EFFECT OF COATED CALCIUM CARBIDE ON GROWTH, YIELD AND SOME MORPHOPHYSIOLOGICAL CHARACTERISTICS OF CUCUMBER (Cucumis sativus L.)

Abstract

Ethylene is involved in regulation of various aspects of plant growth and development and also acts as a defense mechanism under various stress conditions. A lot of work on foliarapplied source of ethylene has been evaluated as a mean to improve growth and yield of various crops in literature. Little research has been published on the use of soil-applied ethylene source for vegetable production. The objective of this project was to evaluate the effect of calcium carbide based formulation, a soil-applied source of ethylene, on growth, yield and some morpho-physiological characteristics of cucumber. Laboratory, pot and field studies were conducted in a sequence to investigate the effect of calcium carbide (CaC2) on seed germination, growth, yield, nitrogen and carbon metabolism and fruit quality parameters. Preliminary studies (experiment 1 to 3) were conducted under controlled conditions to evaluate the effect of CaC2 on seed germination, growth and some metabolic changes in cucumber seeds under normal and stress conditions. Results showed that application of 30 mg plate-1 CaC2 among different rates was found the best rate to promote seed germination and growth of plants. Increase in germination percentage, growth parameters and nitrogen assimilation was noted in response to 20 and 30 mg CaC2 plate-1 while higher rate of CaC2 than 30 mg plate-1 was, however, found to inhibit physiological functions. Seed germination was inhibited under salt stress, and this inhibitory effect was significantly mitigated by the addition of CaC2 in the incubation medium along with increased ethylene evolution. Application of CaC2 also increased the contents of soluble sugars, soluble proteins, free amino acids and activity of α-amylase and antioxidant enzymes in response to CaC2 under salt stress. The 4th experiment was conducted in pot where different rates and coating materials on CaC2 were optimized under soil conditions for growth and yield attributes of cucumber. All rates of CaC2 significantly improved growth and yield parameters but effect of coating materials was less significant. However, maximum fruit yield was obtained in the treatment of 300 mg paint coated CaC2 pot-1. In the light of the results of experiment 4, another pot experiment was conducted to investigate the genotypic response of two cucumber cultivars (Hybrid vs. Local) to soil applied paint coated CaC2 which significantly improved morphological, phenological and yield characteristics of both cultivars but hybrid cultivar (Bolan-F1) surpassed local cultivar (Desi) regarding yield characteristics. Finally a field experiment of was conducted to investigate effect of paint coated CaC2 on photosynthesis, nitrogen use efficiency and fruit quality of cucumber under deficient and adequate levels of nitrogen. Application of paint coated CaC2 at each level of nitrogen increased photosynthesis via increase in nitrogen assimilation and stomatal conductance. Plants treated with 300 mg CaC2 with sufficient nitrogen exhibited maximal photosynthesis and growth characteristics. These plants also showed maximum nitrogen uptake, nitrogen use efficiency and mineral contents along with improved fruit quality characteristics. Overall results suggest that application of 300 mg plant-1 paint coated CaC2 enhanced fruit yield by 39.6% compared to control by improving yield contributing factors. These results suggest that application of CaC2 at right rate with appropriate coating material could significantly improve the quality and fruit yield in cucumber by making economic use of soil applied nitrogen.