渗灌对番茄根系生长发育的影响

Four depth treatments of subsurface drip irrigation pipes were designated as 1) at 20, 2) 30 and 3) 40 cm depthsall with a drip-proof flumes underneath, and 4) at 30 cm without a drip-proof flume to investigate the responses of atomato root system to different technical parameters of subsurface drip irrigation in a glass greenhouse, to evaluate tomatogrowth as affected by subsurface drip irrigation, and to develop an integrated subsurface drip irrigation method for optimaltomato yield and water use in a glass greenhouse. Tomato seedlings were planted above the subsurface drip irrigationpipe. Most of the tomato roots in treatment 1 were found in the top 0-20 cm soil depth with weak root activity but withyield and water use efficiency (WUE) significantly less (P=0.05) than treatment 2; root activity and tomato yield weresignificantly higher (P=0.05) with treatment 3 compared to treatment 1; and with treatment 2 the tomato roots andshoots grew harmoniously with root activity, nutrient uptake, tomato yield and WUE significantly higher (P=0.05) oras high as the other treatments. These findings suggested that subsurface drip irrigation with pipes at 30 cm depth witha drip-proof flume placed underneath was best for tomato production in greenhouses. In addition, the irrigation intervalshould be about 7-8 days and the irrigation rate should be set to 225 m^3 ha^-1 per event.     

Dynamics of Soil Moisture and Salt Content After Infiltration of Saline Ice Meltwater in Saline-Sodic Soil Columns

Saline ice meltwater can be used for irrigation and leaching of salts in salt-affected soil regions.A laboratory experiment was conducted using soil columns to investigate the redistribution of soil moisture, salt and sodium adsorption ratio(SAR) in saline-sodic soil under the infiltration of saline ice meltwater.Soils were treated using saline water of three irrigation volumes(1 600, 2 400 and 3 200 mL) at four salinity levels.These four salinity levels included salt free(0 g L~(-1)), low salinity level(1.4 g L~(-1)), moderate salinity level(2.7 g L~(-1)) and high salinity level(4.1 g L~(-1)).The prepared saline water was frozen into ice, and then the ice was put on the surface of soil columns.After 96 h, the infiltration rate and soil moisture content of saline ice treatments were greater than those of salt-free ice treatments, increasing with the increase of ice salinity.Infiltration of saline ice meltwater increased soil moisture content in the upper layers for all treatments.Both salt contents and SAR values in the upper soil layers decreased in all saline ice treatments and were lower than those in salt-free ice treatment.However, this trend was reversed in the deeper(below 20 cm) soil layers.The highest desalting rate and lowest SAR were observed in high-salinity treatment under three irrigation volumes in the 0–15 cm soil layer,especially under irrigation volume of 2 400 mL.These results indicate that saline ice(0–20 cm) meltwater irrigation is beneficial to saline-sodic soil reclamation, and the best improvement effect would be achieved when using high-salinity ice under optimal irrigation volume.     

地膜覆盖滴灌棉田土壤上水分动态的数值模拟

Drip irrigation under plastic mulch has been widely applied in arid Northwest China as a water-saving irrigation technology.A comprehensive knowledge of the distribution and movement of soil water in root zone is essential for the design and management of irrigation regimes.Simulation models have been proved to be efcient methods for this purpose.In this study,the numerical model Hydrus -2D was used to simulate the temporal variations of soil water content in a drip irrigated cotton field under mulching.A concept of partitioning coefcient,calibrated to be 0.07,was introduced to describe the efect of plastic mulch on prevention of evaporation.The soil hydraulic parameters were optimized by inverse solution using the field data.At the optimized conditions,the model was used to predict soil water content for four field treatments.The agreements between the predictions and observations were evaluated using coefcient of determination (R2) and root mean square error (RMSE).The results suggested that the model fairly reproduced the variations in soil water content at all locations in four treatments,with R2 ranging from 0.582 to 0.826 and RMSE from 0.029 to 0.050 cm3 cm-3,indicating that the simulations agreed well with the observations.     

