Mapping Daily Evapotranspiration at Field Scale Using the Harmonized Landsat and Sentinel-2 Dataset, with Sharpened VIIRS as a Sentinel-2 Thermal Proxy

Accurate and frequent monitoring of evapotranspiration (ET) at sub-field scales can provide valuable information for agricultural water management, quantifying crop water use and stress toward the goal of increasing crop water use efficiency and production. Using land-surface temperature (LST) data retrieved from Landsat thermal infrared (TIR) imagery, along with surface reflectance data describing albedo and vegetation cover fraction, surface energy balance models can generate ET maps down to a 30 m spatial resolution. However, the temporal sampling by such maps can be limited by the relatively infrequent revisit period of Landsat data (8 days for combined Landsats 7 and 8), especially in cloudy areas experiencing rapid changes in moisture status. The Sentinel-2 (S2) satellites, as a good complement to the Landsat system, provide surface reflectance data at 10–20 m spatial resolution and 5 day revisit period but do not have a thermal sensor. On the other hand, the Visible Infrared Imaging Radiometer Suite (VIIRS) provides TIR data on a near-daily basis with 375 m resolution, which can be refined through thermal sharpening using S2 reflectances. This study assesses the utility of augmenting the Harmonized Landsat and Sentinel-2 (HLS) dataset with S2-sharpened VIIRS as a thermal proxy source on S2 overpass days, enabling 30 m ET mapping at a potential combined frequency of 2–3 days (including Landsat). The value added by including VIIRS-S2 is assessed both retrospectively and operationally in comparison with flux tower observations collected from several U.S. agricultural sites covering a range of crop types. In particular, we evaluate the performance of VIIRS-S2 ET estimates as a function of VIIRS view angle and cloud masking approach. VIIRS-S2 ET retrievals (MAE of 0.49 mm d−1 against observations) generally show comparable accuracy to Landsat ET (0.45 mm d−1) on days of commensurate overpass, but with decreasing performance at large VIIRS view angles. Low-quality VIIRS-S2 ET retrievals linked to imperfect VIIRS/S2 cloud masking are also discussed, and caution is required when applying such data for generating ET timeseries. Fused daily ET time series benefited during the peak growing season from the improved multi-source temporal sampling afforded by VIIRS-S2, particularly in cloudy regions and over surfaces with rapidly changing vegetation conditions, and value added for real-time monitoring applications is discussed. This work demonstrates the utility and feasibility of augmenting the HLS dataset with sharpened VIIRS TIR imagery on S2 overpass dates for generating high spatiotemporal resolution ET products.

Reducing the Evaporative Demand Improves Photosynthesis and Water Use Efficiency of Indoor Cultivated Lettuce

Currently, climate change is affecting considerably the availability of freshwater for agriculture, increasing the need for the optimization of crop water use efficiency. Attempts to use VPD (vapor pressure deficit) modulation to reduce water consumption have been made. However, the effects of VPD on leaf stomatal and hydraulic traits, and on possible tradeoffs between photosynthetic carbon gain and transpiration, are rarely reported. We analyzed photosynthesis (gas-exchange, photochemistry) stomatal and hydraulic-related traits of green (G) and red (R) butterhead lettuce (Lactuca sativa L.) grown under low and high VPD (LV, HV) in a controlled environment. Our results showed that plants developed a higher number of small stomata under LV, allowing better regulation over opening/closing mechanisms and thus increasing net photosynthesis by 18%. LV plants also achieved better performance of the photosystem II and a more efficient water use (increments in ΦPSII and iWUE by 3% and 49%), resulting in enhanced plant growth and reduced need for irrigation. Significant differences between G and R plants were limited to a few traits, and the physiological response under the two VPDs did not show cultivar-specific response. We discuss the role of VPD management as necessary to maximize crop water use by harmonizing photosynthesis and transpiration.

Effect of decision variables on yield and water productivity of onion under conventional furrow irrigation system in bako woreda, Ethiopia

