تأثیر رطوبت خاک و کمپوست لجن فاضلاب بر شاخص کلروفیل برگ و برخی ویژگی‌های رشد گیاه یونجه در شرایط گلخانه‌ای

Due to low organic matter content in most of the cultivated soils of Iran and occurrence of drought stress in plants because of low precipitation, application of sewage sludge compost has been recommended for increasing soil organic matter content and improving soil fertility, increasing crop tolerance to water deficit and improving crop yield. So, in this study, the effects of soil moisture and sewage sludge compost levels were investigated on leaf chlorophyll index and some growth traits of alfalfa (Medicago sativa L.) in greenhouse conditions. A factorial experiment, based on randomized complete blocks design with three replications, was conducted with two factors of soil moisture conditions at three levels (0.81FC-FC, 0.56FC-0.75FC and 0.35FC-0.50FC) and sewage sludge compost at four levels (0, 15, 30 and 60 g/kg of soil). Results showed that the effect of soil moisture levels on leaf chlorophyll index was dependent on the level of sewage sludge compost. Soil water deficit significantly decreased shoot and root dry weights and plant height (P<0.01). The sensitivity of alfalfa shoot to soil water deficit stress was greater than its root. Application of 15 and 30 g sewage sludge compost per kg of soil significantly increased leaf chlorophyll index, shoot and root dry weights, plant height and shoot to root dry weight ratio (P<0.01). The interaction effects of soil moisture and sewage sludge compost on leaf chlorophyll index, shoot and root dry weights, plant height and shoot to root dry weight ratio were significant (P<0.01). The highest shoot and root dry weights, plant height and shoot to root dry weight ratio were observed at 30 g sewage sludge compost per kg of soil and 0.81FC-FC soil moisture level. Also, the results showed that application of 30 g sewage sludge compost per kg of soil alleviated water deficit-induced adverse effects on alfalfa plant.