基于稻田控水减排的氮肥运筹试验研究

为改善江汉平原地区稻田水肥管理措施,采用田间小区试验,研究了常规淹灌(CF)和浅灌深蓄(SIDS)条件下,农民习惯施肥(FFP)、30%尿素+70%控释参混肥(30%N+70%CRF)和优化减氮施肥(OPT-N)对水稻各生育阶段稻田氮磷流失特征、养分吸收和土壤养分积累的影响。结果表明:与CF处理相比,SIDS处理田间灌溉水量、总用水量、径流量和渗漏量分别降低41.7%,18.5%,45.8%和21.9%,降雨利用率增加16.2%,TN和TP径流流失量分别降低32.6%~35.9%和36.4%~53.1%,渗漏流失量分别降低22.8%~32.0%和16.2%~33.3%,水稻返青期—拔节孕穗期分别占稻田氮磷径流和渗漏流失总量的70%以上。30%N+70%CRF处理、OPT-N处理较FFP处理,TN径流流失量分别降低19.7%~29.2%,15.1%~25.2%,渗漏流失量分别降低25.4%~51.7%,20.9%~26.4%,TP渗漏流失量分别降低18.4%~24.5%,20.4%~31.6%,但TP径流流失量差别很小。从水稻养分吸收和土壤养分积累来看,SIDS处理实际产量相对CF处理可增产4.4%,但对0—40cm土层氮磷养分累积影响不大,30%N+70%CRF处理和OPT-N处理相对FFP处理可增产5.6%和0.4%,且0—20cm土层速效态氮磷养分能维持在一个较高且相对稳定的水平。综上,浅灌深蓄结合30%N+70%CRF施用有利于稻田节水、减少氮磷流失、水稻增产以及土壤肥力改善。     

不同施肥处理对三峡库区柑橘园土壤氮磷淋失影响

在2017年8月利用原状土柱模拟淋溶试验对三峡库区秭归县柑橘园土壤的氮磷淋溶流失进行研究,探讨不同施肥处理对土壤氮、磷淋失的影响,为三峡库区农业面源污染的防控提供理论依据。试验设置6个处理,分别为不施肥处理(T0)、减量施肥(T1)、常量施肥(T2)、增量施肥(T3)、常量复合肥A施肥(T4)和常量复合肥B施肥(T5)。结果表明:(1)不同施肥处理下,柑橘园土壤淋滤液中总氮(TN)、总磷(TP)、硝态氮(NO_3~-—N)和铵态氮(NH_4~+—N)的淋溶浓度范围分别为37.16~163.07,0.61~6.69,27.54~79.38,2.37~7.10mg/L。(2)施肥量和施肥种类皆为土壤中氮磷淋溶的影响因素。在相同施肥种类下,土壤氮磷淋溶浓度随施肥量增加而显著增加,但施肥量高到一定程度后,淋溶浓度增长幅度会降低。在相同施氮量下,硝态氮的淋失受施肥种类影响最大,铵态氮最小。(3)在土壤淋滤液中,硝态氮为可溶性氮主要淋失形态,其淋失量占TN淋失量的比率为29.72%~46.18%,NH_4~+—N淋失量的比重为1.09%~2.05%。从研究结果推论,常量复合肥A施肥处理更有利于肥料氮向供植物吸收可溶性氮转化并降低施肥后土壤中氮素累积的风险。     

