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Pennisetum purpureum Schumacher.×P. glaucum (Linnaeus) R. Brown cv. Reyan No.4 is one of the new crop varieties that cultivated widely in Hainan recently years, but low yield due to extentive management.Using Pennisetum purpureum Schumacher. x P. glaucum (Linnaeus) R. Brown cv. Reyan No.4 as material, the nutrition regulation of kinggrass was studied by "3414" regression design, and the corresponding mathematical model was established with the basis of nitrogen, phosphorus and potassium in order to explore the best fertilization program of kinggrass. The main results showed as follow:(1) The order of the larger and medium contents at different organs of kinggrass were that root was K>N>S>P>Ca>Mg; stem wereK>N>Mg>Ca>P>S; leaf wasK>N>Ca>Mg>P>S; complete stool was K>N>Ca>Mg>P>S.The distribution order of the larger and medium contents at different organs of kinggrass were that nitrogen was leaf> stem> root; phosphorus was leaf> stem> root; potassium was stem> leaf> root; Calcium was leaf> stem> root; magnesium was stem> leaf> root; sulfur was leaf> stem> root.(2) The order of the medium and trace contents at different organs of kinggrass were that root wasFe>Mn>Mo>Zn>Cu; stem were Fe>Mn>Zn>Mo>Cu; leaf was Fe> Mn>Mo>Zn>C; complete stool was Fe>Mn>Mo>Zn>Cu.The distribution order of the trace at different organs of kinggrass were that ferrous was leaf> stem> root; manganese was leaf> stem> root; copper was root> leaf> stem; zinc was root> stem> leaf; molybdenum was root> leaf> stem.(3) The order of the nutrition constituent contents at different organs of kinggrass were that stem and leaf were No nitrogen extract content>Crude fibre content> ash content> Crude protein content> Crude fat content;The distribution order of the trace at different organs of kinggrass were that Crude protein content. Crude fat content, ash content and No nitrogen extract content were leaf> stem; Crude fibre content was stem> leaf..(4) The quantity of nitrogen, phosphorus, potassium, calcium, magnesium and sulfur needed for producing 1000 kg of grain was 1.82,0.36,3.04,0.74,0.49,0.22 kg respectively. The quantity of Fe, Mn, Cu, Zn, and Mo needed for producing 1000 kg of grain was 48.72,13.30,1.65,6.53,7.14 g respectively. The proportion of Fe, Mn, Cu, Zn, and Mo is 1.00:0.27:0.03:0.13:0.15.Dry matter accumulation of three times tationally cutting king grass is 541.60 g/strains.Total absorption proportion of macro-nutrients W (N):W (P2O5):W (K2O) is 1.00:0.20:2.09, nutrient uptake sequence of macro-nutrients are K> N> P. after First tationally cutting, absorption proportion of macro-nutrients W (N):W (P2O5):W (K2O) is 1.00:0.20:1.67. After the second tationally cutting, absorption proportion of macro-nutrients W (N) ratio:W (P2O5):W (K2O) is 1.00:0.19:2.65. After the third tationally cutting, absorption proportion of macro-nutrients W (N) ratio:W (P2O5):W (K2O) is 1.00:0.20:1.93.Absorption proportion after three times tationally cutting king grass of Secondary-nutrients W(Ca):W(Mg):W(S) is 3.58:2.81:1.00, nutrient uptake sequence of Secondary-nutrients are Ca>Mg>S. after First tationally cutting, absorption proportion of Secondary-nutrients W (Ca):W (Mg):W (S)= 3.35:2.20:1.00. After the second tationally cutting, absorption proportion of Secondary-nutrients W (N) ratio:W (Ca):W (Mg):W (S) = 4.75:2.61:1.00. After the third tationally cutting, absorption proportion of Secondary-nutrients W (N) ratio:W (P2O5):W (K2O) is W (Ca):W (Mg):W (S)= 2.71:3.42:1.00.(5)At 0 to 60 days, three times tationally cutting king grass has a similar keep rising nitrogen and potassium changing trend. Absorption curve of phosphorus element in king grass during determination time is quite gentle. Absorption of phosphorus element during first tationally cutting period reach maximum after 45 days then gradually declined, absorption curve of phosphorus elements during secondary and third tationally cutting period are both slow rising.During first tationally cutting period, absorption quantity of calcium, magnesium, sulfur in the king grass is gradually rising until 60 days. maximum absorption of magnesium can be reached in 45 days during the second tationally cutting period. maximum absorption of magnesium can be reached in 30 days during the third tationally cutting period. maximum absorption of magnesium and sulphur can be reached in 45 days during the second tationally cutting period.