Quantifying irrigation water use with remote sensing: Soil water deficit modelling with uncertain soil parameters

AbstractIrrigation is an important adaptation to reduce crop yield loss due to water stress from both soil water deficit (low soil moisture) and atmospheric aridity (high vapor pressure deficit, VPD). Traditionally, irrigation has primarily focused on soil water deficit. Observational evidence demonstrates that stomatal conductance is co-regulated by soil moisture and VPD from water supply and demand aspects. Here we use a validated hydraulically-driven ecosystem model to reproduce the co-regulation pattern. Specifically, we propose a plant-centric irrigation scheme considering water supply-demand dynamics (SDD), and compare it with soil-moisture-based irrigation scheme (management allowable depletion, MAD) for continuous maize cropping systems in Nebraska, United States. We find that, under current climate conditions, the plant-centric SDD irrigation scheme combining soil moisture and VPD, could significantly reduce irrigation water use (−24.0%) while maintaining crop yields, and increase economic profits (+11.2%) and irrigation water productivity (+25.2%) compared with MAD, thus SDD could significantly improve water sustainability.

SummaryIn each of the years from September 1977 to July 1982 winter wheat was grown on one or more of three clay soil sites (clay content 35–55%) in Oxfordshire where the climate is close to the average for the area of England growing winter cereals.The effects on crop water use of different soil management practices, including ploughing, direct drilling and subsoil drainage, are compared. Cultivation treatment had little effect on the maximum depth of water extraction, which on average in these clay soils was 1·54 m below the soil surface. Maximum soil water deficit was also little affected by cultivation; the maximum recorded value was 186±7·6 mm. Subsoil drainage increased the maximum depth of water extraction by approximately 15 cm and the maximum soil water deficit by about 17 mm.Generally soil management had little effect on either total water use by the crop which was found to be close to the potential evaporation estimated by the method of Penman, or water use efficiency which for these crops was about 52 kg/ha par mm water used.Results are discussed in relation to limitations to potential yield.

SummaryAutomatic mobile shelters were used to keep rain off a barley crop in a drought experiment. The treatments ranged from no water during the growing season to regular weekly irrigation. This paper reports the effect of drought on the harvest yield and its components, on water use and nutrient uptake.Drought caused large decreases in yield, and affected each component of the grain yield. The magnitude of each component varied by up to 25% between treatments, and much of the variation could be accounted for by linear regression against the mean soil water deficit in one of three periods. For the number of grains per ear, the relevant period included tillering and ear formation; for the number of ears per unit ground area, the period included stem extension and tiller death; for grain mass, the period included grain filling.The harvest yields were linearly related to water use, with no indication of a critical period of drought sensitivity. The relation of grain yield to the maximum potential soil water deficit did show that a prolonged early drought had an exceptionally large effect on both yield and water use.Two unsheltered irrigation experiments, also on barley, were made in the same year on a nearby site. The effects of drought on yield in these experiments were in good agreement with the effects observed on the mobile shelter site.When fully irrigated, the small plots under the mobile shelters used water 11% faster than larger areas of crop, because of advection. The maximum depth from which water was extracted was unaffected by the drought treatment. When 50% of the available soil water had been used the uptake rate decreased, but the maximum depth of uptake continued to increase.Measurements of crop nutrients at harvest showed that nitrogen uptake was large, because of site history, and that phosphate uptake was decreased by drought to such an extent that phosphate shortage may have limited yield.

ABSTRACT Crop strategies focused on the rational use of water are required in semiarid regions. Thus, the objective of this work was to evaluate the physiological quality of maize seeds produced under soil water deficit conditions. Five irrigation water depth were established, based on the field capacity (100, 85, 70, 55 and 40%), to control the available water for two maize hybrids (2B-587 and DKB-390). A randomized block design was used, with a split-plot arrangement and four repetitions. The plots consisted of irrigation water depths, and the subplots consisted of maize hybrids. The seed water concentration, germination, and vigor were determined after the harvest, using data from first germination counting, seedling emergence, germination speed index, seedling length, and accelerated aging, electrical conductivity, and modified cold tests. The maize hybrid DKB-390 showed better physiological potential under the soil water deficit conditions evaluated. The irrigation water depths lower than 70% of field capacity resulted in decreases in soil water contents and affected negatively the physiological quality of the maize seeds produced.