坡向与植物群落对水蚀风蚀交错带土壤有机碳氮的影响

以黄土高原北部水蚀风蚀交错带六道沟流域内的1个支沟为对象,通过植被调查和采样分析,研究了坡向和植物群落类型对土壤有机碳(SOC)、全氮(TN)含量、碳氮比(C/N)和有机碳氮密度(SOCD、TND)的影响。结果表明:(1)坡向对0—20cm土壤SOC和TN含量及0—60cm C/N均有显著影响。SOC、TN含量及C/N分别表现为:半阴坡半阳坡沟头半阴坡半阳坡=沟头及半阳坡半阴坡≥沟头的趋势;(2)植物群落对0—10cm SOC和TN含量及0—20cm C/N均有显著影响。半阴坡分布的3种豆科群落达乌里胡枝子、紫花苜蓿及白花草木樨间土壤碳氮差异不显著,但均显著高于禾本科的长芒草群落;半阳坡分布的达乌里胡枝子和紫花苜蓿群落SOC和TN含量相当,均显著高于茵陈蒿群落(菊科)和长芒草群落;沟头的达乌里胡枝子群落SOC、TN显著高于长芒草。豆科草本植物更有利于促进土壤碳氮的积累;(3)坡向主要影响表层0—20cm SOCD和TND,其对60cm剖面SOCD和TND贡献率分别为45%～55%和47%～53%。不同植物群落下土壤表层及整个剖面SOCD和TND均有显著差异。研究支沟内SOCD平均为2.13kg/m2,远低于黄土高原其他地区。上述结果对于水蚀风蚀交错带土壤碳氮储量的精确评估及植被合理建造有一定指导价值。     

不同浓度螯合剂和浸提时间对土壤磷素提取效果研究

为确定螯合剂活化土壤磷素的最佳浓度和最优浸提时间,参考水肥一体化技术,在室内浸提条件下,研究了不同浓度(0,0.05,0.1,0.25,0.5,1.0g/L)乙二胺四乙酸(EDTA)和柠檬酸螯合剂(pH=4)在不同浸提时间(1,12,24,48,72h)下对粮田、菜田土壤和有效磷被钝化后菜田土壤中磷素提取效果。结果表明:EDTA和柠檬酸在粮田土壤上对磷素提取中最佳条件为螯合剂浓度0.05g/L,浸提时间12h。EDTA和柠檬酸在菜田土壤、明矾钝化和混合钝化(明矾∶白云石为1∶1)菜田土壤上提取磷素的最佳条件为螯合剂浓度0.5g/L,浸提时间12h;而在白云石钝化土壤中则为螯合剂浓度0.5g/L,浸提时间1h。总体来看,柠檬酸的活化提取磷素效果优于EDTA,尤其是在采用明矾和白云石钝化的土壤上。     

Correlating phosphorus extracted by simple soil extraction methods with foliar phosphorus concentrations of Picea abies (L.) H. Karst. and Fagus sylvatica (L.)

Phosphorus (P) concentrations in needles and leaves of forest trees are declining in the last years in Europe. For a sustainable forest management the knowledge of site specific P nutrition/availability in forest soils is vital, but we are lacking verified simple methods for the estimation of plant available P. Within this study, four soil P extraction methods [water ( ), double‐lactate (P_lac), citric acid (P_cit), and sodium bicarbonate ( )], as well as total P content of the soil (P_tot) were tested to investigate which method is best correlated with foliar P concentrations of spruce [Picea abies (L.) H. Karst.] and beech [Fagus sylvatica (L.)]. Mineral soil samples from 5 depth levels of 48 forest sites of the Bavarian sample set of the second National Forest Soil Inventory (BZE II) were stratified according to tree species (spruce and beech) and soil pH (pH < 6.2 and > 6.2), covering the whole range of P nutrition. The extractable amount of P per mass unit of soil increased in the order << P_lac < < P_cit, decreased with soil depth, and was higher in soils with pH < 6.2. Citric acid extracted up to 10% of P_tot in acidic soils. Whereas P_cit delivers adequate regression models for P nutrition in the case of spruce (R² up to 0.53) and beech (R² up to 0.58) for acidic soils, shows good results for spruce growing on acidic soils (R² up to 0.66) and for beech on soils with pH > 6.2 (R² up to 0.57). P_lac produces adequate models only for beech on high pH soils (R² up to 0.64), while did not produce acceptable regression models. P_tot seems suitable to explain the P nutrition status of beech on acidic (R² up to 0.62) and alkaline soils (R² up to 0.61). Highest R²s are obtained mostly in soil depths down to 40 cm. As and P_cit showed good results for both investigated tree species, they should be considered preferentially in future studies.     