Flow rate and furrow length are the main irrigation decision variables currently affecting yield and water productivity at farm level. Improper selection of these variables produces an over use of water and loss in crop production. The general objective was to investigate the effect of decision variables on yield and water productivity of onion under conventional furrow irrigation system, with specific objective to analyze the effect of flow rate, furrow length and their interaction on yield and water productivity of onion. The field experiment was laid out in randomized complete block design with factorial arrangement of three levels of flow rate (0.7, 0.98 and 1.3 L/S) and three levels of furrow length (25, 35 and 50 m) with three replications. Inflow out flow method was used to determine the infiltration characteristics of the soil and Irrigation depth was controlled by using 3-inch Parshall flume. The maximum non-erosive flow rate to the experimental site was fixed through design equation considering soil textural class and furrow bed slope. Effect of furrow length and flow rate on yield and water productivity of the onion were used for evaluation. Their analyses indicated that effect of furrow length and their interaction with flow rate on yield were not significant (p<0.05). However, the flow rate showed highly significant (p<0.01) effect on yield of onion. The ranges of mean yield gained from furrow length and flow rate were F1 (14.75 ton ha-1) to F3 (15.96 ton ha-1) and Q1 (13.59 ton ha-1) to Q3 (19.69 ton ha-1), respectively. The effect of furrow length on crop water use efficiency and field water use efficiency was not significant (p<0.05). However, the flow rate has showed highly significant (p<0.01) effect on crop water use efficiency and field water use efficiency. The range of mean crop water use efficiency and field water use efficiency from furrow length and flow rate were F1 (33.65 kg/ha/mm) to F3 (36.41 kg/ha/mm) and Q1 (30.99 kg/ha/mm) to Q3 (38.65kg/ha/mm) and F1 (2.06 kg/m3) to F3 (2.23 kg/m3) and Q1 (1.89 kg/m3) to Q3 (2.36 kg/m3), respectively. Therefore, it can be concluded that a furrow length of 50 m is suitable to use 1.3 L/S of flow rate for better onion yield and water productivity under similar soil type of study area. Int. J. Agril. Res. Innov. Tech. 11(1): 92-100, June 2021

Role of Raised Bed Technique on Water Productivity and Wheat and under the conditions of irrigated agriculture in central Iraq

"A field experiment was conducted during the agricultural season of 2017-2018 in the site is located at 82"" 10' 33ᵒ North, and longitude 51"" 32' 44ᵒ , East at an altitude of 33m above sea level. In order to evaluate the productivity of irrigation water by method of cultivation on irrigated furrows, when growing crops of wheat. Two factors were experienced in the cultivation of wheat, The first factor is the method of cultivation of five treatments were used included: Treatment of the cultivation of wheat in basins (B), treatment of the cultivation of wheat on bed with 50 cm width (S1), 60cm (S2), 70cm (S3) and 80cm (S4), The second factor is irrigation levels depletion included: 40, 60 and 80% of available water coded as W1, W2 and W3, respectively,. The results were as follows: Actual water consumption values for basin and bed treatments reached 389, 384, 365, 369.20, 367and 341mm for treatment BW1, BW2, BW3,SW1, SW2 and SW3 respectively. Treatment of wheat crops on bed with 80 cm width gave the highest average field water use efficiency reached 6.84 kg m-3 while BW3 treatment gave lowest average field water use efficiency reached 1.47 kg m-3. The highest average crop water use efficiency were found in S4W1ٚ S4W2 reached 2.06 and 2.07 kg m-3, respectively, It was lowest value for crop water use efficiency at BW3 reached 1.06 kg m-3. The percentage increase in the average efficiency of crop water using for bed treatments 40.37, 57.80, 73.39 and 85.32% for treatments S1, S2, S3 and S4 respectively Compared with basin treatment (B).The highest average total grains yield for Treatment of wheat crops on bed with 80 cm width was 7253kg ha-1 , Irrigation levels also affected the total grains yield, irrigation treatment of depletion 40% gave highest average 6300 kg ha-1 , That did not differ significantly from the irrigation treatments of depletion 60% In which the total grain yield was reached 6228 kg ha-1 ,In the interference factors between the cultivation method and the irrigation levels, the interference factors excelled S4W1, S3W2 and S4W2 Without significant differences in the total yield average 7600,7310 and 7600 kg ha-1, Respectively"

CubeSats deliver daily crop water use at 3 m resolution

&lt;p&gt;Precision agriculture needs accurate information on crop water use (via evaporation) at high spatiotemporal resolutions. Conventional satellite missions have traditionally required a compromise between having high spatial resolution retrievals occasionally; or coarse resolution captures regularly. The development of CubeSats is relaxing the need for such a compromise by monitoring the Earth at high spatiotemporal resolutions. Here, we show the results of using Planet&amp;#8217;s daily CubeSat imagery to derive evaporation at 3 m spatial resolution over three agricultural fields in Nebraska USA. Our results indicate that the derived evaporation estimates can provide accurate information on crop water use when evaluated against eddy covariance measurements (r&lt;sup&gt;2&lt;/sup&gt; of 0.86-0.89; mean absolute error between 0.06-0.08&lt;sup&gt;&lt;/sup&gt;mm/h) and deliver new insights to enhance water security efforts and in-field decision making.&lt;/p&gt;