摘要
【目的】磷农学阈值是指导不同作物磷肥用量并获取最佳经济产量的重要依据,然而,不同地区不同的耕作制度、土壤类型、作物种类、p H、温湿度条件下,作物的磷农学阈值不同。明确小麦–玉米轮作体系下,典型潮土区小麦和玉米的磷农学阈值,并分析其差异。【方法】本研究基于"国家潮土土壤肥力与肥料效益长期监测站"25年的定位试验,选取氮、钾肥施用充足和磷肥用量不同的NK(不施磷肥)、NPK(施用氮磷钾化肥)、NPKM(氮磷钾化肥和有机肥配施)、1.5NPKM(高量氮磷钾化肥配施有机肥)、NPKS(氮磷钾化肥与玉米秸秆还田配施)5个处理的试验数据,使用米切里西指数模型(Mitscherlich exponential model)拟合小麦和玉米的Olsen-P农学阈值,并通过对比不同土壤磷水平下两种作物的磷吸收利用特性,分析其阈值不同的原因。【结果】获得最大相对产量的95%时,潮土区小麦Olsen-P农学阈值为13.1 mg/kg,玉米Olsen-P农学阈值为7.5 mg/kg。玉米Olsen-P农学阈值低于小麦主要原因:1)土壤磷水平较低时,小麦对磷缺乏更为敏感,而玉米可保持相对较强的吸磷能力,25年不施磷处理玉米吸磷量是小麦的1.4倍;2)土壤Olsen-P含量达到玉米阈值,而未能达到小麦阈值时,可保障玉米籽粒、茎秆及小麦籽粒正常生长对磷的需求,但小麦茎秆磷浓度仅能达到相对最大磷浓度的68.9%,严重影响了小麦的正常生长和获取较高产量的能力;土壤Olsen-P含量提高到小麦阈值后,小麦茎秆磷浓度提高到相对最大磷浓度的80.5%以上,进而可保障小麦获得较高的产量;3)土壤磷素养分充足时,小麦对磷的吸收量大于玉米,且主要是由于小麦茎秆磷浓度和吸磷量随土壤Olsen-P含量的增加而大幅度增加。【结论】小麦和玉米作为典型潮土区两种重要的粮食作物,Olsen-P农学阈值分别为13.1和7.5 mg/kg。由于两种作物的生理特性不同,小麦对磷素的吸收利用率较低,茎秆需要较高的土壤磷浓度维持正常生长,产量形成对磷养分需求更大。因此,小麦–玉米轮作体系下,小麦的磷农学阈值更高,小麦季所需土壤磷供应量大于玉米季。为增强磷肥利用效率,减少磷肥投入量和土壤中磷素的过量累积,玉米季磷肥使用量应适当小于小麦季。当土壤Olsen-P水平高于作物磷农学阈值后,减少或短时间停止施用磷肥并不会对作物产量有明显影响。
【Objectives】Critical soil P levels are important basis for guiding phosphate fertilizer rate and obtaining the best economic benefits for different crops, however, critical soil P values may vary among different crops because of different areas, farming systems, soil types, p H, temperature and humidity conditions. Critical values of soil Olsen-P between maize and wheat in a wheat-maize rotation system in typical fluvo-aquic soil area were determined and analyzed in this studay.【Methods】This study was based on a 25 year fertilization experiment on "National Long-term Monitoring Station of Fluvo-aquic Soil Fertility and Fertilizer Effects".Five fertilzation treatments were investigated: NK, NPK, NPK plus farmyard manure(NPKM), 1.5 times of application rates of N, P, K plus farmyard manure(1.5 NPKM) and N, P, K plus maize straw(NPKS). The critical values of soil Olsen-P for crop yields were calculated using the Mitscherlich exponential model, and the absorption and utilization characteristics of phosphorus in two crops under different soil phosphorus levels were compared.【Results】Correspond to 95% of the maximum predicted relative yields, the critical value of Olsen-P was 13.1 mg/kg for wheat and 7.5 mg/kg for maize. The critical value of Olsen-P for maize was lower than that for wheat, and the reasons were: 1) When the soil phosphorus level was low, wheat was more sensitive to the phosphorus deficiency, while maize could maintain a relatively strong ability to absorb phosphorus. Total phosphorus absorption for maize was 1.4 times of wheat in no P fertilization treatment for 25 years. 