Impact of irrigation and fertigation levels on growth, yield and quality of summer chilli (capsicum annuum L.)
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Date
2020-02-06
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Vasantrao Naik Marathwada Krishi Vidyapeeth, Parbhani
Abstract
Water is the vital source for crop production and is the most limiting factor in Indian agricultural scenario. Though India has the largest irrigation network and even if the full irrigation potential is exploited, about 50% of the country’s cultivated area will still remain unirrigated, particularly with the current level of irrigation efficiency not exceeding 40%. Conventional irrigation systems such as basin irrigation and wild flooding apply comparatively larger quantity of water per irrigation leading to huge loss of water in the form of surface runoff, evaporation and deep percolation. To achieve required food and fibre production with increasing population, India has to enhance the current irrigation potential of 91 M ha to 140 M ha. In view of worsening water scarcity and raising water demand, the available water resources should be very effectively utilized through water saving irrigation technologies.
Fertilizer is the costliest input after water, in agriculture. Apart from the economics consideration it is also well known that the adverse effect of injudicious use of water and fertilizer on the environment can have far reaching implications. There is, therefore, a need for technological options, which will help in sustaining the precious resources and maximizing crop production without any detrimental impact on the environment.
Chilli (Capsicum annuum L.) belongs to the Solanaceae family, is one of the important vegetable-cum-spice crops of India. India is the largest producer, consumer and exporter of chilli, which contribute to 25% of total world’s production. Chilli being a long duration crop, it responds to split application of nutrients i.e., nitrogen, phosphorus and potassium. It responds well to fertigation with 11 to 22 applications in terms of increased growth and yield properties besides, higher water and fertilizer use efficiencies compared to conventional methods of fertigation. Pungency and colour are two important characters liked by consumers.
Accurate crop development models are important tools in evaluating the effects of water deficits on crop yield or productivity. Food and Agricultural Organization (FAO) of United Nations addresses this need by providing a yield response to water simulation model (AquaCrop) with limited sophistication. It simulates crop yield response to water, and is particularly suited to address conditions where water is a key limiting factor in crop production.
Keeping these points in view, the present investigation was undertaken with the specific objectives of studying the effect of different drip irrigation and fertigation levels on growth, yield and yield attributes, quality, water and fertilizer use efficiency in chilli. Also field results were used to calibrate and validate AquaCrop model for chilli in Marathwada region.
In order to fulfil the objectives of the study, the field experiment was conducted in split plot design with fifteen treatment combinations, replicated thrice during the years 2018 and 2019 at Experimental farm, College of Agriculture, Badnapur.
The results of the experiment indicated that Effect of different drip irrigation levels on growth parameters viz., plant height, number of branches and plant spread of chilli was studied and the results revealed that, drip irrigation at 1.00 ETc was found to be significantly superior among the different drip irrigation levels. However, it was found at par with drip irrigation level at 0.90 ETc and at 0.80 ETc during 2017-2018 and 2018-2019 and in pooled results. Thus drip irrigation at 0.8 of crop evapotranspiration was found to be optimum among all tested treatments. Whereas, application of different levels of fertigation in eleven split had non-significant effect on plant height and plant spread of chilli at 30 and 60 DAT and found significant at 90 and 120 DAT. Further fertigation with 100 per cent of RDF and 80 per cent of RDF were found statistically at par with each other for the above growth parameters at various stages of crop growth. Therefore, fertigation with 80 per cent RDF in eleven splits was found to be optimum. Interaction effect of different drip irrigation and fertigation level was found non-significant.
Impact of different drip irrigation levels on per cent fruit set, root length and total dry matter production of chilli was studied and results indicated that drip irrigation at 1.00 ETc was found to be significantly superior among the different drip irrigation levels. However, it was found at par with drip irrigation at 0.90 ETc and at 0.80 ETc during 2017-2018 and 2018-2019 and in pooled results. Thus drip irrigation at 0.8 of crop evapotranspiration was found to be better among all the tested treatments. Whereas, among the different levels of fertigation in eleven splits, fertigation with 100 per cent of RDF and 80 per cent of RDF were found statistically at par with each other in case of per cent fruit set, root length and total dry matter production of chilli. Therefore, fertigation with 80 per cent RDF in eleven splits was found optimum. Interaction effect of different drip irrigation and fertigation level was found non-significant.
