added 2 research items
Microalgae are widely used for wastewater treatment. Microalgae offer several advantages over other microbial culture used in wastewater treatment. Some of these advantages are (i) low-cost cultivation at large scale without external supply of nutrient and carbon, (ii) ability to sequester CO2 from waste gases, and (iii) production of biochemical-rich biomass which can be used for biofuel production or as animal feed. Further, research reports revealed that algal-bacterial co-culture has number of advantages over pure algal cultures in wastewater treatment. Microalgae and bacteria in wastewater systems usually have synergistic relation, resulting in improved remediation and enhanced biomass production. However, these interactions are affected by several operational conditions such as nutrient profile, pH, and temperature. Indeed, the algal-bacterial synergies are situation based and may change significantly even with a slight change in the operational conditions. In the recent years, in-depth research and development has been carried to overcome the process limitations particularly for wastewater treatment using algal-bacterial co-cultures. Moreover, attempts have also been made for coupling the algal-bacterial treatment process with bioenergy production. The present chapter shall systematically cover the various aspects related to utilization of algal-bacterial interaction in wastewater remediation from laboratory-scale to pilot-scale studies.
Lysimeter experiments were conducted under greenhouse conditions to investigate canola (Brassica napus L.) plant water use, growth, and yield parameters for three different water table depths of 30, 60, and 90 cm. Additionally, control experiments were conducted, and only irrigation was applied to these lysimeters without water table limitations. The canola plant’s tolerance level to shallow groundwater was determined. Results showed that groundwater contributions to canola plant for the treatments at 30, 60, and 90 cm water table depths were 97%, 71%, and 68%, respectively, while the average grain yields of canola were 4.5, 5.3, and 6.3 gr, respectively. These results demonstrate that a 90 cm water table depth is the optimum depth for canola plants to produce a high yield with the least amount of water utilization.
Over the past 20 years, marketplace demand for corn has prompted many farmers in the Red River Valley (RRV) of the north to include more corn in their crop rotations. With a very flat topography and heavy clayey soils, the RRV can have shallow water tables in the spring and fall but can be dry in the summer. Due to these field conditions, some farmers have installed subsurface drainage (SD) systems with structures for controlled drainage (CD, manage the water table in a field) and subirrigation (SI, add water to the field via the SD system) to improve corn production. In a CD + SI field, an eddy covariance system was used to measure and quantify energy flux components along with soil moisture content (SWC) and water table depth (WTD) measurements during four corn growing seasons in 2012, 2013, 2016 and 2017. The results show that the average SWC in 2012 was significantly different from the other three years. The SWC and WTD in 2016 were more stable compared to the other years. The CD practice had a positive effect during a wet year in 2013, which resulted in 26.7% higher yield than the county average. During the dry growing season of 2017, the use of subirrigation resulted in 6.6% higher yield than the county average. The corn evapotranspiration totals (ETa) were 468, 476, 551, and 537 mm for 2012, 2013, 2016, and 2017 growing seasons, respectively. The average crop coefficients were 0.49, 0.73, 0.88, 0.86, and 0.69 for the initial, development, tasseling, reproductive, and maturity stages, respectively. They were calculated from the daily ETa, values only from days with more than 45% of total available water in the root zone, and the ASCE-EWRI standardized grass-based reference evapotranspiration. This study showed that the SD along with the CD + SI system can be used for optimal water management of field corn during both wet and dry years.
Water table contribution to plant water use is a significant element in improving water use efficiency (WUE) for agricultural water management. In this study, lysimeter experiments were conducted in a controlled greenhouse environment to investigate the response of soybean water uptake and growth parameters under four different water table depths (WTD) (30, 50, 70, and 90 cm). Soybean crop water use, WUE, and root distribution under the different WTD were examined. For 30, 50, 70, and 90 cm of WTD treatments, the average water table contributions were 89, 83, 79, and 72%; the grain yields were 15.1, 10.5, 14.1, and 17.2 g/lys.; and the WUEs were 0.22, 0.18, 0.25, and 0.31 g/lys./cm, respectively. Further analysis of the root mass and proportional distribution among the different soil layers illustrated that the lysimeters with 70 and 90 cm WTD had greater root mass with higher root distribution at 40-75 cm of the soil layer. The results indicated that 70 and 90 cm of constant WTD can yield higher grain yield and biomasses with greater WUE and better root distribution than the irrigated or shallow WTD treatments.
Subsurface drainage is an essential practice for farmlands with shallow water table. An accurately designed subsurface drainage system can improve soil and water environment as well as the crop yield. Computer models, such as DRAINMOD, are often used to simulate the field hydrology or design the subsurface drainage systems under different scenarios. The accuracy of the model simulation is highly depending on the accuracy of the input parameters. As an important input parameter to DRAINMOD, evapotranspiration (ET) is estimated using temperature based reference ET method and a stress adjustment factor, while an inaccurate ET estimation can cause errors in DRAINMOD simulation. This paper will evaluate the effects of accurate ET estimation on DRAINMOD prediction through comparisons of various reference ET and actual ET estimates. Reference ET was calculated using data from a nearby weather station. Actual ET was measured by an eddy covariance system. Drainage and hydrology data, including water table, precipitation, and drainage flow were measured in the field in 2009 and used in DRAINMOD simulation. With different reference ET values, different monthly adjustment factors were obtained for each reference ET method in order to match the simulated with the measured water tables. After compared with the actual ET by the eddy covariance method, we found that without adjustment factors, Jensen-Haise, modified Penman (NDAWN) and ASCE-EWRI reference ET methods showed the best agreement than Thorthwaite with an R 2 of 0.63, 0.58, and 0.58, respectively. The default reference ET method showed poor agreement without adjustment factors with an R 2 of 0.05 and 0.10 for B1 and B2 locations, and improved to 0.8 and 0.70 by using adjustment factors.