2) When the content of soil Olsen-P reached the critical value for maize and did not reach the critical value for wheat, the requirement of phosphorus for maize grain, maize straw and wheat grain could be ensured, but the P concentration of wheat straw could only reach 68.9% of the relative maximum P concentration, which seriously affected the normal growth and high yield formation of wheat. When the soil Olsen-P content was increased to the wheat critical value, the P concentration of wheat straw increased to 80.5% of the relative maximum P concentration, and the high yield of wheat could be ensured. 3) When there was adequate soil phosphorus nutrient, the amount of phosphorus absorbed by wheat was higher than that of maize, mainly because with the increase of soil Olsen-P content, the wheat straw P concentration and P uptake amount were greatly increased.【Conclusions】The critical values of Olsen-P for wheat and maize were 13.1 and 7.5 mg/kg respectively in the typical fluvo-aquic soil. Wheat was relatively less efficient than maize in the absorption and utilization of soil P. Wheat straw needed higher P concentration to maintain normal growth, and needed stronger soil phosphorus supply accordingly for high yield.
引文
[1]Wang B,Li J M,Ren Y,et al.Validation of a soil phosphorus accumulation model in the wheat-maize rotation production areas of China[J].Field Crops Research,2015,178:42-48.
[2]Johnston A E,Syers J K.Changes in understanding the behavior of soil and fertilizer phosphorus:implications for their efficient use in agriculture[C].International Fertiliser Society,2006.
[3]Mallarino A P,Blackmer A M.Comparison of methods for determining critical concentrations of soil test phosphorus for corn[J].Agronomy Journal,1992,84(5):850-856.
[4]曲均峰,李菊梅,徐明岗,等.长期不施肥条件下几种典型土壤全磷和Olsen-P的变化[J].植物营养与肥料学报,2008,14(1):90-98.Qu J F,Li J M,Xu M G,et al.Total-P and Olsen-P dynamics of long term experiment without fertilization[J].Plant Nutrition and Fertilizer Science,2008,14(1):90-98.
[5]刘恩科,赵秉强,胡昌浩,等.长期施氮、磷、钾化肥对玉米产量及土壤肥力的影响[J].植物营养与肥料学报,2007,13(5):789-794.Liu E K,Zhao B Q,Hu C H,et al.Effects of long-term nitrogen,phosphorus and potassium fertilizer applications on maize yield and soil fertility[J].Plant Nutrition and Fertilizer Science,2007,13(5):789-794.
[6]Johnston A E,Poulton P R,White R P.Plant-available soil phosphorus.Part II.The response of arable crops to Olsen P on a sandy clay loam and a silty clay loam[J].Soil Use and Management,2013,29(1):12-21.
[7]Poulton P R,Johnston A E,White R P.Plant-available soil phosphorus.Part I.The response of winter wheat and spring barley to Olsen P on a silty clay loam[J].Soil Use and Management,2013,29(1):4-11.
[8]Bai Z H,Li H G,Yang X Y,et al.The critical soil P levels for crop yield,soil fertility and environmental safety in different soil types[J].Plant and Soil,2013,372(1-2):27-37.
[9]席雪琴,孙本华,陈勇,等.鴥土区作物和土壤淋溶磷临界值研究及推荐施磷建议[J].中国土壤与肥料,2015,(6):34-40.Xi X Q,Sun B H,Chen Y,et al.Research of phosphorus critical value for crop yield and soil leaching and phosphorus fertilizer recommendation on an anthropogenic Loess soil area[J].Soil and Fertilizer Sciences in China,2015,(6):34-40.
