Research On Drip Fertigation Effects Of N,P,K For Developing Poplar Plantation

In order to study the drip fertigation techniques for poplar plantation, the relationship between the volume, biomass and N, P, K accumulation of 1-4 years poplar and the tree height and DBH under the condition of drip fertigation in Daxing forest farm of Beijing was analyzed, and the influence of different N fertilization levels on the growth of poplar was also studied during the 2012-2014.The main results are as follows:1) This study measured the growth, biomass and N, P, K nutrient accumulation of 1-4 years poplar to do regression analysis and equation fitting with the tree height and DBH, got the tree height curve equation, individual volume equation, the optimal equation of biomass and N, P, K nutrient accumulation.2) The drip fertilization of N 30g/tree, P 15g/tree, K 20 g/tree can achieve 3m height increment, 3cm DBH increment and 3.1m3/hm2 volume increment.3) The drip fertilization of N 120g/tree, P 20g/tree, K 50g/tree can achieve 4m height increment, 5cm DBH increment and 17.7m3/hm2 volume increment.4) The drip fertilization of N 140g/tree, P 30g/tree, K 60g/tree can achieve 4m height increment, 4cm DBH increment and 33.97m3/hm2 volume increment.5)Under the drip fertigation, N 30g/tree, P 15g/tree, K 20g/tree is the optimal fertilization of marginal benefit for 2 years old poplar; N 120g/tree, P 20g/tree, K 50g/tree is the optimal fertilization of marginal benefit for 3 years old poplar, can achieve maximum marginal income 863.08 yuan/hm2; N 160g/tree, P 30g/tree, K 60g/tree is the optimal fertilization of marginal benefit for 4 years old poplar, can achieve maximum marginal income 1487.3 yuan/hm2.6) The N, P, K nutrients accumulation, absorption and nutrient use efficiency of poplar were increased with the increase of tree age under the drip fertigation. The demand of nutrients is N>K>P, but the nutrient use efficiency is P>K>N.With the increase of applying N fertilizer, N, P, K use efficiency are slightly increase first and then declined slightly.The highest N, P, K nutrient use efficiency of poplar 2-4 years fertilization are N fertilizer 110g/tree, 160g/tree, and 170g/tree; P fertilizer 15g/tree, 20g/tree,and 30g/tree; K fertilizer 20g/tree, 50g/tree and 60g/tree.7) Under the drip fertigation, during 110-140g/tree, with the increase of N fertilizer, promote the growth of the phosphorus-solubilizing bacteria, inhibit the growth of the ammonifying bacteria, but has no obvious effect on cellulose decomposing bacteria growth.And the activity of phosphatase, urease and sucrase were increased with the increase of N fertilizer during 110-140g/tree, but more than 140 g/tree can inhibit the activity of urease and sucrase, with the continuous increase of N fertilizer, phosphatase activity continues to increase, while the activity of urease and sucrase fell sharply.8)According to the demands of poplar growth for nutrients, making three kinds of fertilization schedule of 1-4 years poplar high-yield forest under drip irrigation for north sand of China, it contains the optimal growth fertilization schedule, the optimal nutrient use efficiency fertilization schedule, and the optimal marginal benefit fertilization schedule.The fertilization of 1-4 years optimal growth is N 10g/tree, 30g/tree, 120g/tree and 140g/tree; P 5g/tree, 15g/tree, 20g/tree and 30g/tree; K 10g/tree, 20g/tree, 50g/tree and 60g/tree.The fertilization of 1-4 years optimal nutrient use efficiency is N 10g/tree, 110g/tree, 160g/tree and 170g/tree;the fertilization of P and K is the same. The fertilization of 1-4 years optimal marginal benefit is N 10g/tree, 30g/tree, 120g/tree and 170g/tree;the fertilization of P and K is the same.It offers a variety of fertilization for poplar high-yield forest under drip irrigation, the Forest producer can choose the fertilization schedule according to their requirements and actual situation in the future.