Effect of Sowing Dates and Seed Rates on Growth and Yield of Different Wheat Varieties: A Review

Sowing time, seeding rate and variety are the key responsible among many other factors enhancing the growth and yield of wheat. Wheat is one of the most important leading crops of Afghanistan and the world. Despite higher yield potential the average yield of wheat in Afghanistan is very less than most of countries of the world. Besides other responsible factors for lower yield introduction of new high yielding potential varieties, optimum seeding rates and their adaptability with new environment are the most important factors which decide the growth, yield and quality of wheat. Changes of optimum temperature during vegetative or reproductive growth of wheat adversely affect the initiation and duration of crop in different pheno-phases and finally yield of wheat. Wheat as winter crop requires definite temperature and light for optimum growth. Too early sowing when temperature is above the optimum produce poor plants and even higher seeding rate cannot compensate low yield. Under late sown conditions, wheat faces low temperature in the earlier stage and high temperature in the later stages of the growing season and requires favorable moisture for better growth and development which causes yield reduction. At optimum temperature, early sowing with optimum plant population enhances the growth and nutrient uptake of wheat resulting in higher crop production. The optimum seeding rate depends on temperature, sowing date and type of varieties. The seed rate increases with delay in sowing due to poor plant stand, where higher seeding rate produces more plants in unit area resulting in higher intra-crop competition hereby affecting the yield and production cost. Similarly lower plant population produces lower grain yield due to higher vegetative growth and space wastages. Therefore to minimize the effect of temperature variation, proper sowing date, optimum plant population and varietal selection according to environmental conditions are the best noncash options to increase the growth, yield traits and yield of the wheat.