稻田系统管理措施对微生物生物量C、N、P的长期影响

A 12-year field experiment was conducted to investigate the effect of different tillage methods and fertil-ization systems on microbial biomass C,N and P of a gray fluvo-aguic soil in rice-based cropping system .Five fertilization treatments were designed under conventional tillae(CT) or on tillage(NT) system:no fertilizer(CK) ; chemical fertilizer only(CF) ; combining chemical fertilizer with pig manure(PM); combining chemical fertilizer with crop straw (CS) and fallow (F). The results showed that biomass C,N and P were enriched in the surface layer of no-tilled soil,whereas they distributed relatively evenly in the tilled soil,which might result from enrichment of crop resdue,organic manure and mineral fertilzer,and surficial developent of root systems under NT.Under the cultivation system NT had slightly greater biomass C,N and P at 0-5 cm depth ,significantly less biomass C,N and P at 5-15 cm depth ,less microbial biomass C,N and equivalent biomass P at 15-30 cm depth as compared to CT,indicating hat tillage was beneficial for the multiplication of organims in the plowed layer of soil.Under the fallow system,biomass C,N and P in the surface layer were significantly greater for NT than CT while their differences between the two tillage methods were neligible in the deeper layers.In the surface layer,biomass C,N and P in the soils amended with oranic manure combined with mineral fertilizers were significantly greater than those of the treatments only with mineral fertilizers and the control.Soils without fertilzer had the least biomass nutrient contents among the five fertilization treatments.Obviously,the long-term application of organic manure could maintain the higher activity of microorganisms in soils.The amounts of biomass C,N and P in the fallowed soils varied with the tillage methods;they were much greater under NT than under CT,especially in the surface layer,suggesting that the frequent plowing could decrease the content of organic matter in the surface layer of the fallowed soil.     

长期施肥和耕作管理对华北平原土壤肥力的影响

In the North China Plain, fertilizer management and tillage practices have been changing rapidly during the last three decades; however, the influences of long-term fertilizer applications and tillage systems on fertility of salt-affected soils have not been well understood under a winter wheat (Triticum aestivum L.)-maize (Zea mays L.) annual double cropping system. A field experiment was established in 1985 on a Cambosol at the Quzhou Experimental Station, China Agricultural University, to investigate the responses of soil fertility to fertilizer and tillage practices. The experiment was established as an orthogonal design with nine treatments of different tillage methods and/or fertilizer applications. In October 2001, composite soil samples were collected from the 0–20 and 20–40 cm layers and analyzed for soil fertility indices. The results showed that after 17 years of nitrogen (N) and phosphorous (P) fertilizer and straw applications, soil organic matter (SOM) in the top layer was increased significantly from 7.00 to 9.30–13.14 g kg-1 in the 0–20 cm layer and from 4.00 to 5.48–7.75 g kg-1 in the 20–40 cm layer. Soil total N (TN) was increased significantly from 0.37 and 0.22 to 0.79–1.11 and 0.61–0.73 g N kg-1 in the 0–20 and 20–40 cm layers, respectively, with N fertilizer application; however, there was no apparent effect of straw application on TN content. The amounts of soil total P (TP) and rapidly available P (RP) were increased significantly from 0.60 to 0.67–1.31 g kg-1 in the 0–20 cm layer and from 0.52 to 0.60–0.73 g kg-1 in the 20–40 cm layer with P fertilizer application, but were decreased with combined N and P fertilizer applications. The applications of N and P fertilizers significantly increased the crop yields, but decreased the rapidly available potassium (RK) in the soil. Straw return could only meet part of the crop potassium requirements. Our results also suggested that though some soil fertility parameters were maintained or enhanced under the long-term fertilizer and straw applications, careful soil quality monitoring was necessary as other nutrients could be depleted. Spreading straw on soil surface before tillage and leaving straw at soil surface without tillage were two advantageous practices to increase SOM accumulation in the surface layer. Plowing the soil broke aggregates and increased aeration of the soil, which led to enhanced organic matter mineralization.     

