Ali Ünlükara

Response of lettuce (Lactuca sativa var. crispa) to salinity of irrigation water

Abstract This study was conducted in a greenhouse to assess the response of lettuce (Lactuca sativa var. crispa) to increasing salinity of irrigation water (0.75, 1.5, 2.5, 3.5, 5.0, and 7.0 dS m−1). Soil salinity increased linearly with increasing salinity of irrigation water. The threshold value was determined as 1.1 dS m−1 and the relative yield decrease in slope after this threshold as 9.3%. The results showed that L. sativa var. crispa was moderately sensitive to salinity. In contrast to yield, plant dry matter content increased with increasing salinity for the salinity range studied. The taste of lettuce was not affected by salinity. The results further showed that the variables of leaf number per plant, plant height, water use efficiency, and accumulation of calcium (Ca) and iron (Fe) in the leaves decreased with salinity, whereas accumulation of potassium (K), nitrogen (N), copper (Cu), manganese (Mn), and zinc (Zn) in plant leaves was unaffected.

INTERACTIVE EFFECTS OF SALINITY AND N ON PEPPER (CAPSICUM ANNUUM L.) YIELD, WATER USE EFFICIENCY AND ROOT ZONE AND DRAINAGE SALINITY

The aim of this study was to determine the salt tolerance of pepper (Capsicum annuum L.) under greenhouse conditions and to examine the interactive effects of salinity and nitrogen (N) fertilizer levels on yield. The present study shows the effects of optimal and suboptimal N fertilizer levels (270 kg ha−1 and 135 kg ha−1) in combination with five different irrigation waters of varying electrical conductivity (EC) (ECiw = 0.25, 1.0, 1.5, 2.0, 4.0, and 6.0 dS m−1) and three replicates per treatment. At optimal N level, yield decreased when the irrigation water salinity was above ECiw 2 dS m−1. At the suboptimal N level, a significant decrease in yield occurred only above ECiw 4 dS m−1. At high salinity levels the salinity stress was dominant with respect to yield and response was similar for both N levels. Based on the results it can also be concluded that under saline conditions (higher than threshold salinity for a given crop) there is a lesser need for N fertilization relative to the optimal levels established in the absence of other significant stresses.

Alterations in antioxidant enzyme activities and proline content in pea leaves under long-term drought stress

The effects of long-term drought stress on chlorophyll, proline, protein and hydrogen peroxide (H2O2) contents, malondialdehyde (MDA) in terms of lipid peroxidation and on the changes in the activities of antioxidant enzymes such as superoxide dismutase (SOD, EC 1.15.1.1), ascorbate peroxidase (APX, EC 1.11.1.11), catalase (CAT, EC 1.11.1.6) and peroxidase (POX; EC 1.11.1.7) in the leaves of pea (Pisum sativum L.) were studied in field conditions. Chlorophyll and protein contents in leaves decreased significantly with increased drought stress. The proline content increased markedly under water deficit. MDA amounts were elevated as a result of water shortage, whereas H2O2 content changed slightly in pea leaves exposed to drought stress. Drought stress markedly enhanced the activities of SOD, CAT and POX but slightly changed the activity of APX. We conclude that in field conditions, long-term water shortage increased the susceptibility to drought in peas.

Salinity and drought affect yield response of bell pepper similarly

Abstract There is a growing realization that an increasing number of countries are approaching full utilization of their conventional water resources and that the quantity of good-quality water supplies available to agriculture is diminishing. Effects of irrigation regime and irrigation water salinity on bell pepper including yield, fruit number and quality, vegetative and root growth, evapotranspiration and water use efficiency were investigated in this study by conducting two different experiments. Six different salinity levels of irrigation water and four different irrigation regimes were used as treatments. Considering the results from irrigation water salinity experiment, it can be concluded that as soil salinity increases, water consumption, water use efficiency, yield and other vegetative growth parameters of bell pepper were decreased. A polynomial relationship between soil salinity and water consumption was observed. It was found that bell pepper is moderately sensitive to salinity with a 1.2 dS m−1 threshold and a 10.9% slope value. In the irrigation regime experiment, limited irrigation caused decreases in water consumption, yield and vegetative growth of bell pepper. Yield response factors were close in the cases of irrigation regime (1.50) and irrigation water salinity (1.40). Total soluble solids of bell pepper were increased due to both irrigation water salinity and water application rate but not dry matter ratio. Considerable water consumption decreases because of salinity were determined. Therefore, the effect of irrigation water salinity should be considered in irrigation management to prevent excess saline water application and to protect the environment.

Response of cowpea (Vigna unguiculata) to salinity and irrigation regimes.

Abstract The effects of salinity and irrigation regimes on yield, growth, and water consumption of cowpea (Vigna unguiculata) were determined in two different experiments. The first experiment focused on cowpea responses to irrigation water with six different levels of salinity (0.7, 2.0, 3.0, 4.0, 5.0, and 7.0 dS m−1). In the second experiment four different amounts of water (1.43, 1.0, 0.75, and 0.50 times of depleted water) were applied to cowpea plants. Seed and pod yields of cowpea decreased significantly for the soil salinity values higher than 9.0 dS m−1. As soil salinity increased, water consumption of cowpea decreased. Therefore, the effect of salinity in lowering evapotranspiration should be considered in irrigation planning and scheduling of cowpea. Either excessive or limited water applications caused decreases in seed and pod yields of cowpea. Yield response factor (Ky), from the relationships between relative evapotranspiration and relative yield decrease, were 0.98 and 0.92 for pod and seed yields, respectively. It is concluded that cowpea is tolerant to water stress in terms of seed and pod yields.

