Search Results (5)

Aerated irrigation (AI) has emerged as a method to mitigate rhizosphere hypoxia caused by wetting front with sub-surface drip irrigation (SDI). Increasing oxygen in processing tomato’s root zone is beneficial to the improvement of the rhizosphere gas environment, crop growth, yield and quality. The relationship between aerated irrigation and irrigation quantity is not clear. A total of eight treatments, including four irrigation levels (4950 m³ hm⁻² (W1), 4750 m³ hm⁻² (W2), 4500 m³ hm⁻² (W3), 4050 m³ hm⁻² (W4)) in combination with aerated irrigation (A2) and non-aerated irrigation (A1) were used to investigate the effects of aerated irrigation on the physiological characteristics and yield of processing tomatoes under mulched drip irrigation in Xinjiang, China. The effects of aerated irrigation on plant height, stem diameter, leaf area index and dry matter, photosynthesis, fluorescence, fruit quality and yield of processing tomatoes were studied. The results showed that plant height, stem diameter, biomass accumulation and leaf area index of processing tomatoes under aerated irrigation were increased by 10.2%, 7.3%, 12.5% and 6.2% under the W1, W2, W3 and W4 conditions (p < 0.05), respectively, compared with non-aerated irrigation. Yield and the content of Vitamin C and soluble solids under aerated irrigation was 9.71%, 5.59% and 5.68% (p < 0.05) higher than that under conventional irrigation, respectively, and the sugar-acid under aerated irrigation decreased by 0.5%. Through principal component analysis, W2A2 treatment had a higher score according to the yield index (per fruit weight, fruit number per plant) and quality index (Vitamin C, soluble solids, sugar-acid ratio) than the other treatments. The results show that aerated irrigation is feasible under the existing mulched drip irrigation in Xinjiang and, in this experiment, W2A2 treatment was the most suitable planting mode. Full article

Knowledge of carbon (C) and nitrogen (N) dynamics under different irrigation practices in pomegranate orchards is novel and essential to develop sustainable production systems. The aim of this research was to determine the effect of high-frequency drip irrigation and different rates of N fertilizer on C and N distribution in the soil and N uptake by pomegranate fruit and leaves. The main treatments were surface drip irrigation (DI) and subsurface drip irrigation (SDI), and the sub-treatments used were three initial N rates (N1, N2, and N3). As trees grew larger, the N application rate increased. From 2013–2015, trees received the following rates of N: 62–113 (N1), 166–263 (N2), or 244–342 kg/ha (N3). Soil and leaf total C (TC) and N (TN), soil dissolved organic C (DOC), soil nitrate (NO₃⁻), and total N uptake by fruit were evaluated between 2012 and 2015. Soil samples were collected to 120 cm depth at 15 cm increments. DI resulted in higher concentrations of TN, TC, NO₃⁻, and DOC in the upper 75 cm depth than SDI. The N3 treatment resulted in higher concentrations of TN, TC, NO₃⁻, and DOC under both DI and SDI. Neither DI nor SDI at the N1 or N2 levels increased TN and NO₃⁻ concentrations at 105–120 cm soil depth, indicating reduced leaching risk using high-frequency drip irrigation. Higher N uptake by fruit was observed in SDI than in DI in 2014 and 2015, and in N2 and N3 treatments compared with N1 in 2013 and 2014. The data indicate that the application rate at 166–263 kg/ha (N2) provided sufficient N for a 4–6-year-old pomegranate orchard and that high-frequency SDI is a promising technology for achieving higher N use efficiency and minimizing leaching loss of NO₃⁻ and DOC. Full article