热带地区不同香蕉长期轮作体系对土壤微生物和生物化学性质的影响

Soil microbiological and biochemical properties under various field crop rotations such as grains, pastures and vegetables have been studied intensively under short-term period. However, there is limited information about the influence of banana-based rotations on soil organic C, total N(TN), microbial biomasses and enzyme activities under long-term crop rotations. A field experiment arranged in a randomized complete block design with three replicates was carried out at the Wanzhong Farm in Ledong(18?37′–18?38′N, 108?46′–108?48′E), Hainan Province, China, to compare the responses of these soil parameters to long-term(10-year) banana(Musa paradisiaca)-pineapple(Ananas) rotation(AB), banana-papaya(Carica) rotation(BB) and banana monoculture(CK) in a conventional tillage system in the Hainan Island. Soil p H, total organic C(TOC), dissolved organic C(DOC), TN, total P(TP) and available P(AP) were found to be significantly higher(P 0.01) in AB and BB than CK at 0–30 cm soil depth. Microbial biomass C(MBC) and N(MBN) were observed 18.0%–35.2% higher in AB and 8.6%–40.5% higher in BB than CK at 0–30 cm. The activities of urease(UA), invertase(IA), dehydrogenase(DA) and acid phosphatase(APA) showed a mean of 21.5%–59.6% increase in AB and 26.7%–66.1% increase in BB compared with CK at 0–30 cm. Higher p H, TOC and DOC at 0–10 and 10–20 cm than at 20–30 cm were obtained despite of the rotations. Soil MBC and MBN and activities of UA, IA and DA decreased markedly(P 0.01) with increasing soil depth in the different rotation soils as well as the monoculture soil. In general, soil microbial biomass and enzymatic activities were more sensitive to changes in banana-based rotations than soil chemical properties, and consequently they were well-established as early indicators of changes due to crop rotations in the tropics.     

Effect of Continuous Vegetable Cultivation on PhosphorusLevels of Fluvo-Aquic Soils

oil P status, inorganic P fractions, and P sorption properties were studied using sandy fluvo-aquic horticultural soils,which are high in organic matter content for vegetable production in comparison with a soil used for grain crop productionin Zhengzhou, Henan Province, China. P fractions, Olsen-P, and OM were determined at different depths in the soilprofile and sorption isotherm experiments were performed. Most P in excess of plant requirements accumulated in thetopsoil and decreased with soil depth. Total P, inorganic P, and OM concentrations increased with continued horticulturaluse.Olsen-P concentrations in the 0-20 cm depth of horticultural soils were 9 to 25 times higher than those of the graincrop soil. A linear transformation of the Langmuir equation showed that the P adsorption maximum (491.3 mg P kg^-1)and the maximum phosphate buffering capacity (162.1 L kg^-1) for 80-100 cm were greater in the grain crop soil than thehorticultural soils. Thus, the most immediate concern with excess P were in areas where heavy P fertilizer was used forvegetable crops and where soil P sorption capacities were low due to sandy soils and high organic matter content.     

不同农业土壤中有效磷的变化与磷平衡的关系

Maintaining soil phosphorus(P) at adequate levels for plant growth requires assessing how the long-term P balance(viz., the difference between P inputs and outputs) results in changes in soil test P. The hypothesis that routinely measured soil properties can help predict the conversion factor of P balance into Olsen P was tested at 39 sites in agricultural areas of the Mediterranean region in Spain. A set of soil samples from each site was analyzed for Olsen P, inorganic P(P extracted using 0.5 mol L~(-1) H_2SO_4), pseudototal P(P extracted using 0.5 mol L~(-1) H_2SO_4 following ignition at 550℃), and organic P(the difference between pseudototal P and inorganic P). Organic and Olsen P were uncorrelated in most of the 39 soil sets, which suggests that organic P content changed little with P inputs and outputs. The slopes of the regression lines of Olsen P against pseudototal and inorganic P, which were used as two different measures of the conversion factor, ranged widely(from 0.03 to 0.25 approximately), with their average values(about 0.10) being similar to those found in long-term experiments conducted in temperate areas. Neither conversion factor was significantly correlated with any routinely measured soil property; however, the conversion factor for inorganic P was significantly lower for calcareous soils than for noncalcareous soils. Our negative results suggest the need to isolate the influence of soil properties from that of management systems and environmental factors relating to P dynamics in future studies.     

