PhD

The research project entitled ‘Ecofriendly production of slicing cucumber (Cucumis sativus L.) through organic sources’ was conducted at the Instructional Farm, College of Agriculture, Vellayani during 2003-2005 to evaluate the effect of various organic manures on the nutrient release pattern and enzymatic activity of the soil, its impact on crop performance and soil properties and to study its residual effect on the succeeding crop. Three separate experiments viz., (1) Laboratory incubation experiment (2) Standardization of an organic nutrient schedule for slicing cucumber and (3) Study of residual effect of different organic manures on succeeding amaranthus were conducted to achieve the objectives envisaged.
In the first experiment organic manures such as FYM, poultry manure, neem cake, enriched vermicompost (EVC) (banana trash- cowdung mixture + 1% rock phosphate + Azospirillum + Phosphobacter) and enriched coir pith compost (ECC) (1 tonne coir pith + 1.5 kg spawn (Pleurotus eous and Schizophyllum commune) + 100 kg cow dung + Azospirillum and Phosphobacter each @ 1 kg and rock phosphate and bone meal each @ 0.75 per cent by weight of the coir pith) were compared to evaluate their relative efficiency in releasing nutrients from the soil and on influencing the enzymatic activity of the soil. The experiment was laid out in completely randomised design with six treatments and four replications. The results revealed that various organic manures differed in their nutrient release pattern in soil. Poultry manure mineralized rapidly releasing almost all its nutrients with in a period of 30 to 60 days whereas FYM and neem cake released nutrients slowly over a period of 75 to 120 days. EVC and ECC released nutrients gradually over a period of 60 to 75 days. Available nutrient content was comparatively higher for poultry manure followed by EVC. Soil enzymatic activity was also significantly improved by organic manures and the activity gradually progressed up to 60-75 days and there after declined. Dehydrogenase and protease activities were comparatively higher for neem cake and EVC; phosphatase activity was higher for EVC and poultry manure, urease activity for FYM and EVC and cellulase activity for neem cake and ECC. On a whole, the enzymatic activity was better in soil applied with EVC.
In the second experiment an organic schedule was standardized for slicing cucumber, variety AAUC-2 by comparing the effects of five organic manures [FYM (m1), poultry manure (m2), neem cake (m3), enriched vermicompost (m4) and enriched coir pith compost (m5)] with and without microbial inoculation (Azospirillum + AMF) on growth, yield and quality of slicing cucumber and compare their relative efficiency with the present package of practices (POP) recommendation of Kerala Agricultural University (25 t ha-1 FYM + 70:25:25 kg NPK ha-1 through chemical fertilizers) on equivalent nitrogen basis. FYM @ 25 t ha-1 was applied uniformly in all plots. The experiment was laid out in 5x2+1 factorial randomised block design with three replications. The main effects of organic manures and microbial inoculants and their interaction effects were studied.
The results revealed that application of enriched vermicompost favoured crop growth and yield by recording the maximum vine length, number of branches and leaves, leaf area index, dry matter production, number of male and female flowers, length and girth of fruit, fruit weight and the highest fruit yield as compared to all other manures and POP recommendation. Nitrogen and phosphorus uptake was also highest with EVC application whereas K uptake was highest in poultry manure and neem cake applied plants. EVC application also led to marked improvements in fruit quality by enhancing crude protein content, vitamin C and calcium content of fruits and by improving the shelf life of fruits. Neem cake treated plants produced fruits with the highest iron and crude protein content.
Various growth and yield parameters and total fruit yield were significantly improved by AMF + Azospirillum inoculation. Microbial inoculation resulted in significant improvement in crude protein content and calcium content in fruits in both the years and vitamin C content and iron content in the second year. N and K uptake were also considerably higher for inoculated plants.
Application of various organic manures and microbial inoculants favourably influenced soil physico-chemical properties and the fertility status compared to POP recommendation. Bulk density and particle density of soil were lowest and porosity percent and water holding capacity were highest for neem cake and EVC treated soils. pH and cation exchange capacity were considerably improved and electrical conductivity was decreased by EVC application. The organic carbon content was highest with FYM application. All the above soil physico-chemical parameters except organic carbon content and WHC were considerably improved by microbial inoculation. EVC application resulted in higher nitrogen content in soil whereas poultry manure recorded higher P, K, S and Zn content in soil. AMF + Azospirillum inoculation favourably influenced N, S and Zn content in soil.
Among organic manure-microbial interactions, combined application of EVC and microbial inoculants (m4a1) favoured crop growth and yield attributes and recorded the maximum mean fruit yield (21.06 t ha-1) and was on par with the sole application of EVC (m4a0) (20.45 t ha-1) and these two treatments were significantly superior to all other interactions and POP recommendation of Kerala Agricultural University. Based on these results m4a0 is found to be better for obtaining satisfactorily higher yield. EVC also maintained its superiority in improving various soil physico- chemical properties and soil fertility status.
Organic manures usually have a carry over effect on the succeeding crop. Hence the third experiment was conducted to work out the residual effect of different treatments under experiment II on the productivity of the succeeding amaranthus, variety Arun, which was raised in the previously laid-out plots used for cucumber. The results revealed that the residual effect of various organic manure treated plots was substantially higher as compared to that of chemical fertilizer treated plots (POP recommendation). The highest green yield of 15.07 t ha-1 was recorded in neem cake applied plots and was followed by EVC (14.30 t ha-1). Soil physical properties were considerably improved in plots that had residual organic manures as compared to residual POP. Poultry manure and neem cake application along with microbial inoculation lowered bulk density and particle density and improved porosity and WHC of the soil. Soil pH and organic carbon content were highest for FYM and CEC was highest with EVC application. Residual EVC accumulated highest N content in soil whereas P, K, S and Zn were highest with residual poultry manure. Various physico-chemical properties and soil fertility status was considerably improved by residual effect of microbial inoculation.
Nutrient balance sheets indicated deficit balance of available N, P and K in soil. Combined application of EVC, AMF and Azospirillum proved beneficial in lowering the net losses of N and K whereas net loss of P was lowest with neem cake as compared to all other treatments and POP recommendation.
Economic analysis of various treatments in slicing cucumber showed that application of EVC + microbial inoculants (m4a1) generated higher profit compared to all other treatments. However B:C ratio was highest for POP recommendation followed by m4a1. In the residual study, all organic manures recorded higher net returns and B:C ratio than POP and the highest profit was obtained from neem cake treated plots (m3a0). However analysis of the cumulative net returns from cucumber-cucumber-amaranthus crop sequence revealed that combined application of EVC and microbial inoculants (m4a1) produced the highest net returns and B : C ratio, closely followed by m4a0.
Thus the current research brings out the suitability of enriched vermicompost (banana waste + 1% rock phosphate + Azospirillum + Phosphobacter) as a possible alternative to chemical fertilizers for maintaining high yield of good quality slicing cucumber along with the improvement in soil fertility and health status. Based on the above results, basal application of 25 t ha-1 FYM and 6 t ha-1 enriched vermicompost can be suggested as the best economic organic nutrient schedule for slicing cucumber. The results also revealed that organic manures have a long lasting effect and could be more profitable and sustainable than chemical fertilizers on long term basis.