Nondestructive leaf-area estimation and validation for green pepper (Capsicum annuum L.) grown under different stress conditions

Leaf area of a plant is essential to understand the interaction between plant growth and environment. This useful variable can be determined by using direct (some expensive instruments) and indirect (prediction models) methods. Leaf area of a plant can be predicted by accurate and simple leaf area models without damaging the plant, thus, provide researchers with many advantages in horticultural experiments. Several leaf-area prediction models have been produced for some plant species in optimum conditions, but not for a plant grown under stress conditions. This study was conducted to develop leaf area estimation models by using linear measurements such as lamina length and width by multiple regression analysis for green pepper grown under different stress conditions. For this purpose, two experiments were conducted in a greenhouse. The first experiment focused to determine leaf area of green pepper grown under six different levels of irrigation water salinity (0.65, 2.0, 3.0, 4.0, 5.0, and 7.0 dS m−1) and the other under four different irrigation regime (amount of applied water was 1.43, 1.0, 0.75, and 0.50 times of required water). In addition to general models for each experiment, prediction models of green pepper for each treatment of irrigation water salinity and of irrigation regime experiments were obtained. Validations of the models for both experiments were realized by using the measurements belong to leaf samples allocated for validation purposes. As a result, the determined equations can simply and readily be used in prediction of leaf area of green pepper grown under salinity and water stress conditions. The use of such models enable researchers to measure leaf area on the same plants during the plant growth period and, at the same time, may reduce variability in experiments.

Growth, yield, and water use of okra (Abelmoschus esculentus) and eggplant (Solanum melongena) as influenced by rooting volume

Abstract Many experiments are conducted in simulated confined spaces to provide controlled environments where plants are grown in pots with limited rooting volume to characterise fundamental physiological responses of plants to stress conditions such as soil water, soil salinity, irrigation water salinity, and plant nutrition. However, rooting volume in the pots can have a limiting effect on overall plant growth to varying degrees. This study was undertaken to quantify the effects of widely differing rooting volume on growth, yield, and water use of eggplant (Solanum melongena) and okra (Abelmoschus esculentus). Eggplant and okra experiments were conducted similarly, but as separate experiments. Both plants were grown in 3.6‐litre (P1), 16‐litre (P2), 36‐litre (P3), and 52‐litre (P4) pots. For eggplant and okra, evapotranspiration (ET) and all of the growth parameters including plant height, stem diameter, root and vegetative dry weight, root length, number of branches and fruit, and fruit yield significantly increased with increasing rooting volume. Pot volume started to affect plant height and ET after 3 weeks from transplanting. For both experiments, the highest yield and the highest yield based water‐use efficiency (WUEyield) were obtained from the P4 and P3 treatments, respectively. The highest WUE based on total biomass (WUEbiomass) was obtained from the P4 and P3 treatment of eggplant and okra, respectively. Both experiments exhibited similar morphological changes such as decreases in plant height, stem diameter, branching, root and vegetative dry weight, and root length to root restriction. As a result of this study it can be concluded that a pot size of 36 litres (P3) may be enough for okra growth, but even a 52‐litre (P4) pot size may not provide unrestricted rooting volume for eggplant growth.

CHANGE IN YIELD AND CHEMICAL COMPOSITION OF TALL FESCUE (Festuca arundinacea Schreb.) PLANTS UNDER SALT STRESS

The present study was conducted to investigate the effects of different irrigation water salinity levels (0, 3, 5 and 8 dS/m) on hay yield, chemical composition, gas and methane production, metabolic energy (ME) and organic matter digestibility (OMD) of plants. Experiments were conducted in randomized blocks design with four replications for two years (2014-2015). Calcium chloride (CaCl2), sodium chloride (NaCl) and magnesium sulfate (MgSO4) salts were used to prepare irrigation waters with different salinity levels. Drip irrigation was used. Fresh and dry hay yields, plant height, acid detergent fiber, neutral detergent fiber and crude oil contents decreased with increasing salt doses. Tall fescue Olympus cultivar exhibited a moderate tolerance to salinity. Fresh hay yield decreased by 8.2% at 1.85 dS/m threshold salinity level and dry hay yield decreased 8.2% at 1.97 dS/m threshold salinity level. Crude protein content, gas and methane production, net energy lactation, metabolic energy and organic matter digestibility increased with increasing salt doses. Despite the decreases in hay yield, 8 dS/m did not result in any decreases in protein yields and resulted in low gas and methane production.

Farklı Yıkama Oranlarında Sulama Uygulamalarının Fasulyenin (Phaseolus vulgaris) Gelişimine ve Besin Maddesi İçeriğine Etkisi

In this study, effects of different leaching fractions on soil salinity and its mineral composition were investigated. Additionally, fresh bean yield and mineral matter accumulation in its leaf shoot and fruit were determined. The experiment conducted in randomized plot design with 4 leaching treatments (LF1= 0.00, LF2= 0.15, LF3= 0.30 and LF4= 0.50) and leaching exhibited with each irrigation throughout the experiment. Saline irrigation water at 2.5 dS m-1 level prepared with CaCl2 and NaCl salts were used to irrigate bean plants. Fresh bean yield increased as leaching fraction increased to 0.30 leaching ratio while soil salinity decreased with increasing leaching fraction. Fresh bean yields for LF1, LF2, LF3 and LF4 were 78.0, 114.9, 141.6 and 127.0 g pot-1, respectively. Soil salinity increased 3.4, 2.0, 1.7 and 1.2 times with respect to irrigation water salinity level for LF1, LF2, LF3 and LF4, respectively. Mg/Ca ratio in saturation paste extract decreased with increasing leaching ratios. Increased leaching ratios caused increases in P content of shoot and fruit and decreases in Ca and Mg content of shoot and decreases in both shoot and fruit of N content.