No abstract

An experiment was conducted to investigate the influence of different levels of water deficit on yield and crop water requirement of soya beans in a sub‐humid environment (Southern Marmara region, Bursa, Turkey) in 2005 and 2006. One full‐irrigated treatment (T1), one non‐irrigated treatment (T5) and three different deficit irrigation (T2 = 25 % water deficit, T3 = 50 % water deficit, T4 = 75 % water deficit) treatments were applied to ‘Nova’ soya bean planted on a clay soil. Non‐irrigated and all deficit irrigation treatments significantly reduced biomass and seed yield and yield components. The full‐irrigated (T1) treatment had the highest yield (3760 kg ha−1), while the non‐irrigated (T5) treatment had the lowest yield (2069 kg ha−1), a 45.0 % seed yield reduction. T2, T3 and T4 deficit irrigation treatments produced 11.7–27.4 % less seed yield than the T1 treatment. Harvest index showed less and irregular variation among irrigation treatments. Both leaf area per plant and leaf area index were significantly reduced at all growth stages as amount of irrigation water was decreased. Evapotranspiration increased with increased amounts of irrigation water supplied. Our results indicate that higher amounts of irrigation resulted in higher seed yield, whereas water use efficiency and irrigation water use efficiency values decreased when irrigation amount increased.

This study examined the effects of different irrigation levels and nitrogen rates on perennial ryegrass (Lolium perenne L.) evapotranspiration and quality in a sub-humid climate over a two-year period (2007)(2008). Nitrogen treatment (25 kg N ha -1 ; N 1 and 50 kg N ha -1 ; N 2 ) varied among main plots and irrigation levels (25%; I 1 , 50%; I 2 , 75%; I 3 , 100%; I 4 and 125%; I 5 of the Class A pan evaporation) by subplot. Irrigation was performed at 3-day intervals during May-September using a pop-up sprinkler irrigation system, and N applied as a monthly rate during the irrigation period. Seasonal turfgrass evapotranspiration was found to vary by treatment from 309-1178 mm in 2007 and from 379-1097 mm in 2008. Turfgrass visual color, quality and clipping yield were shown to decrease significantly with decreases in irrigation water and N fertilizer. The study findings demonstrated that under a non-limiting water supply, irrigation could be decreased by adjusting N fertilizer rates according to turfgrass visual color and quality and that N 1 I 4 or N 2 I 3 treatments can maintain acceptable turfgrass visual color and quality under sub-humid climatic conditions.

A 2-year experiment was conducted to investigate the effects of different irrigation levels and nitrogen rates on visual turfgrass colour and quality and clipping yield of tall fescue (Festuca arundinacea Schreb.) under subhumid climatic conditions. The treatments consisted of five levels of irrigation, 25% (I1), 50% (I2), 75% (I3), 100% (I4) and 125% (I5), of the evaporation measured from a Class A pan and two rates of nitrogen, 25 kg N ha -1 (N1) and 50 kg N ha -1 (N2). The N rates were applied as a monthly rate during growing seasons (MaySeptember). The experimental area was irrigated by a pop-up sprinkler irrigation system. The irrigation was applied at 3-day intervals during May-September for both years. The seasonal crop evapotranspiration (ETc) under the treatments ranged from 315 to 1154 mm in 2007 and from 363 to 1100 mm in 2008. The ETc increased with increasing the both N rate and irrigation level, and the best seasonal turf quality of tall fescue was obtained for the I4 and I5 treatments under N2 rate. This study demonstrated that, when the level of irrigation and nitrogen rate were evaluated together, the N2I4 treatment ensured sufficiently dark turf colour and quality. Based on the results of this study, it is concluded that an acceptable turf quality can be sustained under the N1I1 treatment in May, N1I2 treatment in June, July and August and N1I4 treatment in September (or N2I2 treatment in September) according to water conservation. When rainfall amountis high (132.2 mm) in September, the N1I1 treatment may sustain acceptable turf quality for this month.

Field experiments were conducted in 2019 and 2021 growing seasons to evaluate the chlorophyll readings and crop water stress index (CWSI) response to full and deficit irrigation for drip-irrigated sugar beet ( Beta vulgaris L.) under sub-humid climate of Bursa, Turkey. In addition, the changes of soil water content under different irrigation treatments and statistical relationships between chlorophyll and CWSI values and ET c , root yield and sugar yield were investigated. Experiments were carried out in a completely randomized blocks design with three replications. Irrigations were scheduled based on the replenishment of 100 (S1), 66 (S2), 33 (S3), and 0% (S4) of soil water depletion within the soil profile of 0–90 cm using 7 day irrigation intervals. Lower and upper baselines obtained by measurements based on the canopy temperature from the treatments full irrigated and non-irrigated were used to calculate CWSI. The variations in CWSI values were consistent with the variations of seasonal soil water contents induced by the different irrigation practices. CWSI values generally varied between 0 and 1 throughout the experimental periods. In 2019, seasonal mean chlorophyll readings varied between 203.3 and 249.1, and mean CWSI values varied between 0.12 and 0.85. In 2021, seasonal mean chlorophyll readings varied between 232.7 and 259.3 and mean CWSI values between 0.19 and 0.89. Unlike chlorophyll values, CWSI decreased with increased irrigation water amount. In both years, statistically significant relationships were determined between chlorophyll readings and CWSI and ET c , root yield and sugar yield. The greatest root yield was achieved with a seasonal mean CWSI value of 0.12. An exponential equation determined as “Root Yield = 10.804e −1,55CWSI ” between seasonal average CWSI values and root yield can be used for estimation of root yield in sugar beet farming. The mean CWSI values determined by infrared thermometer technique can be used in determination of crop water stress and irrigation scheduling of sugar beet cultivation under sub-humid climatic conditions.