Drip / trickle irrigation

Inadequate oxygen concentration in the root zone is a constraint to plant performance particularly in heavy, compacted and/or saline soils. Sub-surface drip irrigation (SDI) offers a means of increasing oxygen to plant roots in such soils, provided irrigation water can be hyper-aerated or oxygenated. Hydrogen peroxide (HP) at the rate of 5 litre ha−1 at the end of each irrigation cycle was injected through SDI tape to a field-grown zucchini (courgette) crop (Cucurbita pepo) on a saturated heavy clay soil in Queensland, Australia. Fruit yield, number and shoot weight increased by 25%, 29% and 24% respectively due to HP treatment compared to the control. Two pot experiments with vegetable soybean (Glycine max) and cotton (Gossypium hirsutum) compared the effectiveness of HP and air injection using a Mazzei air injector (a venturi), throughout the irrigation cycle in raising crop yield in a heavy clay soil kept at saturation or just under field capacity. Fresh pod yield of vegetable soybean increased by 82–96% in aeration treatments compared with the control. The yield increase was associated with more pods per plant and greater mean pod weight. Significantly higher above ground biomass and light interception were evident with aeration, irrespective of soil water treatment. Similarly cotton lint yield increased by 14–28% in aeration treatments compared with the control. The higher lint yield was associated with more squares and bolls per plant which accompanied greater above ground biomass and an increase in root mass, root length and soil respiration. Air injection and HP effected greater water use, but also brought about an enhancement of water use efficiency (WUE) for pod and lint yield, and increased leaf photosynthetic rate in both species but had no effect on transpiration rate and stomatal conductance per unit leaf area. Aeration-induced enhanced root function was arguably responsible for greater fruit set and yield in all three crops, while in vegetable soybean greater canopy cover, radiation interception and total vegetative biomass were responsible for additional yield benefit. Increased aeration of the root zone in heavy clay soils employing either air injection or HP proved beneficial to SDI irrigated crops, irrespective of the soil water conditions, and can add value to grower investments in SDI.

Experiments were conducted in summer of 2003 and 2004 to study the effect of withholding irrigation on tomato growth and yield in a drip irrigated, plasticulture system. Irrigation treatments were initiated at tomato planting (S0), after transplant establishment (S1), at first flower (S2), at first fruit (S3), or at fruit ripening (S4). An additional treatment received only enough water to apply fertigation (FT). Withholding drip irrigation for a short period (S2–S3) increased tomato marketable yield by 8–15%, fruit number by 12–14% while reducing amount of irrigation water by 20% compared to the S0 treatment. Withholding drip irrigation also increased irrigation water use efficiency (IWUE). Similar trends were observed in 2003 and 2004 despite large differences in rainfall, heat units, and tomato yield between years. This suggests that if soil moisture is adequate at transplanting, subsequent withholding of irrigation for 1–2 weeks after tomato transplanting may increase yield while reducing the amount of irrigation water.

Changes in soil sodicity–salinity parameters are one of the most characteristic alterations after treated sewage effluent (TSE) irrigation in agro-systems. Considering the importance of these parameters for agricultural management, as well as the economical value of sugarcane for Brazil, the present study aimed at evaluating effects on soil sodicity and salinity under tropical conditions over 16 months of TSE irrigation in a sugarcane plantation at Lins, São Paulo State, Brazil. Soil samplings were carried out in February 2005 (before planting), December 2005 (after 8 months of TSE irrigation) and September 2006 (after 16 months of TSE irrigation) following a complete block design with four treatments and four replicates. Treatments consisted of: (i) control, without TSE irrigation; (ii) T100, T150 and T200, with TSE irrigation supplying 100% (0% surplus, total of 2524 mm), 150% (50% surplus, total of 3832 mm) and 200% (100% surplus, total of 5092 mm) of crop water demand, respectively. Compared to initial soil conditions, at the end of the experiment increases of exchangeable sodium (from 2.4 to 5.9 mmolc kg−1), exchangeable sodium percentage (ESP) (from 8 to 18%), soluble Na (from 1.4 to 4.7 mmol L−1) and sodium adsorption ratio (SAR) of soil solution (from 3.6 to 12.6 (mmol L−1)0.5) were found in the soil profile (0–100 cm) as an average for the irrigated plots due to high SAR of TSE. Associated with the increments were mostly significant increases in clay dispersion rates at depths 0–10, 10–20 and 20–40 cm. Electrical conductivity (EC) of soil solution increased during the TSE irrigation period whereas at the end of the experiment, after short term discontinuation of irrigation and harvest, EC in the topsoil (0–10 and 10–20 cm) decreased compared to the previous samplings. Moreover, despite increasing sodicity over time mainly insignificant differences within the different irrigated treatments were found in December 2005 and September 2006. This suggests that independent of varying irrigation amounts the increasing soil sodicity over time were rather caused by the continuous use of TSE than by its quantity applied. Moreover, also plant productivity showed no significant differences within the TSE irrigated plots. The study indicates that monitoring as well as remediation of soil after TSE irrigation is required for a sustainable TSE use in order to maintain agricultural quality parameters.

