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Session 3B: "Soil & Water: Modelling and Implications"
1:20pm - 2:40pm
Session Chair: Ramanathan Sri Ranjan
1:20pm - 1:40pm
Field evaluation of evapotranspiration models under Canadian Prairie conditions
Emeka Ndulue, Ramanathan Sri Ranjan
University of Manitoba, Canada
An accurate estimate of evapotranspiration (ET) is important for determining the water demand of field crops, irrigation scheduling, field water management, and hydrological modeling. The ET can be directly determined by measuring the water uptake of the plant either using a lysimeter or by transpiration flow measurement methods. Since direct measurements are costly weather data has been used as input in various ET models to predict potential ET. This study aims at directly measuring crop ET and comparing it with those predicted by different ET models using meteorological data obtained from a field site in Manitoba.
1:40pm - 2:00pm
Predicting field trafficability under different drainage design parameters and weather patterns using HYDRUS (2D/3D)
Krishna Phani Kaja, Afua A. Mante, Ramanathan Sri Ranjan
University of Manitoba, Canada
In the Canadian Prairie climatic conditions, excess soil water content during the cropping season limits the ability of the field to support the vehicular movement, thereby causing loss to cropping season and soil structure. Monitoring soil water content in a field under different water and soil management practices using conventional methods or sensors is expensive. A two-dimensional hydrologic model for an agricultural field with subsurface drainage was generated using HYDRUS (2D/3D) and validated with field-measured data. The validated hydrologic model was used to investigate the impact of different drainage design parameters (spacing - 8 and 15 m, base depths - 0.9 and 1.1 m, two types - controlled and free drains), and three different soil bulk densities. In this study, a modelling scenario is a combination of a drainage design and one soil physical parameter. A modelling scenario is simulated with 30-year (1986-2015) historical precipitation data only for the period during the cropping season. Models with controlled drainage, predicted no trafficable days for most of the rainfall patterns except for 1988, which had the lowest precipitation in the 30-year period. Based on comparisons done among the years with trafficable days in free drainage models are as follows: Models with drains placed at a base depth of 1.1 m predicted 8-14 additional trafficable days compared to drains at 0.9 m base depth. Models with 8 m drain spacing had 2 – 3 more trafficable days compared to 15 m drain spacing.
2:00pm - 2:20pm
Subsurface Tillage Effects on Soil Strength and Crop Yield
University of Saskatchewan, Canada
Questions have arisen about the long-term effectiveness of deep tillage to address physical limitations such as dense sub-horizon Solonetzic soils and compaction occurring in wet cultivated Chernozemic soils. The objective of the study was to evaluate the effect of subsoiling on Solonetzic and Chernozemic cultivated fields in southern Saskatchewan by measuring and mapping soil strength, bulk density and crop yield. Annually cultivated Solonetzic and Chernozemic soils subjected to heavy vehicle traffic compaction were selected and a minimum-till subsoiler imposed subsoiling tillage treatments. Subsoiling was effective in significantly reducing soil strength and soil density in compacted and non-compacted areas of Solonetzic soils, and eliminating issues of elevated soil strength in wheel traffic affected areas. Subsoiling increased water infiltration and air permeability at both sites. At both the sites, plant yields were not significantly affected by compaction or subsoiling treatments, but there was a trend for subsoiling to result in increased canola yield at the Solonetzic site. Abundant rainfall was received at both sites during the 2016 growing season and this environmental factor could have limited the beneficial effects of subsoiling on soil properties to be revealed in a yield increase. Wheat yields among compacted and non-compacted subsoiled and non-subsoiled treatments were similar at the Chernozemic site. Subsoiling to improve soil properties and yield will be more economical when it is applied to just the known compacted zones in a field, where its effects on properties like soil strength, water and air permeability are manifested to the greatest extent.