Effects of fertilization and irrigation on corn yields,p content of corn leaves,and available p in soil

Abstract

Experiments were conducted on Congaree loam at Orange, Virginia, in 1963, 1964, and 1965 to measure the response of corn to irrigation and to 3 levels of P. Rate of N was 140 kg/ha. Levels of P were 0, 37.5, and 75 kg/ha; while the rate of K. was 70 kg/ha. All micronutrients were applied in recommended amounts. Excellent corn silage and grain yields were obtained and there was no response to added V except for grain yields on irrigated plots. Cropping with corn, irrigation, and fertilization appeared to have little effect on the P content of the 0‐ to 15‐cm soil layer. Irrigation and P fertilization did not affect the P content of the corn leaves. Fractionation of P indicated appreciable amounts of A1‐P, Fe‐P, and Ca‐P to a depth of 140 cm with less Al‐P than the other forms.

Moisture extraction by the corn, as measured with Bouyoucos blocks, indicated that the corn was utilizing moisture to a depth of 120 cm during silking and tasseling. The corn roots, therefore, had access to appreciable amounts of P below the 0‐ to 15‐cm soil depth. Since there was essentially no change in the P content of the 0‐ to 15‐cm soil depth, the corn apparently was either utilizing most of its P from soil depths below 15 cm, or available P was being maintained at a fairly constant amount from the various forms in which it was found in the soil. This is in contrast to the usual situation in which plants utilize appreciable amounts of P from, the 0‐ to 15‐cm soil depth.     

Effect of Mg And Zn fertilization on soil test levels,ear leaf composition,and yields of corn in northern West Virginia

Abstract

A corn fertility study was conducted at two locations in northern West Virginia to determine the response of corn (Zea mays L.) to applied Mg and Zn on two soils testing low in Mg by the ammonium acetate and Baker tests and low in Zn by the Baker test. The study consisted of three rates of Mg (0, 112, and 224 kg/ha) and three rates of Zn (0, 3.36, and 6.72 kg/ha) applied in a factorial design. The soil at the Morgantown location was medium textured with a CEC of 22.4, and the soil at the Reedsville location was coarse textured with a CEC of 15.8. Yield responses to applied Mg were obtained only on the coarse textured soil at the Reedsville location where exchangeable Mg was less than 5% of the CEC and equilibrium Mg was less than 9.0 10 ^‐4M. No yield response to Zn was obtained at either location.     

Effect of foliar and soil applied zinc on soil test levels,herbage composition,and yields of alfalfa

Abstract

Forages in the Northeast generally do not contain enough Zn to meet the National Research Council (NRC) recommended allowance for dairy cattle (40 mg/kg Zn). A study was undertaken to determine if foliar or soil application of Zn could increase Zn levels in alfalfa herbage to the NRC recommended allowance.

Alfalfa was treated with Zn by foliar applications of 0.34 and 0.68 kg/ha and soil application of 4.07 kg/ha. An untreated check was also included in the study. Average herbage Zn levels were 33.1 and 50.1 mg/kg for the low and high foliar applications, respectively. These levels were significantly higher than that of the check, 18.9 kg/ha. Average herbage Zn levels for the soil applied Zn treatment was 23.4 mg/kg. This level was also significantly higher than that of the check.

Although foliar Zn application significantly raised herbage Zn levels above those of the check, the results were erratic. The 40 mg/kg level was reached only one‐third of the time with the 0.34 kg/ha foliar application and two‐thirds of the time with the 0.68 kg/ha foliar application. Due to lower yields in comparison with cut 1, foliar application was more effective in raising herbage Zn levels in cuts 2 and 3. Foliar application of Zn does not appear to be a reliable means of insuring adequate herbage Zn levels for dairy cattle.     