[10]Shi L L,Shen M X,Lu C Y,et al.Soil phosphorus dynamic,balance and critical P values in long term fertilization experiment in Taihu Lake region,China[J].Journal of Integrative Agriculture,2015,14(12):2446-2455.
[11]Tang X,Ma Y,Hao X,et al.Determining critical values of soil Olsen-P for maize and winter wheat from long-term experiments in China[J].Plant and Soil,2009,323(1-2):143-151.
[12]Jordan-Meille L,Rub?k G H,Ehlert P A I,et al.An overview of fertilizer-P recommendations in Europe:soil testing,calibration and fertilizer recommendations[J].Soil Use and Management,2012,28(4):419-435.
[13]鲁如坤.土壤农业化学分析方法[M].北京:中国农业科技出版社,2000.Lu R K.Analytical methods for soil and agricultural chemistry[M].Beijing:China Agriculture Science and Technology Press,2000.
[14]Colomb B,Debaeke P,Jouany C,et al.Phosphorus management in low input stockless cropping systems:Crop and soil responses to contrasting P regimes in a 36-year experiment in southern France[J].European Journal of Agronomy,2007,26(2):154-165.
[15]Dodd J R,Mallarino A P.Soil-test phosphorus and crop grain yield responses to long-term phosphorus fertilization for corn-soybean rotations[J].Soil Science Society of America Journal,2005,69(4):1118-1128.
[16]Sharpley A N,Jones C A,Gray C,et al.A simplified soil and plant phosphorus model:II.Prediction of labile,organic,and sorbed phosphorus[J].Soil Science Society of America Journal,1984,48(4):805-809.
[17]Jackson G D,Kushnak G D,Carlson G R,et al.Correlation of the Olsen phosphorus soil test:Winter wheat response[J].Communications in Soil Science and Plant Analysis,1991,22(9-10):907-918.
[18]Zhang F,Shen J,Jing J,et al.Rhizosphere processes and management for improving nutrient use efficiency and crop productivity:implications for China[A].Xu J M,Huang P.Molecular environmental soil science at the interfaces in the Earth’s critical zone[A].Springer Berlin Heidelberg,2010:52-54.
[19]Neumann G,R?mheld V,Waisel Y,et al.Root-induced changes in the availability of nutrients in the rhizosphere[J].Cheminform,2003,34(4):617-649.
[20]Brancourt-Hulmel M,Doussinault G,Lecomte C,et al.Genetic improvement of agronomic traits of winter wheat cultivars released in France from 1946 to 1992[J].Crop Science,2003,43(1):37-45.
[21]Mallarino A P,Atia A M.Correlation of a resin membrane soil phosphorus test with corn yield and routine soil tests[J].Soil Science Society of America Journal,2005,69(1):266-272.
[22]Johnston A E,Lane P W,Mattingly G E G,et al.Effects of soil and fertilizer P on yields of potatoes,sugar beet,barley and winter wheat on a sandy clay loam soil at Saxmundam Suffolk[J].The Journal of Agricultural Science,1986,106(1):155-167.
[23]Bollons H M,Barraclough P B.Assessing the phosphorus status of winter wheat crops:inorganic orthophosphate in whole shoots[J].The Journal of Agricultural Science,1999,133(3):285-295.
[24]Barrow N J.Soil phosphate chemistry and the P-sparing effect of previous phosphate applications[J].Plant and Soil,2015,397(1-2):401-409.
[25]Saroa G S,Biswas C R,Vig A C.Phosphate utilization by maize under differential residual P fertility[J].Journal of Nuclear Agriculture and Biology,1991,19(4):221-226.
[26]Saroa G S,Biswas C R,Vig A C.Residual and applied P availability to wheat[J].Journal of Nuclear Agriculture and Biology,1992,21:221-226.
[27]Singh J,Brar B S,Sekhon B S,et al.Impact of long-term phosphorous fertilization on Olsen-P and grain yields in maize-wheat cropping sequence[J].Nutrient Cycling in Agroecosystems,2016,106(2):157-168.