In this paper, we examine the discharge of labyrinth-channel emitters under different operating pressures (P) and water temperatures (T). An artificial neural network (ANN) and multiple linear regression (MLR) model are developed for the emitter flow variation (qvar) and the manufacturer’s coefficient of variation (CV). As well as P and T, the structural parameters of the labyrinth emitter are considered as independent variables. The ANN results demonstrate that a feed-forward back-propagation network with five input neurons and 14 neurons in the hidden layer successfully model qvar and CV. The trapezoidal unit spacing and path length of the labyrinth emitter are found to be insignificant. In our ANN model, we use a hyperbolic tangent as the activation function in the hidden layer and the output layer. Statistical criteria indicate that the ANN is better at predicting the hydraulic performance of the labyrinth emitters than MLR. The root mean square errors for qvar and CV are 1.0497 and 0.0044, respectively, for the ANN model, and 2.0703 and 0.0107, respectively, for the MLR model using a test dataset. The relatively low errors obtained by the ANN approach lead to high model predictability and are feasible for modeling the hydraulic performance of labyrinth emitters.

The effects of water temperature and structural parameters of a labyrinth emitter on drip irrigation hydraulic performance were investigated. The inside structural parameters of the trapezoidal labyrinth emitter include path width (W) and length (L), trapezoidal unit numbers (N), height (H), and spacing (S). Laboratory experiments were conducted using five different types of labyrinth-channel emitters (three non-pressure compensating and two pressure compensating emitters) commonly used for subsurface drip irrigation systems. The water temperature effect on the hydraulic characteristics at various operating pressures was recorded and a comparison was made to identify the most effective structural parameter on emitter performance. The pressure compensating emitter flow exponent (x) average was 0.014, while non-pressure compensating emitter’s values average was 0.456, indicating that the sensitivity of non-pressure compensating emitters to pressure variation is an obvious characteristic (p < 0.001) of this type of emitters. The effects of water temperature on emitter flow rate were insignificant (p > 0.05) at various operating pressures, where the flow rate index values for emitters were around one. The effects of water temperature on manufacturer’s coefficient of variation (CV) values for all emitters were insignificant (p > 0.05). The CV values of the non-pressure compensating emitters were lower than those of pressure compensating emitters. This is typical for most compensating models because they are manufactured with more elements than non-compensating emitters are. The results of regression analysis indicate that N and H are the essential factors (p < 0.001) to affect the hydraulic performance.