Effects of Irrigation Patterns and Nitrogen Fertilization on Rice Yield and Microbial Community Structure in Paddy Soil

Water and nitrogen (N) are considered the most important factors affecting rice production and play vital roles in regulating soil microbial biomass, activity, and community. The effects of irrigation patterns and N fertilizer levels on the soil microbial community structure and yield of paddy rice were investigated in a pot experiment. The experiment was designed with four N levels of 0 (N0), 126 (N1), 157.5 (N2), and 210 kg N ha-1 (N3) under two irrigation patterns of continuous water-logging irrigation (WLI) and water-controlled irrigation (WCI). Phospholipid fatty acid (PLFA) analysis was conducted to track the dynamics of soil microbial communities at tillering, grain-filling, and maturity stages. The results showed that the maximums of grain yield, above-ground biomass, and total N uptake were all obtained in the N2 treatment under WCI. Similar variations in total PLFAs, as well as bacterial and fungal PLFAs, were found, with an increase from the tillering to the grain-filling stage and a decrease at the maturity stage except for actinomycetic PLFAs, which decreased continuously from the tillering to the maturity stage. A shift in composition of the microbial community at different stages of the plant growth was indicated by principal component analysis (PCA), in which the samples at the vegetative stage (tillering stage) were separated from those at the reproductive stage (grain-filling and maturity stages). Soil microbial biomass, measured as total PLFAs, was significantly higher under WCI than that under WLI mainly at the grain-filling stage, whereas the fungal PLFAs detected under WCI were significantly higher than those under WLI at the tillering, grain-filling, and maturity stages. The application of N fertilizer also significantly increased soil microbial biomass and the main microbial groups both under WLI and WCI conditions. The proper combination of irrigation management and N fertilizer level in this study was the N2 (157.5 kg N ha-1) treatment under the water-controlled irrigation pattern.     

聚合果属生物炭引起的咸水灌溉下土壤养分有效性和番茄生长变化

Thermally modified organic materials commonly known as biochar have gained popularity of being used as a soil amendment.Little information, however, is available on the role of biochar in alleviating the negative impacts of saline water on soil productivity and plant growth. This study, therefore, was conducted to investigate the effects of Conocarpus biochar(BC) and organic farm residues(FR) at different application rates of 0.0%(control), 4.0% and 8.0%(weight/weight) on yield and quality of tomatoes grown on a sandy soil under drip irrigation with saline or non-saline water. The availability of P, K, Fe, Mn, Zn and Cu to plants was also investigated. The results demonstrated clearly that addition of BC or FR increased the vegetative growth, yield and quality parameters in all irrigation treatments. It was found that salt stress adversely affected soil productivity, as indicated by the lower vegetative growth and yield components of tomato plants. However, this suppressing effect on the vegetative growth and yield tended to decline with application of FR or BC, especially at the high application rate and in the presence of biochar. Under saline irrigation system, for instance, the total tomato yield increased over the control by 14.0%–43.3% with BC and by 3.9%–35.6% with FR. These could be attributed to enhancement effects of FR or BC on soil properties, as indicated by increases in soil organic matter content and nutrient availability. Therefore, biochar may be effectively used as a soil amendment for enhancing the productivity of salt-affected sandy soils under arid conditions.     

