مقارنة بعض األسمدة الفوسفاتية وطريقة أضافتها في إنتاج الذرة الصفراء فــي تربـة جبسيـة تحت نظام الري بـالرش المحوري

Abstract

A field experiment was conducted during spring season of 2001 in gypsiferous soil under sprinkler irrigation center pivot to study the efficiency of three sources of p – fertilizers on corn yieled , movement of p – fertilizer and corn root in the soil , availability of p and some micronutrients in the soil . The experiment involved seven treatment replicate of three in a complete randomized block design . The treatments were :- 1. Broadcasting of diammonium –phosphate (DAP) before sowing . 2. Broadcasting of triple super phosphate (TSP) before sowing . 3. Broadcasting of urea- phosphat (UP) before sowing . 4. Applying UP with sprinkler irrigation at sawing in one dose. 5. Applying UP with sprinkler irrigation in two equal doses , one at sowing and the other after 35 days from sowing . 6. Applying UP with sprinkler irrigation in three equal doses , at sowing other 35 days from sowing and at silking stage . All p fertilizer sources were added to give 160 kg p2o5 / ha . Nitrogen as urea and potassium sulfates were added to the all treatments at rates of 240 kg N / ha and 24 kg k2so4 / ha . , respectively . All nitrogen and potassium fertilizers were applied with sprinkler irrigation . Nitrogen added in 10 doses , started 14 days after sowing and potassium sulfate was added in two doses , one 40 days from sowing and the second at silking stage . At silking stage , leaf area , plant height , root depth and N , P , K uptake were measured . At the end of the experiment availability of p were measured at soil depths of 0-10 , 10 – 20 and 20 – 50 cm and some micrountrient ( Mn , Fe , Cu ) were measured at soil depth of 0 – 30 cm . The grain yield of corn were take from an area of 4 * 10 m2 . The results showed the following 1. All Broadcasted TSP , DAP and UP fertilizers have significantly increased corn grain yield , plant height , leaf area and N , P , K taken by plant . However , UP has showed superiority in increasing the above plant variables in comparison with Broadcasted TSP and DAP specially when UP added with sprinkler irrigation in more than one dose . 2. Depth and quantity of p movement in the soil were higher with applying UP in comparison with TSP , DAP and the depth of p movement increased with increasing UP doses applied during crop growth with sprinkler irrigation . 3. Highest p fertilizer and water use efficiency were obtained with applying UP with irrigation water . These results attributed mainly to the deep distribution of plant roots . 4. Using UP with irrigation water in two or three doses during plant growth resulted in highest Fe , Zn and Cu availability in the soil . 5. Highest corn grain yield was obtained at applying UP with irrigation water in three or two doses .