSP) was used as source of P and borax was used as source of B. Physical characteristics of soil viz., texture and bulk density were analyzed before experiment and chemical characteristics viz., pH, EC, organic carbon, N, P, K, Ca, Mg, S, Fe, Mn, Zn, Cu and B were analyzed before and after the experiment. parameters like plant height and number of leaves per plant were recorded at flowering, pegging, pod setting and harvest stages and yield parameters like number of pods per plant and yield were recorded at harvest stage. Plant nutrient content was analyzed and uptake was computed at different stages viz., flowering, pegging, pod setting and harvest stages whereas pod nutrient content and uptake was computed only at harvest stage. Soil nutrient status, plant nutrient content and uptake of nutrients were affected by main effect and interaction effect of P and B. Application of P at 90 kg ha-1 and B at 0 kg ha-1 resulted in highest plant height and number of leaves per plant. Application of P at 90 kg ha-1 and B at 5 kg ha-1 resulted in highest number of pods per plant and yield. Application of P at 90 kg ha-1 and B 0 kg ha-1 resulted in highest protein content in groundnut. Application of increased dose of P reduced availability of B due to anionic competition. Application of P reduced the availability of Fe, Mn and Zn in soil due to the formation of insoluble compounds like Fe-P, Mn-P and Zn-P. Application of P enhanced the availability of N. K content in soil was reduced with increased dose of P application. Ca and S were increased due to its supply through fertilizer in soil. Plant nutrient content showed a decreasing trend from flowering to harvest stage. Application of P enhanced plant and pod P content and application of B reduced plant and pod P content. Content of N, P, K, Ca and S was increased with increased levels of P and content of Fe, Mn, Zn and B was reduced with increased dose of P. Content of N, P, S, Zn and B were higher in pod than plant. Uptake of nutrient followed an increasing trend from flowering to harvest due to increased dry matter production. The uptake of N, P, S, Zn and B by pod was higher compared to plant uptake.