不同灌溉方法对保护地土壤有机质及氮素影响的研究

分层采集连续7年分别用渗灌、滴灌和沟灌灌溉的保护地0～80cm土层土壤样品,测定有机质、全氮及无机态氮和有机态氮含量,研究灌溉方法对土壤氮素形态及其数量剖面分布的影响。结果表明,三种灌溉处理0～80cm剖面土壤有机质含量变化范围为8.47～36.48 g kg-1,渗灌与滴灌有机质剖面分布相似,二者与沟灌差异较大;沟灌除30～40cm层次有机质含量低于渗灌和滴灌外,其它层次有机质含量均高于渗灌和滴灌处理。土壤全氮含量变化范围为0.72～3.97 g kg-1,在0～20cm土层不同灌溉方法之间差异显著,渗灌最大,沟灌次之,滴灌最小。无机硝态氮、铵态氮含量的变化范围分别为19.16～1442.06 mg kg-1和0～15.28 mg kg-1,在0～20cm土层各处理之间差异较为明显,以渗灌最大,沟灌次之,滴灌最小。有机态氮含量的变化范围为683.79～2512.87 mg kg-1,各处理之间的差异主要表现在0～30cm土层,其中0～10cm土层以渗灌处理有机态氮含量最高、沟灌次之,滴灌最低,10～30cm沟灌处理有机态氮含量却高于渗灌和滴灌处理。     

灌溉方式对设施土壤总有机碳及其腐殖质组分的影响

通过13年连续的番茄栽培灌溉试验,分析了沟灌、滴灌和渗灌3种灌溉处理0—80cm土层土壤有机碳及其腐殖质组分(胡敏酸、富里酸、胡敏素等)含量,探讨了不同灌溉方法对温室土壤有机质变化的影响。结果表明:3种灌溉处理土壤总有机碳、腐殖质各组分含量剖面变化特征一致,均随土层加深而降低,且这一变化主要集中在0—50cm土层,50—80cm土层变化较小。土壤总有机碳及其组分各灌溉处理间差异明显,将土壤剖面分为0—20,20—80cm上、下2个层次,总体上总有机碳含量上层为渗灌沟灌滴灌,下层滴灌沟灌渗灌;腐殖酸含量上层滴灌沟灌渗灌,下层为渗灌滴灌沟灌;胡敏素上层为沟灌滴灌渗灌,下层为渗灌滴灌沟灌。滴灌处理既能使0—40cm土层土壤有机碳含量保持较高水平,土壤腐殖质含量又高于沟灌、渗灌处理,这对于提升设施土壤肥力水平、保证番茄养分供应是有利的。     

灌溉方法对保护地土壤有机氮组分及剖面分布的影响

用Bremner有机氮分组法测定了连续7年采用不同灌溉方法灌溉的保护地土壤各剖面层次有机氮组分含量。结果表明,土壤全氮及有机氮各组分含量均随土层深度的增加而降低,但有机氮各组分占全氮的比例随土层深度增加的变化却无明显规律。用3种灌溉方法灌溉,不同土层间土壤有机氮各组分含量的差异主要存在于0~50 cm土层,50 cm以下差异很小;相同土层,土壤有机态氮含量均以酸解氮为主,且酸解氮中各组分绝对含量和相对含量的大小排列顺序均为,未知态氮>氨态氮>氨基酸态氮>氨基糖态氮。在0~80 cm土层,土壤酸解氮占全氮的比例大多在58%~60%之间,只有渗灌处理0~10 cm,10~20 cm及沟灌处理0~10 cm土层酸解氮占全氮的比例较低,分别为34.21%,50.75%和48.02%;而非酸解氮占全氮的比例大多在32%~36%之间。3种灌溉方法相比较,除个别层次外,酸解氮中氨基酸态氮、氨基糖态氮及氨态氮占全氮的比例在各土层中滴灌和渗灌处理均高于沟灌处理,而酸解未知态氮和非酸解氮占全氮的比例则为沟灌处理高于滴灌和渗灌处理。     

