Irrigation, Phosphorus Fertilizer and Phosphorus Solubilizing Microorganism Effects on Yield and Forage Quality of Turnip (Brassica rapa L.) in an Arid Region of Iran

Turnip has a high potential to produce abundant nutritious and valuable forage when availability of perennial warm and cool-season species is limited. Water deficit and fertility affect not only growth and yield of crops but also their quality and nutritional value. To evaluate the effect of different phosphorous fertilizers on forage yield and quality of turnip under deficit irrigation regimes, a field experiment was conducted during 2009. The experimental treatments arranged as split plots were five levels of irrigation, no irrigation (IR0), irrigation at sowing time (IR1), irrigation at sowing time ? commencement of tuber formation (IR2), (irrigation at sowing time ? commencement of tuber formation ? commencement of stem elongation (IR3) and normal irrigation (IRN), assigned to main plots and four levels of fertilizers, no fertilizer (FCo), 100 % FCh (100 % chemical fertilizer), seed inoculation by Pseudomonas putida (FBi), 50 % FCh ? FBi, assigned to subplots. The maximum forage yield was obtained at IRN, which followed a decreasing trend as the number of irrigations decreased. The best phosphorous fertilizer treatments affecting forage yield were 100 % FCh and 50 % FCh ? FBi in sequence. As the water stress increased, in vitro dry matter digestibility (IVDMD), metabolizable energy, and protein yield followed a decreasing trend while in the same situation the crude protein, water soluble carbohydrates, acid detergent fiber, and ash content followed an increasing trend.