عنوان مقاله [English]
Salinity is the main problem of the fields under irrigation in many regions of the world which has been caused the farmers encountered with some questions such as determining of the optimum depth of irrigation water by using of saline water, reuse of drained water from the agricultural fields and yield reduction that resulting in reduction revenue by using of saline water. Water shortage and unsuitable quality of irrigation water are two main factors which has restricted the crop production in many regions of Iran. Among environmental stresses, salinity stress is the main factor of crop reduction. Many physiological processes of plants such as germination, seedling growth, flowering and fruit ripening are decrease by increasing in salt concentration in soil and irrigation water. Deficit irrigation and soil or irrigation water salinity decrease the matric and osmotic potential in soil water content respectively, which are resulting in reduction of water absorption by plant roots. Camelina (Camelina sativa L. Crantz) is a plant with oil seed from Brassicaceae family that interest to its planting has increased in recent years. The causes of that are high tolerance of this plant to unfavorable environmental conditions and usage possible of it for many purposes. Appropriate usage of yield- salinity- water crop production functions can be improved agricultural water consumption management in regions with scarce of water resources. Crop production functions such as linear form, Cobb-Douglas, quadratic and transcendental function models were used to simulate relative grain yield of camelina. As the area study in this research namely Kashmar plain, has been forbidden for withdraw of groundwater and many agricultural deep wells in this area have high salinity water, in order to optimum management water consumption in agriculture, determining of the best water-salinity-yield production function for crops such as oil seed plants (canola, seasame and camelina) are essential. For the first time, camelina was planted in Kashmar natural resource and agricultural research center as pilot plan in 2021. As the compounded effects of salinity and water stress on camelina grain yield has been not investigated in this area, the objective of this research was to obtain the optimum crop production function as affected by drought stress and irrigation with saline water.
A greenhouse experiment was conducted as a factorial in the form of a completely randomized design with three replications. The experiment treatments were four levels of salinity including drinking water S1=0.7, S2=4, S3=8 and S4= 12 dS m-1 and three levels of irrigation water including W1 (100% provided crop water requirement), W2=0.75W1 and W3=0.5W1 applied in a loamy sand soil texture with bulk density of 1.41 gr cm-3. Linear, Cobb-Douglas, quadratic and transcendental function models were used to simulate relative grain yield of camelina. In order to determine of optimum crop water production function, statistical analysis was done on obtained data and by determining of related statistics the role of each input was characterized quantitatively. For assessing of validation, the obtained functions, the statistics including maximum error (ME), root mean square error (RMSE), determining coefficient (R2), efficiency function (EF) and coefficient of residual mass (CRM) were used.
The results showed that quadratic function model was the most appropriate model for estimating of grain yield of camelina under pot planting conditions in greenhouse. Marginal product (MP) and marginal rate of technical substitution (MRTS) indices of grain yield related to quality and quantity of irrigation water showed that with increase a centimeter of irrigation water depth (hypothesized salinity is constant), camelina grain yield increased 56.8 kg ha-1. Also, MP related to irrigation water salinity indicated that with increase a unit of salinity (hypothesized irrigation water depth is constant) camelina grain yield decreased 38.7 kg ha-1. According to findings of this research it could be said that 70 mm depth of irrigation water and EC less than 4 dS m-1 is suitable for achievement to optimum grain yield of camelina under pot planting conditions in greenhouse. It is noteworthy that further consumption of water by plant (almost 300 mm) and longer of growth period duration of plant in field compared to pot planting conditions in greenhouse caused to production function coefficients recommended in this study would not be applicable in field conditions and it is necessary that supplemental studies would be conducted for determining of optimum yield- salinity- water production functions of camelina under field conditions.