灌溉方式对保护地土壤磷素淋失风险的影响

自连续12年以相同试验方案、不同灌溉方式进行灌溉试验的保护地采集土壤样品,对不同灌溉处理土壤磷素淋失风险进行评价,并对影响土壤磷素淋失临界值大小的因素进行了探讨。灌溉处理设滴灌、沟灌和渗灌三种灌溉方式,采样深度为0~80 cm。结果表明,0~20 cm沟灌、渗灌和滴灌处理土壤的磷素淋失临界值Olsen-P含量分别为59.44 mg kg-1、65.39 mg kg-1和68.57 mg kg-1;而20~40 cm层次的土壤淋失值分别为60.61 mg kg-1,66.8 mg kg-1和70.58 mg kg-1;40~80cm土层则无临界值存在。影响土壤磷素淋失临界值Olsen-P含量的主要因素有土壤pH和有机质、活性Fe、活性Al、有效磷含量;土壤pH值越大、有机质、活性铁、活性铝和Olsen-P含量越高,磷素淋失临界值越大。对三种灌溉处理表层土壤磷素淋失风险进行综合评价,其风险大小顺序为沟灌、渗灌和滴灌,这提示人们在保护地生产中要充分注意土壤磷素有效性,通过选择合理的灌溉方式、改善施肥技术以加强保护地土壤水肥管理,保证作物生产高效、优质和降低环境风险。     

保护地不同灌溉方法表层土壤pH小尺度的空间变异

基于保护地定位灌溉试验,采用经典统计学和地统计学的方法,以网格取样方式采集不同灌溉方法(沟灌、滴灌、渗灌)表层土壤,研究微尺度下土壤pH值的空间变异特征及空间分布。结果表明:经6年灌溉,沟灌处理pH显著降低,沟灌和滴灌0～5cm土层土壤pH表现为中等空间自相关,而其5～10cm和渗灌0～5cm和5~10cm的土壤pH表现为弱空间相关,水分的供给方式和数量影响土壤pH的空间变异。     

灌溉方法对保护地土壤有机氮矿化特性的影响

采用Stanford和Smith提出的长期间歇淋洗通气培养法,对连续7a采用渗灌、滴灌和沟灌灌溉,栽培番茄的保护地不同剖面层次土壤的有机氮矿化特点进行了研究。渗灌管为发汗式半软管,埋深为30cm;渗灌、滴灌和沟灌灌水方法及施肥、田间管理同当地农业生产。当20cm深处的土壤水吸力达到40kPa时开始灌水,渗灌和滴灌每次的灌水量是沟灌灌水量的1/2。试验结果表明,土壤矿化氮含量随着土层深度的增加而降低。从累积矿化氮量—时间曲线变化的趋势看,可将保护地土壤0～50cm剖面分为三个层次,其中渗灌与滴灌处理相似,为0～20cm、20～40cm和40～50cm土层,而沟灌处理则为0～30cm、30～40cm和40～50cm土层。保护地不同层次土壤有机氮的矿化可以用Twopool模型表达。比较不同灌溉处理,在0～10cm土层,易矿化有机氮含量(N1)表现为滴灌>沟灌>渗灌,易矿化有机氮矿化速率(k1)常数也以滴灌处理最大,说明滴灌更有利于表层土壤易矿化有机氮的形成。与渗灌和沟灌相比,长期使用滴灌灌溉有利于改善保护地土壤有机氮的品质。     

干旱区咸水滴灌土壤盐分的分布与积累特征

通过三年咸水灌溉田间试验,探讨了新疆干旱区膜下滴灌条件下,咸水灌溉后土壤中盐分的分布及积累特征。研究结果表明:膜下滴灌棉田持续利用咸水进行灌溉,土壤中盐分逐年增加,积盐程度随灌溉水盐度的增加而加重。地表滴灌土壤盐分的表聚明显;而地下滴灌在滴灌管上部土层盐分含量较高。与地表滴灌相比,地下滴灌的盐分会被淋洗到更深的土层。两种滴灌方式下,0￣100cm土壤平均盐度均逐年增加,且积累程度随灌溉水盐度增加而加重。在干旱区连续进行咸水灌溉,盐分的累积效应非常明显,如果不采取必要的洗盐措施,土壤中盐分最终会累积到危害作物生长的程度。     

