冬小麦-夏玉米体系磷效率对鴥土磷素肥力的响应

Responses of phosphorus use efficiency to soil phosphorus fertility under winter wheat-summer maize cropping in loess soil

【目的】研究鴥土区冬小麦-夏玉米轮作体系磷肥利用效率(PUE)和土壤肥力(磷素)的关系,可以界定土壤磷素的最佳管理范围及合理施磷量,为实现作物高产和减少磷素损失提供理论依据。【方法】采取鴥土长期定位试验5个不同磷素水平的土壤,有效磷含量依次为3.90 (F1)、15.00 (F2)、23.60 (F3)、35.70 (F4)和50.00(F5) mg/kg进行盆栽试验,供试作物为小麦‘小偃22’和玉米‘郑单958’。每个磷素水平土壤上设置5个施磷量(P2O5 0、30、60、90、120 kg/hm^2)。作物成熟后,收获地上部所有植株,晒干、脱粒后测定地上部生物量、籽粒产量,籽粒和秸秆样品粉碎后测定其含磷量。作物收获后均匀采集盆内土样约50 g/盆,风干并混匀后分别过1 mm和0.15 mm筛,测定土壤速效磷和全磷含量。计算冬小麦-夏玉米种植体系磷肥利用效率与土壤磷素水平的关系。【结果】F1土壤增施磷肥可显著提高小麦和玉米的籽粒产量,与P0相比,所有施磷处理小麦增产52.2%～119.7%、玉米增产94.7%～212.7%;F2、F3、F4和F5土壤磷肥增产效果不显著。经过两季作物种植,与P0相比,F2土壤施磷60 kg/hm^2、120 kg/hm^2和F5土壤施磷120 kg/hm^2显著提高了全磷含量,其他磷水平土壤全磷含量无显著变化;F1、F2、F3、F4和F5土壤施磷处理的土壤速效磷含量分别增加了-4.08%～434.69%、26.49%～112.77%、6.74%～48.24%、4.07%～43.65%和-4.84%～28.29%。冬小麦磷肥利用效率(PUE)与土壤Olsen-P之间呈显著的正相关关系(P <0.05),P30、P60、P90和P120线性关系决定系数分别达到0.996、0.899、0.760和0.820。夏玉米PUE在P30下随土壤磷素水平的提高呈二次抛物线形式增加,据此可得出在Olsen-P为12.32 mg/kg时PUE达到100%,当土壤速效磷为33.63 mg/kg时PUE达到最大值155.24%;在P60、P90和P120时,PUE随土壤Olsen-P含量上升而直线增加,Olsen-P分别达到12.22 mg/kg、16.64 mg/kg和14.39 mg/kg后维持在一个水平。整个冬小麦-夏玉米体系PUE随土壤速效磷的变化趋势和夏玉米类似,冬小麦(P30)和夏玉米(P30)总施磷量为P2O5 60 kg/hm^2时,可算出土壤速效磷为17.97 mg/kg时PUE达到100%;当速效磷达到40.11 mg/kg时,PUE达到最大值131.51%。在同一磷素水平土壤上,随施磷量增加,小麦和玉米PUE均显著降低,尤其是施磷量高于60 kg/hm^2后。【结论】关中鴥土区冬小麦-夏玉米体系,小麦季土壤速效磷应大致控制在17～40 mg/kg范围内,玉米季土壤速效磷控制在13～34 mg/kg范围内进行管理;整个冬小麦-夏玉米体系将土壤速效磷大概控制在17～40 mg/kg范围内,总推荐施磷量为P2O5 60～120 kg/hm^2为宜。

[ Objectives ] The relationship between phosphorus use efficiency and soil phosphorus fertility is of great importance to quantify the optimum soil phosphorus level for the best management strategy of phosphorus resources. The judicious phosphorus management can help to achieve high crop production and meanwhile to minimize the potential risk of P Joss to environment. [ Methods ] Using wheat ＇Xiaoyan 22＇ and maize ＇Zhengdan 958＇ as tested crops, and use the loess soils subjected to diverse fertilizer treatments from a 25 yearslong-term experiment, we conducted a pot experiment with 5 sets of soils containing ascending Olsen-P values of 3.90, 15.00, 23.60, 35.70 and 50.00 mg/kg （labeled as F1, F2, F3, F4 and F5 in turn）. Five P205 rates of 0, 30, 60, 90 and 120 kg/hm2 were applied for each soil. After harvest, the crop grain yield and above ground biomass were weighed, plant samples were pulverized for P content and accumulation analysis; soil samples of 50 g/pot were collected and the total P and Olsen-P contents in soil were analyzed; the responses of PUE to soil Olsen-P levels under winter wheat-summer maize cropping system were estimated. [ Results ] Compared with P0, the application of phosphorus significantly increased the grain yield of winter wheat by 52.2%-119.7% and summer maize by 94.7%-212.7% in F1 soil, but showed no significant effects in the other soils. After two crops harvesting, no significant increases in soil total P content were observed in all the treatments except for at P2O5 rates of 60 kg/hm2, 120 kg/hm2 in F2 and 120 kg/hm2 in F5. However, soil Olsen-P contents were increased by -4.08%-434.69%, 26.49%-112.77%, 6.74%-48.24%, 4.07%-43.65% and -4.84%-28.29%, respectively, on soils of F1, F2, F3, F4 and F5 over the corresponding P0 treatments. At the P application rates of 30, 60, 90 and 120 kg/hm2, the PUE of wheat were significantly increased in linear with the increase of soil initial Olsen-P level （P 〈 0.05）, the coefficients of determination were 0.996, 0.899, 0.760 and 0.820, respectively. At P30, the PUE of maize was increased followed a pattern of parabola with the soil increase of initial Olsen-P, and the PUE reached 100% at the soil Olsen-P content of 12.32 mg/kg and its maximum of 155.24% appeared at soil Olsen-P of 33.63 mg/kg; at P60, P90 and P120, the PUE of maize increased significantly and linearly with the soil Olsen-P contents and reached its maximum value at Olsen-P of 12.22 mg/kg, 16.64 mg/kg and 14.39 mg/kg, respectively, and then kept a constant value. The soil Olsen-P dependent PUE for the entire winter wheat-summer maize cropping system was much like that of summer maize. The PUE reached 100% at the soil Olsen-P of 17.97 mg/kg at annual P application rate of 60 kg/hm2 （wheat 30 kg/hm2 and maize 30 kg/hm2） and the maximum value of PUE reached 131.51% at Olsen-P of 40.11 mg/kg. Under the same soil phosphorus level, the PUE of -wheat and maize decreased significantly with the increase of P application rate, especially when the P application rate was higher than P2O5 60 kg/hm2. [ Conclusions ] The optimum soil Olsen-P contents are from 17 mg/kg to 40 mg/kg for winter wheat, and from 13 mg/kg to 34 mg/kg for summer maize in the loess soil of Guanzhong area. From the viewpoint of the whole winter wheat-summer maize cropping system, the soil Olsen-P content should be maintained at the range of 17-40 mg/kg, and annual phosphorus application rate of P2O5 60-120 kg/hm2 was recommended.