Accurate measurements of hydraulic characteristics of flow are needed for design and evaluation of irrigation systems. For measuring flow, flumes are commonly used. is in order to obtain accurate readings for flow measurement, flumes should not be submerged and the upstream flow should not be affected by the downstream flow. This study investigates a proper way to install trapezoidal flumes that can be applied in many ways to measure in flow and outflow discharge in furrow irrigation systems. During sixty field operations, it was discovered that the flume has to be installed at least four centimeters above the bottom of furrow, in addition to the alignment on each side. This is essential for proper functioning of the flume under the conditions of free flow., Measurements made showed that if flume was held four centimeters above the bottom, the percentage of submergence in different depths of water, had met the standard rate (lower than 70% submergence), and hence the percentage of the error in flow measurement was reduced. In order to ensure the free flow in the trapezoidal flume, the large number of field operations showed that the entrance of the flume, which is used to analyze the inflow, has to be installed at a height of four centimeters or more above the bottom of furrow, with the condition that its entrance borders are strengthened. The exit of the flume should also be firmly fixed on the bottom of furrow in order not to impede the passage of flow, with the condition that beneath the flume the furrow bottom should be made deeper in order to create free flow. These recommendations are important, especially in furrow irrigation systems.
By: Dr. Kaveh Ostad-Ali-Askari

Many new studies suggest into the possibility of obtaining positive results when exposing the water to the magnetic field of the particular iceberg, where this lead to change some properties of the water, and that the main objective for the design of systems of drip irrigation is to reduce the losses water that occur as a result of deep penetration or surface runoff. The objective of this research is to study the effect of treatment magnetism on the movement of water and the distribution of moisture in the soil, where this study included a 17 tests using three rates of addition of water (1.8, 2.4, 3.0) cm 3 /min/cm and four intensities of magnetic water treatment (500, 1000, 1500, 2000), in addition to the use of normal salty water and salty water treated magnetically. The results show that the wetting front of water treated magnetically, whether sweet or salty, progressing faster through the soil than the wetting front of normal water (without treatment) at all adding rates of water, where the increasing percent in the size of the wetted area of soil when using the magnetically treated water with intensity of 2000 gauss is 12 % and 18 % and 15.3 % for adding rates 1.8 and 2.4 and 3.0 cm 3 /min /cm , respectively, also, the moisture content of the soil as well as the proliferation and homogeneity was higher in the case of the using magnetically treated water.

The increased use of marginal quality water with drip irrigation requires sound fertigation practices that reconcile environmental concerns with viable crop production objectives. We conducted experiments to characterize dynamics and patterns of soil solution within wet bulb formed by drip irrigation. Time-domain reflectometry probes were used to monitor the distribution of potassium nitrate (KNO3) and water distribution from drippers discharging at constant flow rates of 2, 4 and 8 L h−1 in soil-filled containers. Considering results from different profiles, we observed greater solute storage near the dripper decreasing gradually towards the wetting front. About half of the applied KNO3 solution (48%) was stored in the first layer (0–0.10 m) for all experiments, 29% was stored in the next layer (0.10–0.20 m). Comparing different dripper flow rates, we observed higher solution storage for 4 L h−1, with 45, 53 and 47% of applied KNO3 solution accumulating in the first layer (0–0.10 m) for dripper flow rates of 2, 4 and 8 L h−1, respectively. The results suggest that based on the volume and frequency used in this experiment, it would be advantageous to apply small amounts of solution at more frequent intervals to reduce deep percolation losses of applied water and solutes.

The aim of this project was to conduct research into the effect of irrigation interval, using drip irrigation, on the depletion of available soil moisture and on corn yield, and the possible savings it might bring about in water, manpower, energy and other overheads. The experiments were carried out between 2000 and 2001 in the plain of Thessaly, central Greece. The experimental field had a complete randomized block design and consisted of three treatments (i.e. irrigation every 2, 5 and 9 days) for four replicates. Daily measurements were taken of the soil moisture content using the time domain reflectrometry (TDR) method and the depletion of available soil moisture was calculated. The amount of water used in each irrigation session was equal to the cumulative evapotranspiration between two successive irrigation sessions as measured using evaporation pan type A.Results showed that irrigation could be carried out every nine days instead of every two or even five days, thus bringing about substantial savings in the consumption of water. In addition, other overheads such as manpower, energy, etc. could be cut down with no statistically significant difference in crop yield. Copyright © 2008 John Wiley & Sons, Ltd.Le but de ce travail était de conduire une recherche sur l'effet de l'allongement de l'intervalle entre irrigations (maïs irrigué au goutte à goutte) sur la diminution de la réserve en eau du sol et sur le rendement, ainsi que les économies possibles sur l'eau, la main d'œuvre, l'énergie et les autres charges générales. Les expérimentations ont été conduites en 2000 et en 2001 dans la plaine de Thessalie en Grèce centrale. Le terrain expérimental comportait un bloc complet randomisé avec trois traitements (soit une irrigation tous les 2, 5 et 9 jours) et quatre répétitions. Des mesures ont été faites quotidiennement sur l'humidité du sol selon la méthode TDR (temps, domaine, réflectométrie) et la diminution de la réserve en eau du sol a été calculée. Le volume de chaque irrigation était égal à l'évapotranspiration cumulée entre deux irrigations successives telle que mesurée à l'aide d'un évaporomètre de type A.Les résultats ont montré que l'irrigation peut être réalisée tous les 9 jours au lieu de 5 ou de 2, conduisant ainsi à de substantielles économies d'eau. En outre d'autres charges telles que main d'œuvre, énergie, etc., ont pu être économisée sans différence significative de rendement. Copyright © 2008 John Wiley & Sons, Ltd.