长期施钾对红壤水稻土水稻产量及土壤钾素状况的影响

研究了长期定位施肥试验中连续27年（1981～2007）施用钾肥对水稻产量和土壤钾素状况的影响。本试验选择了其中5个处理:CK（不施肥）、NP（施氮、磷肥）、NPK（施氮、磷、钾肥）、NP+RS（施氮、磷肥和稻草）和NPK+RS（施氮、磷、钾肥和稻草）。结果表明,施钾能明显提高水稻产量,施钾肥的NPK和NPK+RS处理27年的早稻平均产量分别比NP和NP+RS处理增加15.2%和10.9%;晚稻增产17.2%和9.1%;在27年54季水稻种植期间,不同施肥处理早、晚稻产量的变化趋势不同。CK、NP处理的早、晚稻产量随时间的推移呈负变化趋势,而NPK、NP+RS和NPK+RS处理的早、晚稻产量呈正变化趋势。施钾的NPK和NPK+RS处理不同土层中土壤全钾、缓效钾和速效钾含量均高于NP和NP+RS处理的相同土层;除NPK+RS处理外,其它各处理表观钾平衡均为负值,其中CK和NP处理钾的负平衡值最大。长期施用钾肥能提高水稻产量和维持土壤钾素肥力。     

Effect of magnesium fertilization on yield and leaf composition of tomato plants

Tomato plants were grown for 2 years at 4 different rates of Mg fertilization on a Princeton loamy sand at pH 4.8 with 29 kg exchangeable Mg/ha. Calcareous limestone was used to provide a pH treatment in the second year. Magnesium deficiency symptoms were observed on plants grown on plots having ≤ 38 kg/ha NH₄OAC‐extractable Mg. Application of 56 kg Mg/ha corrected Mg deficiency and produced a significant increase in yield. Application of calcitic limestone also produced significant yield increases, but did not affect the development of Mg deficiency symptoms. Tomato yield was increased 27.9% by Mg application and 17.7% by lime application. Highest tomato yield was obtained with application of 112 kg Mg/ha. Symptoms of Mg deficiency were observed when the Mg concentration in recently mature leaf tissue was in the 0.30 to 0.32% range. Magnesium concentration in leaf tissue increased linearly with increasing Mg rate. Leaf Mg concentration at various growth stages of the tomato plant was variable depending on Mg treatment. Magnesium fertilization rate bad little effect on Ca or K leaf concentrations. Application of Calcltic limestone increased leaf tissue Ca and reduced leaf tissue Mg and Mn concentrations.     

中国玉米土壤速效钾丰缺指标与适宜施钾量研究

对自20世纪80年代以来我国开展的玉米土壤速效钾丰缺指标与适宜施钾量研究进行了系统总结。结果表明,30年来我国玉米土壤速效钾丰缺指标出现了降低趋势;不同区域玉米土壤速效钾丰缺指标差异很大,缺钾处理相对产量90%的速效钾含量指标变动于75~215 mg/kg之间;我国玉米土壤速效钾丰缺指标研究存在许多空白区域;我国玉米土壤缺钾较为普遍,速效钾丰缺级别集中于级别较高的第2和3级,缺钾处理相对产量大多介于80%~100%之间;土壤养分丰缺指标研究的试验点数不宜过少,各试验点土壤养分含量分布不宜过于集中,丰缺指标高端和低端采用外推数据需谨慎,并应予以注明;适宜施钾量与土壤速效钾丰缺级别线性负相关,与目标产量线性正相关;当钾肥当季利用率为50%、目标产量为10.5 t/hm~2时,玉米土壤速效钾丰缺级别由高到低第1~7级的适宜施钾量分别为K2O 0、44、88、132、176、221和265 kg/hm~2。     

红壤蔗区土壤有效态钾的空间变异研究

应用地统计学方法分析了农场尺度的红壤蔗区土壤表层的土壤速效钾、缓效钾的空间分布结构。结果表明,研究区域内的土壤速效钾和缓效钾含量都存在极强的空间相关性,在整个区域的空间分布具有相似性。缓效钾的协同克立格法的插值精度高于普通克立格法。研究结果可为甘蔗的钾肥精准管理提供依据。     

Long‐term fertilization impacts on corn yields and soil organic matter on a clay‐loam soil in Northeast China

