Using soil surface temperature to assess soil evaporation in a drip irrigated vineyard
Evaporation from the soil is an important part of the water balance of a crop, when considering water use efficiency. In this paper, a non-intensive method is tested to estimate relative soil evaporation, which is based upon a linear function of soil surface temperature change between a saturated and drying soil. The relative evaporation (RE) method of Ben-Asher et al. (1983) was calibrated using microlysimeters and thermal imaging. Soil surface temperature in a drip irrigated vineyard was then collected using infrared temperature sensors mounted on a quad bike, on several days of the 2009-2010 season. Soil surface temperature in the vineyard ranged from 4.6 °C to 65.5 °C undervine and 6.8 °C to 75.6 °C in the middle of the row. The difference between daily minima and maxima of soil surface temperature ranged from 20.2 °C to 59.7 °C in the inter-row and 13.6 °C to 36.4 °C undervine. Relative evaporation averaged 54% of evaporation from a saturated soil in the inter-row and 97% undervine. Based upon the calculation of RE, the average daily amount of soil evaporation undervine was between 0.64 mm and 1.83 mm, and between 0.69 mm and 2.52 mm inter-row. The soil evaporation undervine and inter-row both exhibited spatial variability across the vineyard, however the undervine area had less spatial variability compared to the inter-row area.
Estimation of soil evaporation in an irrigated vineyard from soil surface temperature
Soil evaporation is a significant unproductive loss of water that needs to be and can be managed in irrigated systems. A method is used to estimate soil evaporation based upon soil surface temperature change between a saturated and drying soil. The relative evaporation (RE) method of Ben-Asher et al. (1983) was deployed. Soil surface temperature in a drip irrigated vineyard was collected using infra-red temperature sensors. Average daily soil evaporation under-vine was between 0.6mm and 1.8mm and between 0.7mm and 2.5mm for the inter-row. Evaporation from the soil is an important part of the water balance of a crop (Burt et al. 2005). Previous estimates vary widely, from 30-65% of evapotranspiration (Kerridge et al 2008a). The Ben-Asher et al. (1983) method allows potential soil evaporation to be estimated from the daily latent fluxes of a saturated, steady-state dry and a drying soil. By calculating a relative evaporation (RE) factor and multiplying it by an estimate of potential evaporation, determined for example by the FAO-56 procedure (Allen et al., 1998), an estimate of soil evaporation may be made. The main benefit of this method is that it allows rapid and simultaneous estimates of evaporative flux to be measured at numerous sites under study. This can then be linked with methods for spatial estimation of plant water use and stress (Hornbuckle et al., 2008b).
Analytical Solution for Drainflows from Bilevel Multiple-Drain Subsurface Drainage Systems
Waterlogging and soil salinisation is widespread in the semiarid, irrigated areas of the world. Subsurface drainage is a useful tool in reducing these effects on crops; however, there has been negative downstream effects of drainage in the salt loads discharged to rivers, lakes, and wetlands. Thus, subsurface drainage in semiarid, irrigated areas needs to balance the demands of providing adequate waterlogging and salinity control while minimizing salt loads. Bilevel drainage, in which shallow drains are placed between deeper drains, is a potential method to meet this required balance. This paper describes the development of an analytical solution to this design approach. A previous potential theory was extended to incorporate multiple series of shallow drains placed between two deep drains. The analytical solution was then applied using the Mathematica software to provide useful information on flow rates and flow lines with varying configurations of deep and shallow drains. The theory was then used to compare spacing and drain flow characteristics between a drainage system with only deep drains and multilevel systems that combine shallow drains with deep drains. A large number of possible configurations of shallow drains between deeper drains exist. For ease of comparison, the concept of "drainage equivalence" was developed, representing the drainage discharge per unit spacing between drains. The analytical solution for bilevel drainage situations with single and multiple shallow drains between deeper drains showed that for equivalent rates of total drainage, spacing between deep drains could be increased significantly by the use of shallow drains. It also demonstrated that flow paths and drainage rates from shallow and deep drains and the total system drainage could be altered significantly by altering the number of shallow drains. This information should be useful when considering various drainage configurations to meet the dual objectives of root zone salinity control and minimization of drainage salt loads.
Water requirements for earthworms 'Eisenia andrei' grown exclusively on broiler litter
The use of vermiculture to value-add to broiler litter (BL) has been seen as problematic due to the high levels of uric acid and salts in poultry manure. Results from this experiment indicate that these issues can be overcome with frequent watering over the first 8 days of the system's operation. The conversion of BL into vermicast was maximised with twice daily applications of 100 and 200ml of water. These frequent water applications also led to average total mortality being lower and healthier earthworms.