Attila Yazar

Evaluation of crop water stress index for LEPA irrigated corn

Abstract This study was designed to evaluate the crop water stress index (CWSI) for low-energy precision application (LEPA) irrigated corn (Zea mays L.) grown on slowly-permeable Pullman clay loam soil (fine, mixed, Torrertic Paleustoll) during the 1992 growing season at Bushland, Tex. The effects of six different irrigation levels (100%, 80%, 60%, 40%, 20%, and 0% replenishment of soil water depleted from the 1.5-m soil profile depth) on corn yields and the resulting CWSI were investigated. Irrigations were applied in 25 mm increments to maintain the soil water in the 100% treatment within 60–80% of the “plant extractable soil water” using LEPA technology, which wets alternate furrows only. The 1992 growing season was slightly wetter than normal. Thus, irrigation water use was less than normal, but the corn dry matter and grain yield were still significantly increased by irrigation. The yield, water use, and water use efficiency of fully irrigated corn were 1.246 kg/m2, 786 mm, and 1.34 kg/m3, respectively. CWSI was calculated from measurements of infrared canopy temperatures, ambient air temperatures, and vapor pressure deficit values for the six irrigation levels. A “non-water-stressed baseline” equation for corn was developed using the diurnal infrared canopy temperature measurements as Tc–Ta = 1.06–2.56 VPD, where Tc was the canopy temperature (°C), Ta was the air temperature (°C) and VPD was the vapor pressure deficit (kPa). Trends in CWSI values were consistent with the soil water contents induced by the deficit irrigations. Both the dry matter and grain yields decreased with increased soil water deficit. Minimal yield reductions were observed at a threshold CWSI value of 0.33 or less for corn. The CWSI was useful for evaluating crop water stress in corn and should be a valuable tool to assist irrigation decision making together with soil water measurements and/or evapotranspiration models.

Yield and Water Use Efficiency of Corn in Response to LEPA Irrigation

Center-pivot sprinklers are rapidly expanding on the Southern High Plains, and LEPA (low energy precision application) application methods are widely used in this region to reduce water application losses, to use the relatively low well yields, and to reduce energy requirements for pressurization. This study was conducted to evaluate LEPA irrigation response of corn (Zea mays L.) on slowly permeable Pullman clay loam (fine, mixed, thermic Torrertic Paleustoll). The effects of irrigation amount were investigated in a field study during the 1992 and 1993 cropping seasons at Bushland, Texas. In 1992, a wetter than normal season, grain yields varied from 0.6 to 1.2 kg/m2 while in 1993, which was a season with slightly less than normal rain, grain yields varied from 0.4 to over 1.5 kg/m2 as irrigations increased from no-post plant irrigations to fully meeting the crop water use. Irrigation amounts for the full irrigation varied from only 279 mm for the wet year to over 640 mm for the more normal year. A significant relationship was found between grain yield and water use for the two years described as GY (kg/m2) = 0.00169 [WU (mm) – 147] with an r2 of 0.882 and a Sy/x of 0.10 kg/m2. Deficit irrigation of corn, even with LEPA, reduced yields by affecting both seed mass and kernels per ear. Generally, the grain yield was in proportion to dry matter yield. LEPA irrigation was shown to be efficient in terms of partitioning the applied water into crop water use. Irrigation amounts should not exceed 25 mm for alternate furrows (0.76-m rows) LEPA on the Pullman-type soils with furrow dike basins.

Evaporation and drift losses from sprinkler irrigation systems under various operating conditions

Abstract Quantitative determinations of evaporation and drift losses from sprinkler systems were carried out under different operating conditions. Evaporation losses determined by an electrical-conductivity method ranged from 1.5 to 16.8% of the total sprinkled volume. Wind velocity and vapor pressure deficit were the most significant factors affecting the evaporation losses. Exponential relationships between the evaporation losses and both wind velocity and vapor pressure deficit have been found. For the operating pressures used in this study the least effect on evaporation was found. Drift losses measured by the magnesium-oxide method varied from 1.5 to 15.1%. Drift losses increased with the second power of the wind velocity, and decreased with increasing distance in the downwind direction. Combined losses from a sprinkler system for a given set of operating conditions have been estimated by using the results obtained from the experiments. Combined losses ranged from 1.7 to 30.7% of the applied water.

Irrigation response of Pistachio (Pistacia vera L.)

Pistachio yields normally alternate between high and low values for consecutive years due to management and genetic effects. In this study, irrigated and non-irrigated treatments of old pistachio trees (Pistacia vera L.) were compared for 5 years from 1979 to 1983. Two irrigation treatments consisting of irrigation scheduling at 20- and 30-day interval were compared with the control treatment of no irrigation. Results showed that irrigation practice in pistachio orchards not only increased fruit yield, but also suppressed periodicity, the low fruit yield in alternating years. The frequent irrigation of 20-day interval nearly doubled the dry fruit yield irrespective of whether it was the off-yielding year, compared to non-irrigated control treatment. Three-years average for the irrigation at 20 days interval was 5710 kg per ha during the on-yielding years (1979,1981 and 1983); whereas, the control treatment of no irrigation yielded only 3450 kg per ha during the same period. Two-year average of the non-irrigated treatment, during the off-yielding years (1980 and 1982) was 1730 kg per ha; whereas, the irrigated treatment of 20-day interval, for the same period, showed significantly (P ≤ 0.05) higher fruit yield (4030 kg per ha). Irrigation treatments, during both on and off-yielding years, had no effect on fruit quality characteristics such as nut weight, blank and split shell percent, etc. The root activity under frequent irrigation treatment was confined to shallower soil depth than the longer interval irrigation treatment.