A long‐term fertilization experiment with monoculture corn (Zea mays L.) was established in 1980 on a clay‐loam soil (Black Soil in Chinese Soil Classification and Typic Halpudoll in USDA Soil Taxonomy) at Gongzhuling, Jilin Province, China. The experiment aimed to study the sustainability of grain‐corn production on this soil type with eight different nitrogen (N)‐, phosphorus (P)‐, and potassium (K)–mineral fertilizer combinations and three levels (0, 30, and 60 Mg ha^–1 y^–1) of farmyard manure (FYM). On average, FYM additions produced higher grain yields (7.78 and 8.03 Mg ha^–1) compared to the FYM0 (no farmyard application) treatments (5.67 Mg ha^–1). The application of N fertilizer (solely or in various combinations with P and K) in the FYM0 treatment resulted in substantial grain‐yield increases compared to the FYM0 control treatment (3.56 Mg ha^–1). However, the use of NP or NK did not yield in any significant additional effect on the corn yield compared to the use of N alone. The treatments involving P, K, and PK fertilizers resulted in an average 24% increase in yield over the FYM0 control. Over all FYM treatments, the effect of fertilization on corn yield was NPK > NP = NK = N > PK = P > K = control. Farmyard‐manure additions for 25 y increased soil organic‐matter (SOM) content by 3.8 g kg^–1 (13.6%) in the FYM1 treatments and by 7.8 g kg^–1 (27.8%) in the FYM2 treatments, compared to a 3.2 g kg^–1 decrease (11.4%) in the FYM0 treatments. Overall, the results suggest that mineral fertilizers can maintain high yields, but a combination of mineral fertilizers plus farmyard manure are needed to enhance soil organic‐matter levels in this soil type.     

设施蔬菜土壤剖面氮磷钾积累及对地下水的影响

针对设施栽培中传统施肥灌溉带来的养分浪费和环境污染问题,采集河北省定州市设施蔬菜、农田土样及相应的地下水样品,分析了不同设施蔬菜种植年限土壤剖面中速效养分的累积规律及地下水受硝酸盐污染的程度。结果表明:0～200cm和0～400cm设施土壤的速效养分累积均高于对照农田。低龄棚硝态氮、速效磷、速效钾及水溶性磷含量分别为377.2mg·kg-1、448.8mg·kg-1、1405.6mg·kg-1、30.6mg·kg-1,分别是对照农田的4.7倍、4.6倍、1.4倍和11.5倍;老龄棚硝态氮、速效磷、速效钾及水溶性磷含量分别为629.1mg·kg-1、555.0mg·kg-1、2567.1mg·kg-1、35.2mg·kg-1,分别为对照农田的6.4倍、16.3倍、2.7倍和12.0倍。设施土壤速效养分深层累积比例随棚龄增加而增加。设施蔬菜栽培区表层地下水(地下饮用水,20m)受硝态氮污染严重,超标率和严重超标率为39.3%和7.1%;而深层地下水(农田和大棚灌溉水,40m)硝态氮含量7.4mg·L-1和9.6mg·L-1,超标率分别为25.0%和37.5%,无严重超标水样。     

Effect of potassium fertilization on soil potassium pools and rice response in an intensive cropping system in China

In order to assess the changes in soil K pools as affected by K‐fertilizer application and the impact of the changes on K balance, grain yield, and K uptake, an experiment was conducted in Central Zhejiang Province, E China, in a continuous double‐cropping rice system. Two sites were selected: (1) the Agricultural Research Institute of Jinhua (ARI) where soil is calcareous and (2) the Shimen Research Farm (SM) where soil is acidic. Eight consecutive crops were grown (1997–2000) in ARI and five consecutive crops (1998–2000) at SM. Treatments included unfertilized control (CK) and three different fertilizer treatments (NP, NK, and NPK). Potassium extracted by ion‐exchange resin decreased from 26 mg kg^–1 to 5–10 mg kg^–1 after eight consecutive seasons of growth at the ARI site. Addition of 100 kg K ha^–1 for each rice crop was not enough to maintain initial K availability, especially in the calcareous soil at ARI site. In treatments with K, a small increase in readily available K was observed only in SM soil. The K extracted by HNO₃ also decreased significantly in the treatments without K addition and was increased slightly in the treatments with K application. In the NP treatment, the decrease in HNO₃‐K was several times greater than resin‐K, indicating that nonexchangeable K may be the major source of K supply to rice. Soil K depletion was greater for hybrid rice than for inbred rice, and this difference in K demand should be taken into account in developing fertilizer recommendations for irrigated rice.     