Significant differences on chilli yield and yield attributes viz., fruit length, girth and number of fruits per plant were observed in pooled results for different drip irrigation and fertigation levels. Among drip irrigation levels the yield attributes obtained under drip irrigation at 1.0 ETc were recorded significantly higher for fruit length (9.31 cm), fruit girth (4.96 cm), fruit weight (5.21 g) and number of fruit per plant (103.30) over rest of the irrigation levels. However, it was found at par with drip irrigation level at 0.9 ETc (fruit length 9.15 cm, fruit girth 4.79 cm, fruit weight 5.02 g and number of fruit per plant 101.19) and drip irrigation level at 0.8 ETc (fruit length 8.93 cm, fruit girth 4.74 cm, fruit weight 4.95 g and number of fruit per plant 99.27). Lowest fruit length (7.28 cm), fruit girth (3.93 cm), fruit weight (4.46 g) and number of fruit per plant (74.02) were recorded in drip irrigation level at 0.7 ETc. Thus, drip irrigation level at 0.8 of crop evapotranspiration was found to be optimum.
Whereas, pooled results for different fertigation levels, fertigation with 100 per cent of RDF and 80 per cent of RDF found statistically at par with each other for the yield attributes of chilli. Fertigation with 100 per cent RDF recorded significantly higher fruit length (9.17 cm), fruit girth (4.90 cm ), fruit weight (5.19 g) and number of fruit per plant (104.05) and was found statistically at par with fertigation with 80 per cent RDF (fruit length 8.87 cm, fruit girth 4.62 cm, fruit weight 4.95 g) and number of fruit per plant 99.70) but superior than 60 per cent RDF (fruit length 7.93 cm, fruit girth 4.28 cm, fruit weight 4.61 g and number of fruit per plant 72.00). Therefore, fertigation with 80 per cent RDF was said to be good enough. Interaction effect of different drip irrigation and fertigation level was found non-significant on yield attributes of chilli.
Yield of chilli recorded under drip irrigation at 1.0 ETc was found significantly higher (15.90 tonnes ha-1) over rest of the irrigation levels. However, it was found at par with drip irrigation level at 0.9 ETc (15.38 tonnes ha-1) and drip irrigation level at 0.8 ETc (15.15 tonnes ha-1) in pooled results. Lower yield was noticed in drip irrigation at 0.7 ETc treatment (12.72 tonnes ha-1). Thus, drip irrigation level at 0.8 of crop evapotranspiration was found to be optimum.
Similarly pooled results, for different fertigation levels, yield of chilli recorded under fertigation with 100 per cent of RDF (16.36 tonnes ha-1) was found to be significantly superior to 60 per cent of RDF (12.80 tonnes ha-1) and was at par with 80 per cent of RDF (15.20 tonnes ha-1). Interaction effect of different drip irrigation and fertigation level was found non-significant on yield of chilli.
Pooled results indicated that the highest ascorbic acid content of chilli was recorded in drip irrigation level at 1.0 ETc (118.51 mg 100g-1) and found statistically at par with drip irrigation level at 0.9 ETc (117.32 mg 100g-1) and drip irrigation level at 0.8 ETc (116.88 mg 100g-1). Lowest ascorbic acid content of chilli was recorded in drip irrigation level at 0.7 ETc (108.65 mg 100g-1). Therefore, drip irrigation level at 0.8 of crop evapotranspiration was found to be optimum.
Fertigation with 100 per cent RDF resulted in highest ascorbic acid content of chilli (118.52 mg 100g-1), which was noticed statistically at par with fertigation with 80 per cent of RDF (116.01 mg 100g-1) in pooled results. Lowest ascorbic acid content of chilli was recorded in treatment fertigation with 60 per cent of RDF (111.28 mg 100g-1). Thus, fertigation with 80 per cent RDF was found to be good enough. Interaction effect of different drip irrigation and fertigation level was recorded non-significant on ascorbic acid content of chilli.
The different drip irrigation levels had recorded non-significant effect on oleoresin content of chilli. Oleoresin content was found significantly highest in the treatment fertigation with 100 per cent of RDF (15.41 %) over rest of treatments, but found statistically at par with 80 per cent of RDF (14.60 %) in pooled results. Lowest oleoresin content of chilli was recorded in treatment fertigation with 60 per cent of RDF (13.66 %). Therefore, fertigation with 80 per cent RDF was found to be optimum. The interaction effect of different drip irrigation and fertigation levels did not significantly influence the oleoresin content.
The total amount of water applied at different levels of drip irrigation during 2017-18 and 2018-19 was maximum for drip irrigation at 1.1 ETc i.e 655 and 718 mm, respectively, followed by drip irrigation at 1.0 ETc i.e 596 and 653 mm, respectively and minimum in case of drip irrigation at 0.7 ETc i.e 417 and 457 mm, respectively.
For different drip irrigation levels, the treatment drip irrigation level at 0.8 ETc recorded highest water use efficiency of 30.48 q ha-1 cm-1, whereas lowest water use efficiency of 21.68 q ha-1 cm-1 was noted under drip irrigation level at 1.1 ETc in pooled results. Thus, drip irrigation level at 0.8 of crop evapotranspiration was found to be superior among the tested treatments.