Evapotranspiration of grapefruit in the eastern Mediterranean region of Turkey

Abstract Different pan coefficients (k1 = 0.6 and k2 = 1.0) and irrigation intervals (I1 = 15 and I2 = 25 days) were used in this study. The average total evapotranspiration (Et) was 1039 mm (for I1k2) and 988 mm (for I2k2). Effective root depth of grapefruit varied from 90 to 110 cm depending on the irrigation intervals. Calculated pan coefficients ( Et Eo ) reached a maximum value of 1.2 in treatment I1k2 in spring and winter owing to the contribution of higher rainfall. However, calculated coefficients in the irrigation season were lower than the ones applied in this study. There were no significantly different effects of irrigation treatments on the yields of grapefruit, but the yield from irrigation interval of 15 days was slightly higher. In periodicity years, yields and the number of fruits decreased by 52-45% and 85-77% with respect to the irrigation treatments. In years of normal yield, the average fruit weight was about 32% lower and seed number was two to four times higher than in periodicity years. In years of normal yield, water use efficiency (WUE) was highest in treatment I1k1. Overall and irrigation WUE values decreased by 51% and 46% in periodicity years, respectively.

Water Harvesting in Dry Environments

As water shortage in the dry areas is a recurrent crisis, people have a great need for information on how to capture and use every available drop of water efficiently. Water harvesting is an effective and economical means of achieving this objective and information on its various systems and techniques is in great demand. Water harvesting has been practiced successfully for millennia in parts of the world – and some recent interventions have also had significant local impact. Yet water harvesting’s potential remains largely unknown, unacknowledged and unappreciated. Water harvesting offers under-exploited opportunities for the predominantly rainfed farming systems of the drylands in the developing world. It works best in precisely those areas where rural poverty is worst. When practiced well, its impact is to simultaneously reduce hunger and alleviate poverty, as well as to improve the resilience of the environment. Rainfall is the most important natural resource in drier environments. Low rainfall, water scarcity and land degradation severely inhibit the production capacities of agricultural lands in arid and semiarid environments. Improving the efficiency of rainwater use is, therefore, extremely critical in these water-scarce areas with rapidly expanding, poor populations living in a fragile environment and facing food insecurity and depleted natural resources bases. Water harvesting is increasingly important for improving the management of water resources in such dry environments. This chapter deals with the methods and techniques of water harvesting to make more water available to humans, animals and for irrigation purposes, in places where rainwater is the only source of water. Details are provided on the main factors for selection of reliable water harvesting technique that is sustainable under local circumstances, including physical (hydrologic, terrain, and technical), cultural acceptability and socioeconomic (institutional and economic) factors. The aim is to compile a synthesis of experiences that can provide insight into rainwater harvesting opportunities which address human wellbeing while continuing to sustain a range of ecosystem services.

Saline water irrigation of quinoa (Chenopodium quinoa) under Mediterranean conditions

Abstract. Field experiments were set up in order to evaluate the yield response of quinoa (Chenopodium quinoa Willd. cv. Titicaca) to irrigation with saline and fresh water under Mediterranean climate from 2010 to 2012 in Adana, Turkey. Irrigation treatments in 2010 and 2011 comprised full irrigation with fresh water, full irrigation with saline water of different salt concentrations (40, 30, 20, 10 dS m–1), deficit irrigations with fresh water (50%, 75% of full irrigation), partial root-zone drying, and deficit irrigation with saline water of 40 dS m–1 (50%). In 2012, in addition to the full irrigation treatments, two deficit irrigation levels of 67% and 33% of full irrigation with fresh or saline (30, 20, 10 dS m–1) water were considered. The results indicated that grain yields were slightly reduced by irrigation water salinity up to 30 dS m–1 compared with fresh water irrigation. Salinity and drought stress together interfered considerably with crop grain and biomass yields. However, salinity stress alone did not interfere with grain and biomass yield significantly; therefore, quinoa may be defined as a crop tolerant to salinity. Yield parameters such as aboveground biomass, seed yield and harvest index suggested a good adaptation of quinoa cv. Titicaca to Mediterranean environments.

Trends in performance of Turkish durum wheats derived from the international maize and wheat improvement center in an irrigated West Asian and North African environment

Turkey is one of the most important durum wheat ( T. turgidum L. var. durum Desf.) producers in West Asia and North Africa (WANA). There appears to have been a lack of progress in wheat yields in WANA over recent decades. Most of the modern cultivars grown in WANA are related to crosses produced by the International Maize and Wheat Improvement Center (CIMMYT). During 1999 and 2000, a chronological set of 11 cultivars related to CIMMYT crosses was evaluated using two irrigation regimes near Şanliurfa, Turkey. Average yields ranged from 386 g/m 2 (local cultivar, Karakilcik-33) to 614 g/m 2 (Ege-88). When wheat cultivars were grown with irrigation until physiological maturity, cessation of irrigation near anthesis reduced average grain yields of all cultivars by 6·2–25·7%. Since the introduction of the first generation of CIMMYT cultivars in 1975, CIMMYT grain yields have increased by about 0·60% per year compared with that of Karakilcik-33. This rate increased up to 1·08% per year until 1988. No further progress in yield was measured for varieties released in the 1990s. The average rate was 0·76% per year. After the introduction of the CIMMYT cultivars, yield changes fitted better in a quadratic function. Compared with Karakilcik-33, the yield increases of CIMMYT cultivars have resulted from an increase in harvest index associated with reduced height and the development of more and heavier grains. Grain quality traits decreased with the introduction of the first CIMMYT cultivar but recovered slightly thereafter with no clear trend. The results are discussed with consideration of breeding priorities and specific WANA conditions.