The availability of brackish groundwater in the Negev Desert, Israel has motivated the cultivation of various salinity tolerant crops, such as olives trees. The long term suitability of surface drip irrigation (DI) or subsurface drip irrigation (SDI) in arid regions is questionable, due to salinity concerns, in particular, when brackish irrigation water is employed. Nevertheless, DI and SDI have been adopted as the main irrigation methods in olive orchards, located in the Negev Desert. Reports on continued reduction in olive yields and, essentially, olive orchard uprooting are the motivation for this study. Specifically, the main objective is to quantify the spatial distribution of salinity and sodicity in the active root-zone of olive orchards, irrigated with brackish water (electrical conductivity; EC = 4.4 dS m⁻¹) for two decades using DI and subsequently SDI. Sum 246 soil samples, representing 2 m² area and depths of 60 cm, in line and perpendicular to the drip line, were analyzed for salinity and sodicity quantities. A relatively small leaching-zone was observed below the emitters depth (20 cm), with EC values similar to the irrigation water. However, high to extreme EC values were observed between nearby emitters, above and below the dripline. Specifically, in line with the dripline, EC values ranged from 10 to 40 dS m⁻¹ and perpendicular to it, from 40 to 120 dS m⁻¹. The spatial distribution of sodicity quantities, namely, the sodium adsorption ratio (SAR, (meq L⁻¹)^0.5) and exchangeable sodium percentage (ESP) resembled the one obtained for the EC. In line with the dripline, from 15 to 30 (meq L⁻¹)^0.5 and up to 27%, in perpendicular to the drip line from 30 to 60 (meq L^−l)^0.5 and up to 33%. This study demonstrates the importance of long terms sustainable irrigation regime in arid regions in particular under DI or SDI. Reclamation of these soils with gypsum, for example, is essential. Any alternative practices, such as replacing olive trees and the further introduction of even high salinity tolerant plants (e.g., jojoba) in this region will intensify the salt buildup without leaving any option for soil reclamation in the future. Full article

To reveal the impact of soil moisture distributions on nitrous oxide (N₂O) emissions from wet soils irrigated by sub-surface drip irrigation (SDI) with different surface soil wetting proportions, pot experiments were conducted, with surface irrigation (SI) as a control. Results indicated that irrigation triggered N₂O pulsing effect in all SDI treatments, yet N₂O values reduced with the decrease of surface soil wetting proportions of SDI irrigated soils, and the occurrence times were lagged. The peak N₂O fluxes and the corresponding soil water filled pore space (WFPS), as well as the coefficients of determination (R²) of the exponential function between N₂O fluxes and soil WFPS, decreased with the reduction of surface soil wetting proportions with SDI treatment, and from the central sub-region to the periphery sub-region. The pulse period contributed most to the reduction of N₂O emissions in SDI compared to SI treatments and should be a key period for N₂O emission mitigation. Over the whole experimental period, the area-weighted average cumulative N₂O fluxes from SDI treatments were 82.3–157.3 mg N₂O m⁻² lower than those from SI treatment, with periphery sub-regions of R3 and R4 (radius of 19–27 cm and 28–36 cm from the emitter horizontally) contributing to more than 75.8% of the total N₂O emission mitigation. These results suggest that reducing surface soil wetting proportions or the increments of topsoil WFPS for SDI irrigated soils is a promising strategy for N₂O emission reduction. Full article

In California, alfalfa is grown on a large area ranging between 325,000 and 410,000 hectares and ranks among the thirstiest crops. While the hay production industry is often scrutinized for the large usage of the state’s agricultural water, alfalfa is a crucial feed-supplier for the livestock and dairy sectors, which rank among the most profitable commodity groups in the state. Sub-surface drip irrigation (SDI), although only practiced on approximately 2% of the alfalfa production area in California, is claimed to have the potential to significantly increase hay yield (HY) and water productivity (WP) compared with surface irrigation (SI). In 2014–2016 we interviewed a number of growers pioneering SDI for alfalfa production in Central and Southern California who reported that yield improvements in the order of 10–30% and water saving of about 20–30% are achievable in SDI-irrigated fields compared with SI, according to their records and perceptions collected over few years of experience. Results from our research on SDI at the University of California, Davis, revealed significantly smaller yield gain (~5%) and a slight increase of water use (~2–3%) that are similar to findings from earlier research studies. We found that most of the interviewed alfalfa producers are generally satisfied with their SDI systems, yet face some challenges that call for additional research and educational efforts. Key limitations of SDI include high investment costs, use of energy to pressurize water, the need for more advanced irrigation management skills, and better understanding of soil-water dynamics by farm personnel. SDI-irrigated fields also need accurate water monitoring and control, attentive prevention and repair of rodent damages, and careful salinity management in the root zone. In this paper we attempt to evaluate the viability of the SDI technology for alfalfa production on the basis of preliminary results of our research and extension activities, with focus on its water and energy footprints within the context of resource efficiency. Full article