Irrigation water use (IWU) or withdrawal is a key component for the water management of a region since it tends to exceed the crops consumptive water use, especially in water-stressed regions where groundwater is the main source of water. Nevertheless, temporal IWU information is missing in many irrigation areas. Remote sensing (RS) data is commonly used for crop water requirements estimations in areas with lack of data, however, IWU is more complex to approach since it also depends on water use efficiency, irrigation system type, irrigation scheduling, and water availability, among others. This work explores the use of remote sensing data (TRMM, MODIS) and land surface hydrological products (GLDAS 2 and MERRA 2) to obtain insights about the space-time annual IWU patterns across croplands located within Mexico’s northeast region. Reported IWU in three irrigation districts (Don Martín, Región Lagunera and Bajo Río Bravo) was used to obtain a functional model using satellite data derived. Results suggest strong relationship between reported IWU with soil moisture content from GLDAS and the maximum annual EVI from MODIS, where a potential regression shown statistical correlations of 0.83 and 0.77, respectively.

HighlightsAn Irrigation Scheduling Supervisory Control and Data Acquisition (ISSCADA) system was tested against a soil electrical conductivity (EC) based method for variable-rate irrigation (VRI).Soil EC was used to create irrigation prescription in EC-based VRI.ISSCADA generated VRI prescriptions using canopy temperature, soil water content, and weather data.ISSCADA-based VRI reduced irrigation water use and increased irrigation water productivity.Abstract. Use of variable-rate irrigation (VRI) technology has the potential to improve irrigation water use efficiency (IWUE). VRI hardware is commercially available and can be implemented in any center pivot or lateral move irrigation system. However, practical methods and algorithms for creating VRI prescriptions have become the bottleneck in accelerating the adoption of VRI. An Irrigation Scheduling Supervisory Control and Data Acquisition (ISSCADA) system for VRI was evaluated for two years in a humid region in the Mississippi Delta. The ISSCADA system was used to manage irrigation of soybeans for two seasons. In field practice, the ISSCADA system scanned the field for canopy temperature and collected soil water data from time domain reflectometers and weather data from a nearby weather station. The ISSCADA system automatically generated VRI prescription maps. The maps were modified to include plots managed using soil electrical conductivity (EC) based VRI prescriptions. Test results indicated that there was no difference in crop yield between EC-based VRI and ISSCADA-based VRI management. However, ISSCADA-based VRI management reduced irrigation water use and increased irrigation water productivity in comparison with EC-based VRI. There is great potential for the use of ISSCADA for VRI in humid regions. Keywords: Canopy temperature, Soil electrical conductivity, Soil moisture sensor, Soil water sensor, Soybean, Variable rate irrigation.

The study examined the dynamic nature of water balance parameters over Kano town, a semi-arid environment and impact of Linacre derived potential evapotranspiration method on the supplementary irrigation water needs of selected crops. Monthly Rainfall and Temperature data were collected from the Nigerian Meteorological Agency, Lagos for the period 1953-2012. The study observed that there is a steady decline in annual precipitation over Kano from the first decade (1953-1962) to the fifth decade (1993-2002), after which there was a sign of weak recovery in the last decade (2003-2012). For water loss through potential evapotranspiration, there was a steady rise from the first decade (1953-1962) to the fifth decade (1993-2002), and then followed by a sudden decline in the last decade (2003-2012). The total average of water storage on the other hand, first experienced a rise between the first two decades (1953-1962) and (1963-1972), followed by a steady decline, up until the fifth decade (1993-2002) and finally a rise in the last decade (20032012). The total average of soil water deficit experienced a steady rise between the first and the fifth decades (1953-1962) to (1993-2002), this was followed by a decline in the last decade (20032012). Finally, the total average of water surplus experienced a steady decline between the first and the fifth decades. The observed decline in precipitation, storage, and water surplus, and the rise in water loss from potential evapotranspiration and soil water deficit, suggests that there have been changes in the climatic pattern over Kano and this could be seen in the supplementary irrigation water needs of Tomato/Cabbage/Carrot.