Wind Drift Evaporation Loss and Soil Moisture Distribution under Sprinkler Irrigated Blackgram (Vigna mungo L.)

An experiment was conducted during March–June 2018 with the sprinkler irrigation system covered in an area of 39×42 m2. Proper design and management of sprinkler irrigation systems improves the uniformity of moisture distribution and reduces wind drift and evaporation losses (WDEL) for effective crop growth. Uniformity coefficient, wind drift and evaporation loss of the sprinkler system at a different pressure head of 2 kg cm-2, 2.5 kg cm-2 and 3 kg cm-2 were studied. Wind speed was observed by using handheld anemometer. The wind speed ranged between 0.9 to 4.5 m s-1. The highest uniformity coefficient of 88.19% and wind drift and evaporation loss of 3.5% were obtained at the pressure head of 3 kg cm-2 and the wind speed of 0.9 m s-1. Soil samples were collected at different depths of 0–10 cm, 10–20 cm, 20–30 cm and at a radial distance from 0 m, 3 m, 6 m, 9 m, 12 m respectively to determine the soil moisture distribution pattern. The soil moisture content values were plotted by using the computer software, surfer 10 of the windows version and contour maps were drawn. The moisture content was found to be more at 0–10 cm depth, as compared to 10–20 cm and 20–30 cm depth. The percentage of moisture was found to be highest at a 6 m distance, which was due to overlapping of the sprinkler system.

Assessing the feasibility of a directional CRNS-sensor for estimating soil moisture

Cosmic Ray Neutron Sensing (CRNS) is a non-invasive tool for measuring hydrogen pools like soil moisture, snow, or vegetation. The intrinsic integration over a radial hectare-scale footprint is a clear advantage for averaging out small-scale heterogeneity, but on the other hand the data may become hard to interpret in complex terrain with patchy land use. This study presents a directional shielding approach to block neutrons from certain directions and explores its potential to gain a sharper view on the surrounding soil moisture distribution. Using the Mont-Carlo code URANOS, we modelled the effect of additional polyethylene shields on the horizontal field of view and assessed its impact on the epithermal count rate, propagated uncertainties, and aggregation time. The results demonstrate that directional CRNS measurements are strongly dominated by isotropic neutron transport, which dilutes the signal of the targeted direction especially from the far field. For typical count rates of customary CRNS stations, directional shielding of halfspaces could not lead to acceptable precision at a daily time resolution. However, the mere statistical distinction of two rates should be feasible.

Study of the Wet Bulb in Stratified Soils (Sand-Covered Soil) in Intensive Greenhouse Agriculture under Drip Irrigation by Calibrating the Hydrus-3D Model

The development of the wet bulb under drip irrigation in sand-covered soils presents a different behavior compared to the one observed in homogeneous soils. Moreover, the presence of a very active crop imposes a series of variations that have not been fully characterized. The aim of this work is to present the data acquisition methodology to calibrate and validate the Hydrus-3D model in order to safely define the evolution of moisture in wet bulbs generated in stratified “sanded” soils characteristic of greenhouses with intensive pepper crop under drip irrigation. The procedure for collecting and processing moisture data in stratified soils has been defined. Soil permeability; retention curve, texture, and bulk density have been measured experimentally for each material. It has been found that the inclusion of a previous day in the simulation improves model predictions of soil moisture distribution. In soils with less gravel, a lower average stress and a more homogeneous moisture distribution were observed. It has been proved that the Hydrus-3D model can reproduce the behavior of sand covered soils under intensive greenhouse growing conditions, and it has been possible to verify that the predictions are adequate to what has been observed in the field. In view of the results, the Hydrus-3D model could be used to establish future irrigation strategies or to locate the optimal placement point of tensiometers that control irrigation in sandy soils for intensive agriculture.

On Change of Soil Moisture Distribution With Vegetation Reconstruction in Mu Us Sandy Land of China, With Newly Designed Lysimeter

BackgroundChina’s so-called Three North Shelterbelt Program (3NSP) has produced a vast area of lined forest reconstruction in the semi-arid regions. This study uses the lined rain-fed Pinus sylvestris var. mongolica (PSM) sand-fixing forest in the eastern part of Mu Us Sandy Land in Northwestern China as an example to investigate the ecohydrological process in this region. Rain gauges, newly designed lysimeters and soil moisture sensors are used to monitor precipitation, deep soil recharge (DSR) and soil water content, where DSR specifically refers to recharge that can reach a depth more than 200 cm and eventually replenish the underneath groundwater reservoir.ResultsThis study shows that there are two obvious moisture recharge processes in an annual base for the PSM forest soil: a snowmelt-related recharge process in the spring and a precipitation-related recharge process in the summer. The recharge depth of the first process can reach 180 cm without DSR occurring (in 2018). The second process results in noticeable DSR in 2018. Specifically, the DSR values over 2016–2018 are 1, 0.2, and 1.2 mm, respectively. To reach the recharge depths of 20, 40, 80, 120, 160, and 200 cm, the required precipitation intensities have to be 2.6, 3.2, 3.4, 8.2, 8.2, and 13.2 mm/d, respectively. The annual evapotranspiration in the PSM forest is 466.94 mm in 2016, 324.60 mm in 2017, and 183.85 mm in 2018.ConclusionThis study concludes that under the current precipitation conditions (including both dry- and wet-years such as 2016–2018), water consumption of PSM somewhat equals to the precipitation amount, and PSM has evolved over years to regulate its evapotranspiration in response to annual precipitation fluctuations in Mu Us Sandy Land of China.