Fate of phosphorus in soil during a long‐term fertilization experiment in Finland

Accumulation and depletion of soil phosphorus (P) was studied in a long‐term (37 y) field experiment in Southern Finland. The loam soil had a high pH (7.5–7.7) due to an earlier liming. Spring barley, spring wheat, oat, and ryegrass, grown in rotation, were annually fertilized with 0, 32, or 67 kg P ha^?1 y^?1 (P₀, P₁, and P₂K) and sufficient N. The average dry matter grain yield 2,600 kg ha^?1 of the P₀ plots increased by about 500 kg ha^?1 at P₁ treatment and another 600 kg ha^?1 by P₂K. Soil samples were collected in 1978 (beginning), 1995, 2005, and 2015. According to the Chang and Jackson sequential extraction, the P₂K and P₁ treatments increased the inorganic soil P by 732 and 32 kg P ha ^?1 in 37 years, respectively, while the P₀ plots were depleted by –459 kg P ha ^?1. The P₂K treatment increased all four P fractions, extracted with NH₄Cl (easily soluble), NH₄F (Al‐P), NaOH (Fe‐P), and H₂SO₄ (Ca‐P). Continuous depletion (P₀) decreased the NH₄Cl‐P and NH₄F‐P pools, NaOH‐P and H₂SO₄‐P pools remaining stable. None of the P pools changed significantly at P₁. The remarkable gap between the measured change and the balance for the P₂K and P₁ treatments cannot be explained solely by lateral soil movement, meaning that a significant proportion of the applied P was lost either in surface runoff or transported below the investigated depth of 40 cm. Despite large P applications, the degree of P saturation reached only 20% in the P₂K topsoil, assuming a 50% reactivity of Fe and Al oxides. As derived from sorption isotherms, a high EPC₀ (i.e., equilibrium P concentration at zero net P sorption or desorption) of 1.30 mg L^?1 had been built up in the P₂K treatment, while in the P₁ treatment EPC₀ (0.33 mg L^?1) had remained unchanged and P depletion (P₀) had caused a decrease to 0.12 mg L^?1. These results demonstrate that P sorption and desorption properties respond strongly to both P fertilization and null fertilization treatments and that in a long‐term field experiment only a low proportion of the residual fertilizer P can be recovered from soil.     

Morphological and physiological studies on densely branched lateral roots triggered by localized phosphate in Sesbania cannabina

Densely branched lateral roots (DBLRs) in Sesbania cannabina are formed in response to patchily distributed phosphorus (P) in volcanic soils. Little attention has been paid to morphological and physiological responses of DBLRs. Here, we investigated the relation between plant growth and DBLR development, enzymatic activities involved in P acquisition, and the influence of arbuscular mycorrhizal fungi (AMF), which contribute to P uptake, to clarify the function of DBLRs. We investigated DBLR development induced by localized application of P fertilizer and we compared the activities of phosphoenolpyruvate carboxylase (PEPCase) and acid phosphatase (APase) between DBLRs and non‐DBLRs. Additionally, plants were grown with or without AMF to investigate the effect of AMF colonization on the numbers of DBLRs and plant P uptake, and we compared AMF colonization between DBLRs and non‐DBLR roots. Secondary to quaternary lateral DBLRs were produced after the primary lateral roots passed near P fertilizer. P_i content per DBLR increased as DBLRs developed, promoting higher shoot growth. Under P deficiency, PEPCase and APase activities increased in non‐DBLR, but were significantly lower in DBLRs in the same plants. AMF inoculation changed the root system architecture by significantly decreasing the number of DBLRs, and AMF colonization was lower in DBLRs than in non‐DBLRs. Our results indicate that DBLR formation is a P‐coacquisition strategy of S. cannabina grown in P‐deficient andosolic soil. Roots that form DBLR are clearly different from non‐DBLR roots in morphological and biochemical response and AMF symbiosis.     

