RAGHU BABU, MOVVASAMBAIAH, ANGIREKULA2019-05-212019-05-212018http://krishikosh.egranth.ac.in/handle/1/5810104098D5746Sugarcane (Saccharum officinarum L.) is an important commercial crop with a production of 300 M t and 16 M t in India and Andhra Pradesh, with a productivity of 71.1 and 76.3 t ha-1 respectively. But the potential areas are withdrawn from sugarcane cultivation due to low yields ranging from 44 t ha-1 to 56 t ha-1 owing to the severe waterlogging problem in the present study area, Kapileswarapuram of East Godavari district, Andhra Pradesh. In this context, to solve this problem of waterlogging, an attempt has been made to intervene with a consortium of technologies viz., mole drainage systems and soil oxygenation to test the performance of sugarcane, model the mass and solute transport and evaluate economically for viability of the technology consortium. The scientific methods were followed to conduct pre-mole drainage investigations to find the soil characteristics, hydrological regime and groundwater table fluctuations and post drainage observations on soil, rainfall, runoff, preferential flow, drainage water, plant growth and yield attributes and economic analysis of the same. Extensive study of literature suggested that there is a minimal work conducted on mole drainage systems, as well as on soil oxygenation, that too in sugarcane, which is waterlogging sensitive crop, despite mole drainage system being very easy and low cost method of subsurface drainage and Calcium peroxide (soil oxygenation agent) being a harmless chemical, which releases oxygen in submerged conditions to the rootzone for about 14 weeks in the soil. Keeping the above points in view, the present study was undertaken to develop the consortium of technology to solve the problem of waterlogging in sugarcane. The soil texture of the study area is black soil with clay content of 52.87%, silt content of 33.25% and with sand content of 13.88%. This soil presented a bulk density of 1.15 g cm-3, with at plastic limit of 32.33%. The soil is slightly saline with ECe of 1.73 dSm-1 and pH of 7.89. The terrain of the experimental field was brought to 0.30% uniform xxii slope to avoid experimental bias and to facilitate grade to mole drains. The average saturated hydraulic conductivity of the study area soil profile is measured with auger hole method and found to be 0.30 m d-1(Pre-mole drainage) and 0.50 m d-1 (Post-mole drainage). The average depth of groundwater table is 0.30 m, b.g.l. Rainfall probability analysis revealed that the 1-day maximum rainfall event with 5-years return period is 157.0 mm which produces 101.4 mm of surface runoff and rest 55.60 mm abstraction into the soil, which upon moling, becomes drainage co-efficient for the mole drains. The SEW30 index for the study area is very high i.e. 2891.0 cm-days, double the sugarcane threshold limit. Using, the theory of Hooghoudt’s equation with additional assumptions for mole drainage spacing design, the mole drain spacing was designed to be 2 and 3 m and for sensitivity analysis purpose, 4 and 5 m spacing mole drains were also studied. The depth of mole drains were chosen to be placed at 0.4 and 0.5 m b.g.l as the 90% of the effective rootzone of sugarcane is found within 0.5 m below ground level. As an agent of soil oxygenation, calcium peroxide was chosen with an application rate of 2 g plant-1 placed at 15 cm b.g.l at midway between the plants. The experimental design selected is split-split plot design with four replications. Sugarcane variety of Co 86032 (Nayana) was selected for the study which has highest yield potential of 110.0 t ha-1, which is waterlogging sensitive variety. The seedling rate considered for the study is 25000 of seedlings ha-1 with paired row transplantation at a row to row spacing of 1.35 m and plant to plant spacing of 30 cm in zig-zag pattern. The maximum plant height at 305 DAS is 465.5 cm in 0.4 m depth mole drains with a mole drain spacing of 3 m under soil oxygenation treatment and 416.5 cm in 0.5 m mole drain depth plot with 2 m spacing with soil oxygenation, which is less than what was achieved in 0.4 m mole drain depth treatment. The average plant height in check plot WOSO (Farmer’s practice) was found to be 198.25 cm only. The sugarcane yield is the net effect of the all the treatments, which revealed that the average maximum yield of 108.92 t ha-1 was attained in 0.4 m mole drain depth with 3 m mole drain spacing and followed by 103.89 t ha-1 in 0.5 m mole drain depth with 2 m mole drain spacing and 3 m spacing in 0.5 m mole drain depth plots with soil oxygenation. In WOSO treatments, sugarcane yield of 93.08 and 92.74 t ha-1 was realised in in 0.4 m MDD - 3 m MDS and 0.5 m MDD - 2 m MDS respectively. The yield in check treatment under SO was found to be 64.60 t ha-1 and 57.91 t ha-1 in WOSO. The yield under the consortium of mole drainage and SO resulted in 88.0% more yield than check plot without soil oxygenation. The behaviour of the sugarcane yield in mole drainage systems has followed 3rd order polynomial equations in all the cases with