(6)In different tationally cutting period, king grass has a different absorption intensity on nutrition elements. During the first tationally cutting period, the maximum absorption of nitrogen element is in 45 to 60 days. During the second and third tationally cutting period, the maximum absorption of nitrogen element is in 15 days.The absorption of phosphorus elements in king grass change little. the maximum absorption of nitrogen element is 0-15 days. According to the nitrogen fertilization, Nitrogen should be fully utilized in a month after planting, phosphorus, potassium could be suitable to the supplement of king grass nutrients.During the first tationally cutting grass, the maximum absorption of calcium element is 30 to 45 days, during the second and third tationally cutting period, the maximum absorption of calcium element is 15 to 30 days. During the first and second tationally cutting grass, the maximum absorption of magnesium element is 30 to 45 days, during the third tationally cutting period, the maximum absorption of magnesium element is 15 to 30 days. During the first tationally cutting grass, the maximum absorption of sulfur element is 30 to 45 days, during the second and third tationally cutting period, the maximum absorption of sulfur element is 15 to 30 days.(7) The yield of kinggrass would be increased by nitrogen, phosphorus and potassium under proper level, but yield was decreased beyond the best level. The best combination for the highest yield was Urea 399.08kg/hm2, FCMP 224.40kg/hm2 and Potassium chloride 60.38kg/hm2, and yield was 385.0t/hm2, with the optimal N、P、K ratio being W(N):W(P2O5):W(K2O)=5.07:1.12:1.The best combination for obtaining maximum economic yield of kinggrass was Urea 413.1kg/hm2, FCMP 207.9 kg/hm2 and Potassium chloride 156.1 kg/hm2. with the ratio being W(N):W(P2O5):W(K2O)= 6.33:1.25:1. in the other word, the cost of Urea、FCMP、Potassium chloride was 822.1、415.8、10.41 yuan/hm2,and produced 384.90t/hm2,and output value was 57735 yuan/hm2,while profit was 56341 yuan/hm2.The kinggrass utilization rate of nitrogenous fertilizer was 16.47%, the utilization rate of phosphatic fertilizer was 4.75%, the utilization rate of potash fertilizer was 39.46%. Every form 100kg kinggrass needs Urea 2.37kg、FCMP 0.38kg、Potassium chloride 4.09kg.(8) The Crude protein content of kinggrass would be increased by nitrogen, phosphorus and potassium under proper level, but decreased beyond the best level. The best combination for obtaining maximum Crude protein content was Urea 304.73 kg/hm2, FCMP 495.00 kg/hm2, Potassium chloride 73.5 kg/hm2, which theoretic Crude protein content was 8.82%.(9) The Crude fat content of kinggrass would be increased by nitrogen, phosphorus and potassium under proper level, but decreased beyond the best level. The best combination for obtaining maximum Crude fat content was Urea 0.00 kg/hm2, FCMP O.OOkg/hm2, Potassium chloride 157.5 kg/hm2, which theoretic Crude fat content was 4.97%.(10) The Crude fibre content of cassava would be increased by nitrogen, phosphorus and potassium under proper level, but decreased beyond the best level and potassium reduce continue. The best combination for obtaining maximum Crude fibre content was Urea 0.00kg/hm2, FCMP 495.0 kg/hm2, Potassium chloride 0.0 kg/hm2, which theoretic Crude fibre content was22.15%.(11) The ash content of cassava would be increased by nitrogen, phosphorus and potassium under proper level, but decreased beyond the best level and potassium increace continue. The best combination for obtaining maximum ash content was Urea 0.00 kg/hm2, FCMP 495.00 kg/hm2, Potassium chloride 31.50 kg/hm2,which theoretic ash content was 12.21%.(12) The No nitrogen extract content of kinggrass would be increased by nitrogen, under proper level, but increased beyond the best level; be increased by phosphorus, under proper level, but decreased beyond the best level; be increased by potassium, the No nitrogen extract content increace continue.The best combination for obtaining maximum No nitrogen extract content was Urea 0.00 kg/hm2, FCMP 495.00 kg/hm2, Potassium chloride 0.00 kg/hm2, which theoretic No nitrogen extract content was 55.63%.
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