RAVI BABU, G.CHENNAKESAVULU, B.2022-08-182022-08-182022-08-18D6287https://krishikosh.egranth.ac.in/handle/1/5810186427EFFECT OF DRIP IRRIGATION AND FERTIGATION SCHEDULING ON SOIL MOISTURE AND NITROGEN DISTRIBUTION PATTERNS UNDER HIGH DENSITY PLANTING OF GUAVA (Psidium guajava L.)Water and land are two essential resources for agricultural growth and economic development of any country and shall not be considered as available in abundance and free forever. Due to increase in population, the requirement for these two resources shall continue to grow day by day. The key inputs which directly affect the plant growth and development, yield and quality of produce are irrigation and fertilizer. Application of irrigation water and fertilizers through drip irrigation system is the most effective way of supplying water and nutrients to the plants. The present experiment was conducted on guava crop with the variety of VNR bhihi to study the influence of frequency of nitrogen and irrigation management on the movement of nitrogen ions in the soil under the high density planting. The purpose of this study was to observe the water movement under four irrigation treatments and its role in nitrogen distribution under four fertigation frequencies and their effect on guava yield. Experiments were conducted at research farm of college of horticulture, Venkataramannagudem, West Godavari district of Andhra Pradesh to study the effect of different irrigation and fertigation levels on plant growth, yield, soil moisture and nitrogen distribution patterns of guava under high density planting system. The experiment was laid out in a Factorial Randomized Block Design (FRBD) with sixteen treatments and each replicated thrice. During crop growth period four levels of irrigation water (120 % of ETc, 100 % of ETc, 80 % of ETc and 60 % of ETc) and four levels of recommended dose of fertilizers (120 % of RDF, 100 % of RDF, 80 % of RDF and 60 % of RDF) were imposed. Soil samples were taken from different depths (both vertically (90 cm depth) and horizontally from the dripper to study the soil moisture and nitrogen distribution patterns during crop growth period. Soil sampling was done three times in the growing period (i.e. 30 days after pruning) vegetative stage, (90 days after pruning) mid stage and (150 days after pruning) harvesting stage during both the seasons of 2018-19. A finite element model Hydrus-2D was selected to simulate the water and nitrogen movement in the root zone. Simulations were done in axi-symmetrical polar coordinate system for the radius of 30 cm and depth of 90 cm. xviii Analysis of crop performance parameters (based on pooled data) revealed that treatment T5 (I2F1) gave 39% more yield compared to T16 (I4F4) treatment. Irrigation, fertigation and their interaction had significant effect on water use efficiency and nitrogen use efficiency. WUE was highest in T13 (I4F1) (224.93 kg ha-1 mm-1and 226.12 kg ha-1 mm-1) in first and second season respectively. NUE was found significantly higher in T8 (I2F4) treatment (128.77 and 130.00 kg kg-1) during first and second Seasons. The moisture distribution patterns 48 h after irrigation for different irrigation levels were at field capacity and soil is at saturation at emitter, 15 cm away from the emitter and 22.5 cm away from the emitter in horizontal plane. The analysis of results also revealed that the moisture content for I1 and I2 treatments in the top two soil layers were at field capacity and soil is at saturation at emitter, 15 cm away from the emitter and 22.5 cm away from the emitter in horizontal plane. However, there was a deficit in moisture content in the top soil layer also for I3 and I4 treatments. It was noticed that higher values of nitrogen concentration was found in top 30 cm soil profile in all the four levels of fertigation. This may be due to the presence of more ammonical nitrogen in this layer because of more moisture content. In the lower soil profiles lower nitrogen concentration were observed in all the four levels of fertigation treatments. Similar trend was also observed in T5 (I2F1) , T6 (I2 F2), T7(I2F3) and T8(I2F4) treatments respectively at 48 h after fertigation. The lowest nitrogen concentration was recorded in T8 treatment in the lower soil profiles. This may be due to lower (60 % of RDF) application of nitrogen in that particular treatment. The simulation results for soil water and nitrogen distribution by HYDRUS-2D model revealed that, there was a good agreement between observed data in the field experiment and predicted by model. The results provide support for using HYDRUS-2D as a tool for investigating and designing drip irrigation management practices The economic analysis was done for guava crop cultivation under drip irrigation. The highest benefit cost ratio (4.6 in season -1 and 5.8 in season -2) and lowest payback period (21 months in season -1 and 18 months in season-2) was found in treatment I2F1 during the crop period. Hence, I2F1 treatment may be more beneficial for the farmers. Key words: Drip irrigation, fertigation, HYDRUS-2D, soil moisture content, nitrogen content, benefit cost ratio.EnglishThesis