石伟(1995-),男,甘肃天水人,硕士研究生,主要从事土壤氮循环研究。E-mail:
红壤地区施入的磷肥很容易被吸附固定而留存于土壤中,降低磷肥利用效率,留存于土壤中的磷对土壤生态功能和作物养分供应的后续效应值得关注。基于旱地红壤长期施肥定位试验,探讨常规施肥处理(CK)以及短期施入不同磷肥量(P2O5,0、50、100、150和1 000 kg·hm–2)多年后土壤养分、土壤氮循环过程和作物产量的变化特征。通过多元统计分析方法探讨不同磷肥处理下,土壤全碳、全氮和微生物生物量碳和氮转化过程的潜在速率以及产量等因子间的相互关系及其与磷的后期效应的关系。结果表明,在短期投入高剂量磷肥(1 000 kg·hm–2,P1000)27年后,土壤全碳、全氮和微生物生物量碳与常规施肥处理相比无明显差异,但显著提高了土壤pH和氮循环相关过程速率,包括氮矿化速率(Nitrogen mineralization rate,Nmin)、固氮酶活性(Soil nitrogenase activity,SNA)、潜在硝化速率(Potential nitrification rate,PNR)(
The utilization efficiency of phosphorus fertilizer is generally low in agro-ecosystems as phosphorus is readily co-precipitated with iron and manganese oxyhydroxides, iron aluminides, or directly adsorbed to the soil minerals, particularly in the red soil ecosystem. Thus, understanding the subsequent effects of phosphorus retained in the soil on soil ecological function and crop nutrient supply is of significance to guide the management of phosphorus fertilization.
Based on a long-term fertilization experiment in red upland soil, this study investigated the effect of the conventional fertilization (CK) and short-term phosphorus fertilizer input (at rates of 0, 50, 100, 150 and 1 000 kg·hm–2, P2O5) on soil nutrients, soil nitrogen cycle process and crop yields after 27 years. We evaluated the relationship between these factors and the residual effect of phosphorus using the multivariate statistical analysis method.
Short-term P fertilizer addition at a high rate (1 000 kg·hm–2, P1000) had no significant effects on soil total carbon (TC), total nitrogen (TN) and microbial biomass (MBC) compared to the conventional fertilization treatment (CK). Also, it significantly increased soil pH, nitrogen mineralization rate (Nmin), soil nitrogenase activity (SNA), and potential nitrification rate (PNR) (
Our results reveal that the short-term application of a large amount of phosphorus fertilizer has significant positive effects on maintaining soil fertility, microbial activity, soil nitrogen cycle function activity and crop yield even after 27 years, owing to the promotion of soil pH and slow release of available phosphorus.
磷是植物生长必需的大量元素,也是限制生态系统生产力的主要因子[
土壤对磷的吸附遵循吸附平衡原理[
本研究以云南曲靖红壤长期磷后效定位观测试验样地为研究对象,研究了短期投入不同浓度梯度的磷肥多年后,对土壤养分、磷循环相关酶活性、土壤微生物生物量以及氮循环过程的影响,并利用主成分分析、聚类分析和冗余分析探讨了其间的相互关系,以期从土壤酶活性、土壤微生物功能活性等角度评价磷的后效,为揭示红壤磷的固定和解析机制,为农田施肥管理提供科学依据和指导。
研究区位于云南省曲靖市麒麟区越州镇(25º18´6.8"N,103º53´55.4"E),海拔1 906 m,年均温13~15℃,年降雨量900~1 000 mm。该地区属于低纬高原季风气候,土壤类型为老冲积母质发育的山原红壤[
长期定位试验始于1987年,共包括5个磷梯度处理:P0、P50、P100、P150、P1000,施磷量分别0、50、100、150、1 000 kg·hm–2(P2O5计),另设1个常规施肥处理(CK)。常规施肥处理三个小区重复,不同磷梯度处理一个小区重复,小区面积33.3 m2。自1987年种植玉米开始,P50、P100、P150和P1000处理分别施入对应剂量的过磷酸钙,连续施用6年后停施磷肥以观测后效。常规施肥处理每年施用磷肥120 kg·hm–2(过磷酸钙),同时配施与当地农田施肥水平一致的尿素(276 kg·hm–2·a–1)和30 t·hm–2·a–1的有机肥(农家肥)。有机肥中有机质含量约830 g·kg–1,全氮含量约22 g·kg–1,有效磷和速效钾含量分别约为6.1 g·kg–1和4.5 g·kg–1。有机肥作为底肥一次性穴施,尿素作为追肥,苗肥施30%,穗肥施70%。试验小区夏季种植玉米(4月中旬播种),品种均为当地推广的玉米杂交良种,冬季休耕。
