Nutrient interactions in soil test crop response studies on cucumber ( Cucumis sativus L) in the laterite soils of Kerala.

Abstract

A comprehensive approach has to be adopted for efficient fertilizer use, incorporating soil test, field research and economic evaluation of the results for providing a scientific basis for the process of enhancing and sustaining food production as well as soil productivity with minimum environmental degradation, it needs more. Soil testing is one of the best scientific means for quick and reliable determination of soil fertility status. Soil test crop response study in the field provides soil test calibration between the level of soil nutrients as determined in the laboratory and the crop response to fertilizers as observed in the field for predicting the fertilizer requirements of the crop. In Kerala, many studies have been conducted to get a fertilizer prescription equation for targeted yield in various crops like rice, banana etc. A programme was formulated to investigate the nutrient interaction in soil test crop response studies on cucumber (Cucumis sativus L.) in the laterite soils of Kerala. In this, the field works were conducted as per the pattern of soil test crop response correlation studies. A gradient crop experiment was conducted in the experimental field of AICRP on STCR using maize. The purpose is to create a fertility gradient in the field by applying different doses of fertilizers. The area was divided into three strips and the doses of nutrients were applied as per STCR pattern of fertilization for maize. The crop was harvested and the plant samples were taken for analysis. The pre and post experimental soil samples were analysed. It was found that fertility gradients were developed in the field. Using the data on dry matter production in various strips, the nutrient uptake was also determined. A test crop experiment was designed in the same field where the gradient crop was raised. There were 24 treatments with three control plots. The treatments included four levels of nutrients and three levels of farm yard manure. The crop, cucumber (Var.: AAUC-2), popularly known as salad cucumber, was raised and managed as per package of practices of KAU. The soil samples were collected before, at flowering and harvest stages during the experiment. The plant samples were collected at flowering and harvesting stages. The total dry matter production and yield were taken treatment wise at the harvest. The soil samples were analysed for various chemical parameters. The data on yield, uptake of nutrients, nutrient status, nutrient requirement, quantity of farm yard manure applied were used for formulating the fertilizer prescription equations for cucumber. Using these equations, the quantity of fertilizers to be used to get a target of yield can be calculated if the available nutrient status is known. The equations thus developed were verified in farmers' field at four locations; Pallikandam, Maraikkal, Ayiloor and Vithanassery. The fields were laid out with five treatments and four replications. The treatments were (i) farmers' practice (ii) KAU package, (iii) soil testing laboratory method, (iv) STCR method with a target of 30 t ha-I and (v) STCR method with a target of 35 t ha-I. The soil samples were analysed before raising the crop and the quantities of fertilizers to be applied were computed for various treatments. The plant and soil samples at flowering and harvest stages were analysed for pH, EC, CEC, Organic Carbon, available N, P, K, Ca, Mg, and micronutrients such as Fe, Mn, Cu and Zn. The total dry matter production and yield were taken treatment wise at the harvest. The data were used for- statistical analysis for assessmg direct and indirect effect of nutrients on yield and nutrient interactions. A positive correlation was observed between organic carbon' and soil parameters at flowering stage. At the harvesting stage, there was a positive correlation was found between yield and major nutrients. The interaction between available P in the soil and Nand K in the plant was observed. The availability ofP in plant was negatively correlated with Fe in the soil. The targeted yield equations for cucumber could produce the yields of 30 and 35 t ha-I from the verification experiments conducted at the different locations. The B:C ratio also was higher in the STCR methods over the farmers' practices, blanket recommendations and STL recommendations. The information generated in the project will help in making the soil testing programme scientifically sound in terms of achieving predicted yields, maintaining soil fertility and helping the extension agencies in ensuring balanced fertilizer use according to the soil fertility status and crop requirement.