Long-term grazing exclusion influences arbuscular mycorrhizal fungi and their association with vegetation in typical steppe of Inner Mongolia,China

It is not certain that long-term grazing exclusion influences arbuscular mycorrhizal(AM) fungi and their association with steppe vegetation. In this study, soil and plant samples were collected from two sites of grazing exclusion since 1983(E83) and 1996(E96), and one site of free-grazing(FG) in the typical steppe of Xilinguole League, Inner Mongolia, China, and assayed for soil basic physicochemical properties, AM fungal parameters, aboveground biomass and shoot phosphorus(P) uptake as well. The results showed that long-term grazing exclusion of E83 and E96 led to less drastic seasonal changes and significant increases in spore density, hyphal length density and root colonization intensity of AM fungi and even soil alkaline phosphatase activity, by up to 300, 168, 110 and 102%, respectively, compared with those of FG site. In addition, the total aboveground biomass and shoot P uptake of E83 and E96 were 75–992% and 58–645%, respectively, higher than those of FG. Generally, the root colonization intensity, spore density, and hyphal length density of AM fungi were all positively correlated with the aboveground biomass and even shoot P uptake of plant. These results may imply that grazing exclusion play a critical role in increasing the growth of AM fungi, and subsequently, may increase plant P uptake and aboveground biomass production. Moreover, the spore density could sensitively reflect the impacts of long-term grazing exclusion on AM fungi since survival strategy of spores in soil.     

生物炭对土壤氮磷转化和流失的影响

针对土壤非点源污染产生的负面环境问题,近年来国内外的研究主要集中在有效减少农业生态系统中土壤氮磷的流失等方面。笔者综述了化学修复钝化剂生物炭对土壤中氮磷转化和流失影响的研究进展。生物炭凭借其特殊的材料结构和理化性质,影响着土壤中氮磷的存在。生物炭能够增加农作物对土壤中氮磷养分的吸附作用,提高作物的存活率和产量;改善土壤理化性质,起到减少土壤中氮磷养分的流失作用;降低田面水中氮磷的流失,抑制土壤中氮磷淋失,减少氨挥发损失,改善肥料效益。生物炭在促进氮磷吸收和吸附、促进氮磷形态转化和减少农田氮磷流失方面有巨大潜力,未来应加强其在土壤环境污染治理及其可持续性利用方面的研究。     

磷和不同价态硒对小麦硒吸收转运的影响

【目的】 研究小麦在施磷情况下对不同价态外源硒的吸收及转运规律,阐明小麦对硒吸收与转运的影响,分析不同价态硒在小麦体内的转运与分配。【方法】 采用盆栽试验,研究在施磷条件下硒酸盐和亚硒酸盐处理对小麦硒的吸收与转运。【结果】 低量硒酸盐处理中,低磷和高磷处理较不施磷处理的小麦硒肥利用率分别提高了96%和128%;高量硒酸盐处理中,低磷和高磷处理较不施磷处理的小麦硒肥利用率分别提高了78%和123%。低量亚硒酸盐和高量亚硒酸盐处理中,高磷处理较不施磷处理小麦硒肥利用率降低了50.7%和55.6%。施用硒酸盐时,高磷处理较不施磷处理小麦根、茎、叶及穗的硒含量分别增加了23.0%、17.0%、64.6%和62.1%;施亚硒酸盐时,高磷处理较不施磷处理小麦根、茎、叶及穗的硒含量分别降低了71.3%、72.1%、80.6%和73.8%。施用硒酸盐时,在不施硒、低硒及高硒条件下,高磷处理小麦植株硒富集系数较不施磷处理分别增加28.9%、60.6%和50.5%;施用亚硒酸盐时,在低硒及高硒条件下,高磷处理小麦植株硒富集系数较不施磷处理分别降低65.3%、72.3%。【结论】 磷素可以活化土壤中稳定态硒,提高了硒酸盐的生物有效性。施磷降低了土壤pH值,促使土壤中可溶态硒和可交换态硒转化成铁氧化物态硒和有机态硒,而铁氧化物态硒与有机态硒很难被作物吸收利用,造成当磷肥与亚硒酸盐配施时降低了作物对亚硒酸盐的吸收。