土壤样品采集于2019年夏季(7月15日)和秋季(10月15日),分别代表了作物生长旺盛期和作物收获后期,在常规施肥处理每个小区五点法在两株玉米间采集0~20 cm的土壤,混合为一个土壤样品。不同磷梯度处理小区则沿3条平行线进行样品采集,每条平行线取3点混和为一个重复。样品于冰袋上运回实验室后过2 mm筛,一部分风干后用于测定土壤理化性质,另一部分储存在4 ℃的冰箱,用于测定生物化学活性指标。玉米产量由小区实测产量换算得到。由于不同磷梯度处理仅有一个小区重复,故本文选取了同一处理近三年(2017-2019年)的产量数据平均值作为该处理的产量重复。
土壤理化性质测定参考文献[
土壤呼吸速率(Soil respiration,SR)[
酸性磷酸酶(Acid phosphatase,ACP)活性的测定采用荧光法[
氮矿化速率(Nitrogen mineralization,Nmin)[
潜在硝化速率(Potential nitrification rate,PNR)的测定采用氯酸盐抑制法[
潜在N2O排放速率(Potential N2O emission rate,PN2O)和净N2O排放速率(Net N2O emission rate,NN2O)[
数据的单因素、双因素方差分析和差异显著性检验(Duncan,
土壤物理化学性质在不同处理间具有显著差异(
长期不同施肥处理下土壤化学性质
Soil chemical properties under different long-term fertilization treatment
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在夏季,NH4+-N含量在常规施肥和P0处理中最高(分别为11.49 mg·kg–1和9.90 mg·kg–1),P50、P100、P150处理中次之(7.83~8.99 mg·kg–1),P1000处理中最低(4.74 mg·kg–1)(
不同施肥处理下近三年(2017-2019)玉米平均产量无显著差异(3 828~4 164 kg·hm–2,
不同施肥处理下近三年(2017-2019年)玉米年平均产量(a)、不同因子对近三年玉米产量的随机森林预测(b)以及1992-2019年间的玉米产量(c)
Maize mean yield in recent three years(2017-2019)under different fertilization treatments(a), random forest regression between crop yield and different soil factors(b), and corn yield during 1992-2019(c)
土壤微生物生物量碳(MBC)在常规施肥处理中最高(31.34 µg·g–1),P150和P1000处理次之,P50和P100处理最低(
酸性磷酸酶(ACP)活性反映了土壤微生物对土壤磷的活化能力和磷供应能力,与土壤磷水平紧密相关。夏季,ACP活性在常规施肥处理中最高(96.08 nmol·h–1·g–1干土),P1000处理中最低(38.15 nmol·h–1·g–1干土,
不同磷处理下土壤酸性磷酸酶活性
Soil acid phosphatase activity under different phosphorus treatments
P1000处理土壤氮矿化速率(2.85 µg·d–1·g–1干土)显著高于其他处理(
不同磷处理对氮循环过程的影响
Nitrogen cycle process under different phosphorus treatments
与土壤氮矿化速率一致,夏季土壤硝化潜势(PNR)在P1000处理中最高,达1.62 µg·h–1·g–1干土,在P50、P100和P150次之(0.95~1.02 µg·h–1·g–1干土),在P0处理中最低(0.64 µg·h–1·g–1干土,
在夏季,土壤潜在N2O排放速率(PN2O)在P0处理中最低(0.34 µg·h–1·g–1干土,
对土壤呼吸、磷酸酶活性和氮循环相关过程(SNA,PNR,PN2O和NN2O)进行主成分分析,前两个主成分解释了69.93%的变异(
不同磷处理下土壤氮转化过程速率分布特征的主成分分析(a)和平均聚合聚类(方法:UPGMA)分析(b)
Principal component analysis(a)and cluster analysis(b)(UPGMA)for the potential rates of soil nitrogen transformation processes under different phosphorus treatments
Spearman相关分析表明,土壤氮循环过程、磷酸酶活性和土壤呼吸速率与土壤AP、pH、NH4+-N、NO3–-N等均具有极显著的相关性(
土壤微生物活性、非生物因子间的Spearman相关分析(a)和微生物活性的冗余分析(b)
Spearman correlation analysis between soil microbial activity and non-biological factors(a)and Redundancy analysis for microbial activity(b)
本研究表明,在短期内(6年)连续施加大量磷肥后,即使多年不再施磷肥,仍然可以将土壤肥力、pH维持在较高的水平,进而有益于土壤微生物活性和作物产量。戴茨华等[
酸性磷酸酶(ACP)活性反映了土壤微生物对土壤磷的活化能力和磷供应能力[
微生物既是土壤养分循环的执行者,也是土壤中有效养分的储备库,因而可以作为土壤养分状况和土壤质量的表征[
土壤矿化作用,生物固氮和硝化作用是土壤重要的氮素转化过程,决定中土壤中有效态氮的供应。本研究发现P1000处理中土壤氮矿化速率(Nmin)和固氮酶活性(SNA)均显著高于常规施肥处理和不施磷处理。与此类似,P1000处理中潜在硝化速率(PNR)也显著高于常规施肥处理和P0处理。表明短期大量磷添加可以在长时间尺度上促进红壤的有机氮矿化、固氮作用和硝化作用过程,表现出明显的磷后效。Chen等[
反硝化作用是农田土壤温室气体N2O排放的主要来源,对于全球变暖具有重要的贡献[
在酸性红壤中短期大量施用磷肥(1 000 kg·hm–2,P1000)多年后(长达27年),由于大量磷肥投入导致的土壤pH提升和磷的缓释效应,使得磷肥在提升土壤肥力、微生物活性、土壤氮循环功能活性以及维持产量方面表现出明显的后期效应。在酸性红壤中长期投入较高的磷肥后,应关注磷的残效及其对氮循环过程的影响。
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