8Crookston P K,,Treharne K J,Ludgord P,Ozbun J L.Responseof beans to shading. Crop Science . 1975
9Zhao D,Oosterhuis D M.Influence of shade on mineral nutrient status of field-grown cotton. Journal of Plant Nutrition . 1998
10Combell C. A,F Selles,et al.Factors influencing grain N concentration of hard red spring wheat in the semiarid prairie,Can. The Journal of Soil Science . 1997