End Of Irrigation Season Research Articles

The effect of flushing frequency on emitter's emission uniformity coefficient when using of Sanandaj city, Iran

Abstract. The increasing population growth, heterogeneous distribution of water resources and periodical drought in the search for finding new sources of water is inevitable. Today, the use of treated wastewater is an important management option in the planning of water resources in many countries. Drip irrigation system is the best method for using treated wastewater. Emitters clogging are the most important drawback of the systems using treated wastewater. Clogging results in reducing the efficiency and distribution uniformity coefficient in drip irrigation. Therefore, a physical model of drip irrigation was designed and made for studying the effect of flushing frequency on the clogging reduction of Micro Flapper emitter and irrigation tapes. The mean discharge, discharge variations coefficient, and Christiansen's coefficient of distribution uniformity were used as indices for evaluating the clogging of the emitters. The results indicated that when using treated wastewater, the clogging of the emitters increased with time but their distribution uniformity reduced. Moreover, the research indicated that flushing at the end of irrigation season significantly causes increasing emitters’ discharge. In addition, it was found that monthly flushing results in the higher distribution uniformity coefficient and less discharge variations coefficient in Micro Flapper emitter and irrigation tape. The effect of flushing frequency and emitter type on the percentage of discharge reduction and discharge variations coefficient of the emitters was significant at one percent statistical level.

The Temporal Variation of Leaf Water Potential in Pistachio under Irrigated and Non-Irrigated Conditions

The present study was carried out in the experimental field of Pistachio Research Institute on pistachio trees which has uzun variety that was 30 years old. The aim of this research was to determine the Leaf Water Potential (LWP) of Pistacia vera L. under irrigated and non-irrigated conditions. In the study, the leaf water potential of pistachio was investigated under fully irrigated and non irrigated conditions. The leaf water potential values were measured one day before and after irrigation by using pressure chamber technique at the beginning, mid and end of irrigation season. According to the results obtained from measurements, the LWP value at the beginning of the irrigation season was -3.7 MPa at noon time due to relatively high temperature for both treatments. At the time of pre-dawn and sunset, this value increased and reached to -1.6 MPa due to relatively low temperature. In general, the LWP values during the mid of irrigation season, in the irrigated treatments, reached to almost -2.5 MPa in the non-irrigated treatment and the value was measured as -3.68 MPa.

Transient soil salinity under the combined effect of reclaimed water and regulated deficit drip irrigation of Mandarin trees

Regulated deficit irrigation (RDI) strategy using saline reclaimed water is becoming a frequent practice under semiarid Mediterranean climatic conditions in the southeastern region of Spain. There is a concern that the long-term use of this strategy will affect the production sustainability of the agricultural soils. This paper evaluates the field consequences of this strategy on the accumulation of salts within the plant root zone. Full and regulated deficit surface drip deficit irrigation was combined with fresh water (EC 1dSm−1) and saline (EC 3dSm−1) tertiary reclaimed water to irrigate adult mandarin trees over a 3-year period. The control treatment received 100% of the crop evapotranspiration “ETc” and the RDI treatment received 50% of ETc during the 2nd stage of fruit growth. Soil water content was monitored every other week within the soil wetted volume under the emitter. Gravimetric soil samples were collected from 3 depths and at 3 distances to the emitter, twice a year: at the end of irrigation season and at the conclusion of RDI period. Soluble salts, electrical conductivity and sodium adsorption ratio were determined in the saturated paste extract. The results show how the RDI strategy intensifies the development of salinity gradient away from the emitter even when using good quality water. The combination of RDI with saline reclaimed water produced transient saline-sodic conditions at the outer superficial limits of the wetted bulb under the emitter. The appearance of such adverse conditions is alarming and would threaten the sustainability of agricultural soils. Therefore soil water deficit should be avoided whenever saline reclaimed water is in use for irrigation.

Effect of Waste Water Irrigation and Leaching Percentage on Soil and Ground Water Chemistry

AbstractIrrigation with sewage waste water for six seasons produced greater salinity under alfalfa (Medicago sativa L.) than under reed canary grass (Phalaris arundinacea L.) or fallow. Irrigation rates were designed to produce high and low leaching percentages (LP). The high irrigation rate (I2) was double the low irrigation rate (I1). Leaching percentages were estimated from the soluble Na concentration at the 90‐ to 150‐cm depth of the soil profile. At the 90‐ to 150‐cm depth of the soil profile, Na reached a steady state for the conditions of the irrigation season by the fall of each year in the first 2 crop years and by the end of the second irrigation season in the last 4 crop years. At the water table depth (2–4 m), Cl in the ground water was close to an annual steady‐state concentration by the end of each irrigation season in the first 2 crop years and by the end of the second irrigation season in the last 4 crop years. Sodium and Ca + Mg approached equilibrium during the final 3 crop years.High LPs (>34%) in the first 2 years reduced original salinity levels [electrical conductivity (EC) 3.99 to <1.39 mmhos/cm]. When irrigation rates were reduced in the last 4 years, salinity increased, but the salt levels were well below those (EC <2.13 mmhos/cm) that would significantly reduce crop yield.Ground water calculations at low LP (<10%) showed that EC and sodium adsorption ratio (SAR) values were high, but CaCO3 precipitation was balanced by gypsum dissolution. By comparison, at high LPs (>15%) the EC and SAR values were low, but there was a potential danger of a large net transfer of salt to ground water because of gypsum dissolution.