垄沟耕作条件下滴灌冬小麦田间土壤水分的动态变化

试验在池栽条件下研究了滴灌与垄沟耕作条件下冬小麦田间土壤水分的动态变化。结果表明：滴灌对0～60cm土壤水分含量影响比较明显，由于受土壤蒸发和作物根系吸收水分的影响，0～30cm土壤水分含量在整个生育时期内变化最为剧烈，其次是30～60cm层次的土壤，90～120cm层次的土壤整个生育时期水分含量最为稳定。灌溉后土壤水分0～120cm土层中呈现“Z”型分布，且与垄作相比，灌溉对沟播处理各层次的影响更大。另外，通过对不同生育时期各个层次土壤水分含量的分析可以看出，冬小麦的灌浆期是其活跃的耗水期，其次是抽穗期。不灌溉处理的耗水深度主要集中在土壤下层，灌溉处理的耗水程度变化较复杂。与畦播处理相比较（见讨论部分），灌溉后沟播处理土壤水分上升最明显，垄作处理次之，畦播最小。灌溉一周后畦播土壤水分下降最快，垄作次之，沟播最小。而就灌溉后土壤水分运动而言，垄作与沟播处理快于畦播处理。     

Effect of irrigation methods on urea phosphate reactions in calcareous soils

Abstract

Urea phosphate (17–44–0) (UP) was injected in surface placed drip irrigation lines, subsurface placed drip irrigation lines (15 cm below soil surface), or band under furrow irrigation on a calcareous soil. In drip irrigation, UP was split in two applications, two weeks apart, to give a total rate of 50 kg P₂O₅/ha. The furrow rate was 100 kg P₂O₅/ha in a single application. Soil analysis one month after the first injection of UP showed high levels of available P (NaHCO₃ extractable) around the drip emitters. Considerable P mobility in the soil was detected within 20 cm from the emitters. Banding UP under the furrow did not leave any measurable levels of available P by the end of the experiment. Soil NO₃‐N levels were comparable in all fertilized irrigation treatments, and were higher than the levels under an unfertilized furrow. Soil pH was reduced by 0.5 units around the drip emitters, but no change was measurable under furrow irrigation. Soluble salts (ECe) were concentrated in the top 10 cm of the soil surface in all the fertilized irrigation methods. Split application of UP in subsurface drip irrigation provided the longest residual and best distribution of available P in a calcareous soil.     

不同灌溉方式对保护地土壤酸化特征的影响

自连续13a在同一地块以不同灌溉方式进行灌溉试验的保护地,分层采集沟灌、滴灌、渗灌3个处理0～60cm土层土壤样品,研究灌溉方式对土壤酸化特征的影响。结果表明,3种灌溉处理土壤活性酸度和交换性酸含量均随着土层加深而降低,各处理间土壤活性酸度在0～40cm土层差异明显,总体为沟灌>渗灌>滴灌;土壤交换性酸差异出现在0～30cm土层,为渗灌>沟灌>滴灌;土壤交换性Al3+随土层加深呈先增加后降低的变化趋势,且以滴灌含量最低。各处理土壤盐基饱和度(BS)随土层加深而增加,在0～30cm土层为滴灌>渗灌>沟灌。土壤pH与交换性酸、硝态氮含量呈极显著负相关,与盐基饱和度、特别是Ca2+饱和度呈极显著正相关;Al3+占交换性酸比例与有机质含量呈极显著负相关。总之,保护地土壤酸化与硝态氮含量、盐基饱和度、有机质含量关系密切;与沟灌和渗灌相比,滴灌更利于抑制土壤酸化。