A field experiment was conducted to study the effect of varying water application and soil pH on the growth parameters during the establishment of litchi (Litchi chinensis Sonn.) plantation in a partially reclaimed alkali environment. The plant growth parameters such as plant height and girth at collar were studied. Hydraulic performance of drip system was monitored by observing the individual and plant wise emitter discharge. The Christiansen's Coefficient of Uniformity (CCU), Wilcox-Swailes Coefficient of Uniformity (WSCU), Statistical Coefficient of Uniformity (SCU), Low Quarter Distribution Uniformity (SDUIq), and Coefficient for Emitter Flow Variation (CEFV) for the rate of water application were determined. The average value of CCU remained close to 0.63 and 0.75, respectively, on emitters' and plant basis when 4 drippers were employed per plant. Different levels of soil pH as experienced by the litchi plants were grouped into seven soil pH groups viz. less than 7.75, 7.75-8.00, 8.00-8.25, 8.25-8.50, 8.50-8.75, 8.75-9.00 and more than 9.00. In each of the above pH groups, different emitter discharges were observed. The plant wise discharges received in each pH group were further sub-divided and grouped in less than 10, 10-15, 15-20, 20-25, 25-30 and above 30 liter per hour (Ih?¹). The plant growth parameters were significantly different at different soil pH levels. The plant mortality was high and plant height and girth at collar reduced when the soil pH exceeded 8.5. A positive linear trend was observed in growth parameters and the application of discharge at or below a pH level of 8.5, after which the trend was reverse.

A field experiment was carried out during the two successive autumn seasons of 2013 and 2014
under open field conditions in protected cultivation site, Agriculture Research Centre, Giza
governorate, Egypt. The study was investigating the effects of different irrigation levels (50, 75 and 100% of crop evapotranspiration (ETc)) and different sources of fertilizers (inorganic fertilizers (control), cattle manure, compost and vermicompost) on some soil chemical characteristics and vegetative growth, yield and water use efficiency of head cabbage. Obtained results showed that soil pH decreased at the end of experiment with a range of 0.08-0.30, compared with before cultivation, with high decreases by 50% of ETc combined with vermicompost. ECe, on the other hand, increased due to different agricultural activities such as adding chemicals and fertilizers,

A study was conducted at the research farm of Central Soil Salinity Research Institute, Karnal, to evaluate the effect of salinity of irrigation water on the yield of okra (Abelmoschusesculentus L. Moench) under drip irrigation. The experiment was conducted in randomized block design with 4 levels of saline irrigation water (ECiw = 0.2, 2.0, 4.0, 8.0 dS.m-1) in three replications. Significant change in the yield of okra (Var: Mahyco-10 Hy) was observed at 1% level of significance. It was found that even at 8 dS.m-1 irrigation water salinity, 77% of okra yield to the check could be obtained. Highest water use efficiency was with available fresh water of 0.2 dS.m-1 at 0.49, and for the treatments of 2.0, 4.0, 8.0 dS.m-1 it was observed at 0.49, 0.46 and 0.38 t.ha-1.cm-1, respectively.