Linear Relationship of a Soil Total Water Potential Function and Relative Yield—A Technique to Control Salinity and Water Stress on Golf Courses and Other Irrigated Fields

A simple empirical approach is proposed for the determination of crop relative yield (%) through the soil total water potential (kPa). Recurring to decimal logarithms, from analytical exponential expressions, a linear simple relationship of soil total water potential Ψt (matric Ψm + potential Ψo) function and crop relative yield was studied and developed. The combination of the salinity model, the soil water retention model and the matric potential approach were used to reach this objective. The representation of turfgrass crop relative yield (%) versus a function of soil total water potential f(Ψt) values was shown through a log-normal graph (y = a + mx); the log scale axis “y” (ordinates) defines relative yield Yr, being two the origin ordinate “a” and “m” the slope; the normal decimal scale axis “x” (abscissa) is the function of soil total water potential f(Ψt). Hence, it is possible, using only two experimental points, to define a simple linear relation between a function of soil total water potential and crop relative yield, for a soil matric potential value lower than −20 kPa. This approach was first tested on golf courses (perennial turfgrass fields), but it was further decided to extend it to other annual crop fields, focused on the model generalization. The experimental plots were established, respectively, in Algarve, Alentejo and Oeiras (Portugal) and in the North Negev (Israel). Sprinkler and trickle irrigation systems, under randomized blocks and/or water and salt gradient techniques, were used for water application with a precise irrigation water and salt distribution. Results indicated that there is a high agreement between the experimental and the prediction values (R2 = 0.92). Moreover, the precision of this very simple and easy tool applied to turfgrass fields and other irrigated soils, including their crop yields, under several different sites and climatic conditions, can contribute to its generalization.

Productivity and water use efficiency of kinnow mandarin (citrus reticulate blanco) as influenced by drip trickle irrigation and hydrogel

An experiment was conducted to find out the effect of drip trickle irrigation and hydrogel with black polyethylene mulch on productivity and water use efficiency of Kinnow mandarin. The two years pooled data revealed that highest available nitrogen, phosphorus and potassium (244, 20 and 164 kgha-1), porosity and maximum water holding capacity (34.5 and 40.9 %) and percent increase height, spread and canopy volume (13.6, 14.8 and 44.5 %), respectively, were obtained with the application of 3 days drip trickle irrigation and 90 g hydrogel with black polyethylene mulch materials of tree. The drip trickle irrigation and hydrogel with black polyethylene mulch produced a significantly (p=0.05) maximum improve in soil moisture content over control treatment. The 3 days drip trickle irrigation and 90 g hydrogel with mulch showed highest fruit yield (9404.7 kg ha-1), length (6.5 cm), weight (116.5 g) and quality of fruit volume (113.9 cc), Juice content (54.1 %) and TSS (13.3 0Brix). The specific gravity and titratable acidity showed reverse trend. The water use efficiency and benefit cost ratio were better in 3 days drip trickle irrigation and 90 g hydrogel with mulch materials of tree.

Nitrate distribution pattern under conventional and trickle irrigation system

Nitrate is a highly mobile ions that moves with water. So that nitrate distribution around the driplines is strongly affected by irrigation and fertigation strategy. Nitrate movement under conventional flood irrigation system was observed 2 to 3.5 times faster as compared with trickle irrigation as well as NO3 "-N concentrations exceeded the threshold limit (i.e. 10 mg l-1) under traditional irrigation method, while stayed below the threshold limit under micro irrigation methods. Nitrate distribution was influenced by hydraulic properties, drip discharge rate, soil layering, timing of nutrient application and irrigation frequency. To maintain larger amounts of nutrient nearby emitter in highly permeable coarse-textured soils, nutrients must be applied at the starting of an irrigation cycle so that it is less susceptible to leaching losses. Study revealed that higher transpiration raised the NO3-N uptake by the plats. The study also revealed that urea moves promptly with irrigation water and urea–ammonium–nitrate fertilizer increased the nitrate concentration, near the drip line immediately after the drip fertigation due to the nitrification, while low concentrations was found near the periphery of the wetting zone.

Management of trickle irrigation for banana: Hydrodynamic processes and sensor placement at the root zone

ABSTRACT Information on soil hydrodynamic processes assists in explaining the soil-water-plant relationship and has practical applications to irrigation management, such as the definition of soil water sensor placement. The objective of this study was to detail the hydrodynamic process in the soil root zone and to define the location for placement of soil water sensor under different configurations of trickle irrigation in banana crops. Three micro-sprinkler emitters with flow rates of 70 (T1), 53 (T2), 35 L h-1 (T3), and two drip system, one with one drip line per row of plants (T4), and another with two drip lines per row of plants (T5) were evaluated. The experiment was conducted in a randomized block design with five repetitions. Higher water extraction was found for irrigation systems with higher flow rates for all configurations of trickle irrigation systems. Soil moisture sensors in drip systems should be placed at distances of 0.75 to 0.81 m from the pseudo stem and at depths of 0.33 to 0.44 m. Under micro-sprinkler systems, soil water sensors should be placed at 0.75, 0.77 and 0.83 m from the pseudo stem towards to the emitter and at depths of 0.33, 0.48 and 0.55 m for emitter flow rates of 35, 53 and 70 L h-1, respectively.

Numerical Simulation of Water Distribution with Uptake Root in Drip Irrigation using Different Soil Hydraulic Models

Surface drip irrigation is one of the most conservative irrigation techniques that help control providing water directly on the soil through the emitters. It can supply fertilizer and providing water directly to plant roots by drippers. One of the essential needs for trickle irrigation nowadays is to obtain more knowledge about the moisture pattern under the trickling source for various types of soil with various discharge levels with trickle irrigation. Simulation numerical using HYDRUS-2D software, version 2.04 was used to estimate an equation for the wetted area from a single surface drip irrigation in unsaturated soil is taking into account water uptake by roots. In this paper, using two soil types were used, namely sandy loam and clay loam, with three types of plants; (corn, tomato, and sweet sorghum). The soil wetting pattern was analyzed each half an hour for three hours of irrigation time and three initial soil moisture content. Equations for wetted radius and wetted depth were predicted and evaluated by utilizing the statistical parameters for the different hydraulic soil models (Model Efficiency (EF) and Root Mean Squares Error (RMSE)). The values RMSE does not exceed 0.40 cm, and EF is greater than 0.96 for all types of soil. These values were between the values obtained from program HYDRUS-2D and the values obtained from formulas. This shows that evolved formula can be utilized to describe the soil wetting pattern from the surface drip irrigation system. The relative error for the different hydraulic soil models was calculated and compared with Brooks and Corey's model, 1964. There was good agreement compared with different models. RMSE was 0.23 cm, while the relative error -1% and 1 for EF for wetted radius.