In case of pooled results for different fertigation levels, treatment fertigation with 100 per cent RDF recorded the highest water use efficiency of 29.69 kg ha-1 cm-1 which was found at par with 80 per cent RDF (27.69 kg ha-1 cm-1). Whereas, lowest water use efficiency of 23.00 kg ha-1 cm-1 was noticed under treatment fertigation with 60 per cent RDF. Thus, fertigation with 80 per cent RDF was found to be optimum. The interaction effect on water use efficiency by different drip irrigation and fertigation levels was found non-significant.
Water use efficiency increased with decrease in the depth of irrigation water applied. In order to have higher water use efficiency, drip irrigation should be scheduled at an alternate day with 0.8 ETc depth of irrigation. For better yields and high water use efficiency of chilli, application of drip irrigation at 0.8 ETc and fertigation with 80 % of RDF were found to be better.
For fertilizer use efficiency non-significant differences were found, when crop received drip irrigation levels between 80 to 100 per cent of crop evapotranspiration. Whereas in different fertigation levels, treatment 60 per cent of RDF recorded highest fertilizer use efficiency of 41.05 kg kg-1 which was found statistically at par with 80 per cent RDF having 37.36 kg kg-1 in pooled results. Lowest fertilizer use efficiency of 32.35 kg kg-1 was recorded under treatment fertigation with 100 per cent RDF. The interaction effect on fertilizer use efficiency by different drip irrigation and fertigation levels did not differ significantly.
Fertilizer use efficiency increased with decrease in quantity of fertilizer applied. In order to have higher feritlizer use efficiency, fetigation with 80 per cent of RDF was found to be optimum.
Effect of different drip irrigation levels on uptake of nitrogen revealed that drip irrigation at 1.0 ETc recorded significantly higher uptake of nitrogen (40.95 Kg ha-1) as compared to other drip irrigation levels and was statistically at par with drip irrigation at 0.9 ETc (39.19 Kg ha-1) and drip irrigation at 0.8 ETc (37.93 Kg ha-1) in pooled results. Lowest values for uptake of nitrogen was recorded in treatment drip irrigation at 0.7 ETc (24.21 kg ha-1). Similar trend was observed for uptake of phosphorus and potassium.
Regarding fertigation levels, fertigation with 100 per cent RDF registered significantly higher values for uptake of nitrogen (38.77 Kg ha-1) which was found at par with 80 per cent RDF (36.30 kg ha-1) in pooled results. Lowest values for uptake of nitrogen was recorded for treatment fertigation with 60 per cent RDF (30.50 Kg ha-1). Similar trend was observed for uptake of phosphorus and potassium. The interaction effect on uptake of N, P and K by different drip irrigation and fertigation levels was found non-significant.
Economic analysis for chilli indicated that among drip irrigation levels, the B:C ratio for treatment drip irrigation at 1.0 ETc was recorded comparatively highest (3.52) over rest of the irrigation levels. It was followed by drip irrigation level at 0.9 ETc (3.44) and drip irrigation level at 0.8 ETc (3.40) in pooled results. Lowest B:C ratio was recorded for treatment drip irrigation at 0.7 ETc (2.92). Similar trend was observed for GMR and NMR. Thus drip irrigation level at 0.8 of crop evapotranspiration was found to be optimum.
Whereas, in different fertigation levels, fertigation with 100 per cent of RDF recorded highest B:C ratio (3.49) followed by 80 per cent of RDF (3.40). Lowest B:C ratio was recorded for treatment fertigation with 60 per cent of RDF (3.03). Similar trend was observed for GMR and NMR. Thus, fertigation with 80 per cent of RDF was found optimum for GMR, NMR and B:C ratio.
Results from this study provided a set of first estimates for the calibration of the AquaCrop model on chilli for agro-climatic conditions particularly in Jalna District and in general, for further testing and validation of the model at other agro-climatic conditions. AquaCrop model was calibrated by using field data of full irrigation (drip irrigation at 1.0 ETc) treatment with harvesting index of 75 per cent and water productivity 30 gm-2 as there was close match between observed and simulated canopy cover with high value statistical parameter of R2NS =0.97 and CRM = -0.051. It was also found that the canopy cover was overestimated by model particularly during 36 to 84 DAT i.e. during development stage. It was also seen from scatter plot that as the canopy cover values lies on both sides of 1:1 line, there was no consistent over or under estimation.
AquaCrop model was validated for its performance under deficit and fully irrigated treatments. Validation results indicated that AquaCrop model predicted well, having only -2.54 per cent average variation between observed and simulated yield values with Nash Sutcliffe coefficient (R2NS) value 0.82. Coefficient of Residual Mass (CRM) value was found as -0.044, which indicated that model overestimates the yield, likewise during calibration.