highest co-efficient of determination ranging from 0.96 to 0.99. The total cost of mole drainage system installation was worked out to be ₹ 8,200.00, out of which, 44.0% cost goes into digging of the collector drain, 18.3% cost goes into outlet protection, 22.0% goes into actual mole plough operation. The expected life of mole drains is 3 years. The recurring cost for making moles from 4th year onwards will be only ₹ 2,300.00 for every three years, including the labour costs of ₹ 800.00 at 2016-17 prices. With the farmers practice in waterlogged soils, a loss of 16-22 paise on every rupee of investment is incurred despite the subsidy being given. In pre-drainage condition, the B:C ratio is 0.78, i.e. found to be below 1 and the net present worth is less than 0 (Negative), which infers that sugarcane cultivation in waterlogged vertisols is not a viable option to the farmers. To make it viable, either more subsidy is to be given or technologies are to be developed. In, 0.4 m mole drain depth installation, mole drainage systems with 2, 3, 4 and xxiii 5 m are found viable in consortium mode with soil oxygenation with a B:C ratio of 1.16, 1.22, 1.08 and 1.03 respectively and average IRR of 14.62%. Without soil oxygenation, only 2, 3 and 4 m are viable with B:C Ratio of 1.07, 1.13 and 1.03 respectively. But the maximum B:C ratio of 1.22 and 1.13 was achieved in 3 m spacing mole drains both in with soil oxygenation and without soil oxygenation. In 0.5 m mole drain depth installation, mole drainage systems with 2, 3 and 4 m are found viable in consortium mode with soil oxygenation with a B:C ratio of 1.19, 1.16 and 1.05 respectively with average IRR of 14.62%. Without soil oxygenation, only 2 and 3 m are viable with B:C ratio of 1.13 and 1.09 respectively. But the maximum B:C ratio was found in 2 m spacing mole drains both in with soil oxygenation and without soil oxygenation as 1.19 and 1.13 respectively. In conclusion, it can be said that the surface drainage co-efficient (overland flow) is found different from the mole drainage co-efficient (preferential flow of abstraction) and the new method adopted in the present study can be used in future. The mole drainage systems could handle larger drainage co-efficients such as 55.6 mm d-1 as in case of Kapileswarapuram. Hooghoudt’s equation was employed successfully for the design of mole drain spacing without considering the equivalent depth concept in this study. The hydraulic conductivity of the vertisol changed upon installation of mole drains from 0.3 to 0.5 m d-1 and bulk density decreased. Mole drains laid at 0.4 m depth with 2 and 3 m spacing could handle the maximum drainage flow depth of 46.1 mm d-1 of abstraction in 19.8 and 29.0 h respectively and the same was evacuated by 0.5 m depth with 2 and 3 m could in 24.4 and 35.7 h from the sugarcane fields. Soil oxygenation, a new concept studied using calcium peroxide granular powder placement in the sugarcane crop root zone proved successful in sugarcane and can be a component of consortium for mole drainage technology. Soil oxygenation agent (Calcium peroxide) did not cause any increase in soil salinity. The SEW30 index of the region was reduced from 2891 cm-days to 150 cm-days, which is far below the threshold limit of sugarcane crop. The mass and solute transport models developed and simulations using Hydrus-1D are useful for similar situations and regions. The mole drains at 0.4 m with 2 m and 3 m spacing could bring down the soil moisture to field capacity. Mole drainage systems along with soil oxygenation agents improved the oxygen reduction potential of the soil to +752 mV (Good aerated condition) from highly reduced conditions with -567 mV during heavy rainfall event. The mole drainage systems installed at 0.4 m depth at 2 and 3 m spacing could reduce the soil salinity by 65 and 50%, respectively. The mole drainage system installed at 0.5 m MDD at 2 m and 3 m spacing could reduce the soil salinity by 61 and 47% respectively. The sugarcane yield increased by 96.6% under mole drains installed at 3 m MDS at a depth of 0.4 m MDD along with soil oxygenation. The combination of mole drainage systems with soil oxygenation could bring up the BCR to 1.22 and NPW from negative to positive. Adoption of mole drainage systems with soil oxygenation using calcium peroxide granular powder provides 20-29 paise return on every rupee of investment in sugarcane. The models of mass and solute transport developed in the present study can be applied to similar situations encountered. New method for mole drainage design was developed by modifying the Hooghoudt’s assumptions. Another novel concept of low cost consortium of mole drainage with soil oxygenation is successfully experimented in waterlogged sugarcane vertisols and a new term “Draining capacity” is defined in the present study. Key words: Mole drainage, soil oxygenation, calcium peroxide, oxygen reduction potential, draining capacity, B:C ratio, Internal Rate of Return, Net Present Worth, SEW30 index, mole drainage co-efficient, waterlogging, salinity, Hydrus-1D.en-USnullThesis