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Effect of irrigation and fertigation schedules on yield of cabbage (Brassica Oleracea var. Capitata)

The field experiment was conducted during 2016-2017 and 2017-2018 to investigate the effect of irrigation and fertigation schedules on yield of cabbage during the winter season at AICRP on Water Management, VNMKV, Parbhani. Drip method with alternate day irrigation was adopted for all the plots with five irrigation levels as main plot viz., 0.4 ETc (I1), 0.6 ETc (I2), 0.8 ETc (I3), 1.0 ETc (I4) and 1.2 ETc (I5). Fertigation levels were 50% (F1), 75% (F2) and 100% (F3) of recommended dose of fertilizers (120:60:60; N: P2O5:K2O kg ha) with eight splits during crop growth period. All the treatments were replicated thrice. The treatment combination of 1.0 ETc with 125% RDF, 1.0 ETc with 100% RDF and 0.8 ETc with 100% RDF give comparable and better cabbage yields. Hence the combination treatment of drip irrigation at 0.8 ETc and fertilizer level of 100% RDF may be adopted to obtain higher yields with net saving in water and fertilizers. The economic analysis of cabbage under drip fertigation also suggests that the drip irrigation at 0.8 ETc and fertilizer level of 100% RDF is more economical and feasible as compared to all other combinations.


Introduction
Cabbage, one of the important vegetable crops, requires comparatively more water and nutrients in precise quantity and is very sensitive to moisture and nutrient stress. Conventional methods of irrigation and fertilization results in losses of water and nutrients through leaching, surface runoff, absorption on clay fraction and also create adverse condition for plant growth like water logging to some extent. Nevertheless, water scarcity and high input cost of fertilizer are other constraints in increasing the area, production and productivity of cabbage. Drip fertigation therefore is the most suitable option, which can efficiently use and save water and fertilizer in addition to increase in the area along with increasing productivity. Research on drip irrigation conducted so far in India and abroad has shown that this method leads not only the appreciable saving of water but also returns in achieving higher crop yields as compared to surface irrigation method. Much of work has been done on growth and yield response of various vegetable crops under drip including scheduling. Most of the field studies were conducted with irrigation levels based on pan evaporation data. However, the studies on irrigation schedule based on crop coefficient and real time evapotranspiration data and fertigation scheduling are limited. Similarly, the work on vegetable crop growth simulation under various full and deficit water and fertilizer conditions are scanty. In quest of the above considerations, a comprehensive field investigation was carried out in heavy black soil to evaluate the effect of various irrigation and fertigation levels on cabbage (Brassica Oleracea var. Capitata) crop growth and yield.

Material and Methods
Two field experiments were conducted on cabbage (Brassica Oleracea var. Capitata) during two growing seasons: January through May 2017 and 2018 in a split plot randomized block design at Research Farm of All India Coordinated Research Project on Irrigation Water Management, VNMKV Parbhani. The experimental plots were 7.2 x 7.5 m size with a buffer strip of 1 m and 2 m kept between two adjacent plots and within replications, respectively. Drip method with alternate day irrigation was adopted for all the plots with five irrigation levels as main plot viz., 0.4 ETc (I1), 0.6 ETc (I2), 0.8 ETc (I3), 1.0 ETc (I4) and 1.2 ETc (I5).

Irrigation scheduling
Irrigation water was applied as per the irrigation levels at 0.4, 0.6, 0.8, 1.0 and 1.2 times ETc. The daily crop water requirement for cabbage was estimated using crop coefficient and reference crop evapotranspiration. The crop evapotranspiration ETc was calculated using the following equation The daily reference crop evapotranspiration (ETo) was estimated by using daily meteorological data collected from the meteorological observatory. The reference crop evapotranspiration was estimated using the FAO Penman-Monteith equation (Allen et al., 1998) [2] . using the following equation

Crop coefficient
The crop coefficient varies according to crop type, growth stages and local climatic conditions. The FAO-56 curve method was used to estimate the local value of the crop coefficient. The stage wise crop coefficients of cabbage were derived from FAO 56 and were modified as per the climatic parameters of Parbhani by following the standard procedure and guidelines suggested in Allen et al., (1998) [2] .

Fertilizer application
For cabbage the recommended dose of fertilizers as 120:60:60 kg ha -1 N, P and K was used. In fertigation water soluble graded fertilizers such as (Urea, 19:19:19) were applied in 8 splits as per the treatment. The weighted quantity of fertilizers designed for the treatments were dissolved in water by continuous stirring and the fertilizer solution was injected through venturi in the main pipeline by creating the pressure difference.

Field data collection and analysis
In order to study the effect of irrigation and fertigation levels on growth and yield of cabbage crop, the data on the plant and growth attributes of the cabbage crop were collected periodically during the experimental periods (2016-17 and 2017-18). The collected data was analysed further for interpretations. After transplanting 5 plants were randomly selected from each plot and were properly labeled. The crop growth parameters were recorded from these plants approximately at 15 days interval to monitor their growth. The observations at harvest such as weight of curd and curd yield were recorded for all the plants in the plot.

Curd yield of cabbage
Data pertaining to yield of cabbage (q ha -1 ) as influenced by different irrigation and fertigation levels is presented in Table  1.

Effect of irrigation schedules on curd yield
The data furnished in Table 1  Higher yields under F3 (fertigation at 125% RDF) and F2 (fertigation at 100% RDF) may be due to higher application of nutrients, their mobilization and availability at regular interval in required quantity resulting in better yields.

Interaction effects on curd yield of cabbage
The data presented in Table 2, 3 and 4 shows the interaction effects of irrigation schedules and fertigation levels on curd yield of cabbage during 2016-17, 2017-18 and in pooled results. These are also depicted in Fig. 1 through 3. Data presented in Table 1  The pooled results also indicated that the combination I4F3 is superior by recording curd yield of 432.07 q ha -1 over rest of the combinations and was at par with I4F2 (423.54 q ha -1 ) and I3F2 (420.26 q ha -1 ) (Fig. 4.15)

Conclusion
The treatment combination of 1.0 ETc with 125% RDF, 1.0 ETc with 100% RDF and 0.8 ETc with 100% RDF give comparable and better cabbage yields. Hence the combination treatment of drip irrigation at 0.8 ETc and fertilizer level of 100% RDF may be adopted to obtain higher yields with net saving in water and fertilizers. The cost economics of cabbage under drip fertigation also suggests that the drip irrigation at 0.8 ETc and fertilizer level of 100% RDF is more economical and feasible as compared to all other combinations.