Effect of nitrogen fertilization, cropping and irrigation on soil air composition and nitrous oxide emission in a loamy clay

Most of the nitrous oxide (N₂O) in the atmosphere, thought to be involved in global warming, is emitted from soil. Although the main factors controlling the production of N₂O in soil are well known, we need more quantitative data on the interactions of soil and the environment in the soil that affect the emission. We therefore studied the effects of irrigation, cropping (fallow, barley with grass undersown) and N fertilization (unfertilized, 103 kg N ha^?1) on the composition of soil air and direct N₂O emission from soil (using the closed chamber method) in a factorial field experiment on a well‐structured loamy clay soil during 1 June?22 October 1993. The measurements were made weekly during the growing season and three times after harvesting. The composition of the soil air did not indicate severe anoxia in any treatment or combination of treatments, but the accumulation of N₂O in the soil air indicated that hypoxia was common. At the start of the irrigation the emissions were small, even though there was much ammonium and nitrate in the soil and therefore a potential for emission of N₂O produced by both nitrification and denitrification. Larger emissions occurred later. The largest emissions were found when 60–90% of the soil pore space was filled with water. Irrigation and fertilization with N both roughly doubled the cumulative N₂O emission. Growing a crop decreased it by a factor of 3–7. Most N₂O was lost from the irrigated fertilized soil under fallow (3.5 kg N ha^?1), and least from the unirrigated unfertilized soil under barley (0.1 kg N ha^?1).     

不同灌溉量对砂壤温室黄瓜土壤溶液氮浓度及氮淋洗的影响

为探讨不同灌水量下砂壤温室黄瓜土壤中氮浓度的变化特征,借助温室内称重式蒸渗仪试验平台,以直径20 cm蒸发皿的蒸发量(E_p)为灌水依据,设置了I1(K_(cp1):0.8)、I2(K_(cp2):1.0)和I3(K_(cp3):1.2)3种灌水水平,研究了黄瓜生育期内不同土层土壤溶液中氮浓度的动态变化及氮淋洗情况。结果表明,减少灌溉量增加了20和40 cm土层中的硝态氮浓度,降低了60 cm土层的硝态氮浓度。与处理I3相比,处理I2在20和40 cm土层中的硝态氮生育期平均浓度增加了75.59%和134.36%,60 cm土层的硝态氮生育期平均浓度降低了18.88%。不同灌溉量处理在各土层中铵态氮最大浓度仅为0.4 mg·L~(-1),其中20 cm土层铵态氮浓度具有和硝态氮相似的变化规律,而40和60 cm土层中各处理无明显差异。黄瓜季淋洗出90 cm土体的氮总量为56.08~203.13kg·hm~(-2),占总施氮量的9.02%~32.69%。相比处理I3,I2处理不仅具有最高的黄瓜产量,而且氮淋洗总量降低了49.16%(P0.05),灌溉水利用效率和氮肥偏生产力分别提高了39.24%(P0.05)和18.88%(P0.05)。综合考虑土壤中氮浓度、淋洗量及黄瓜产量等指标,I2处理(K_(cp2):1.0)为供试条件下较优灌溉量。     

Effect of optimal irrigation,different fertilization,and reduced tillage on soil organic carbon storage and crop yields in the North China Plain

The objective was to evaluate the effect of different agricultural managements on soil organic C (SOC) storage and crop yields in the North China Plain (NCP). The study was conducted at five experimental stations. Different agricultural managements were designed, including optimal (OPT) and conventional (CON) irrigation and fertilization treatments, different amounts of fertilization application and residue‐return treatments, and different tillage practices. Compared to the CON treatment, SOC storage in the 1 m soil profile under the OPT treatment increased by 2 t ha^–1, 8 t ha^–1, and 4 t ha^–1 at Quzhou, Wuqiao, and Dongbeiwang sites, respectively. The annual increasing rate of SOC storages in the topsoil (0–30 cm) under the OPT treatments at Wuqiao (0.88 t ha^–1 y^–1), Quzhou (0.93 t ha^–1 y^–1), and Dongbeiwang (1.86 t ha^–1 y^–1) were higher than those in the CON treatments at Wuqiao (0.15 t ha^–1 y^–1), Quzhou (0.54 t ha^–1 y^–1), and Dongbeiwang (0.28 t ha^–1 y^–1), but the difference of grain yields between the two treatments was not significant. The SOC storage in 1 m soil profile in the no‐tillage treatment with standing residue return (NT1) at Luancheng increased by 5 t ha^–1 and 7 t ha^–1 compared with rotary‐tillage (RT) and conventional‐tillage (CT) treatments, respectively, but the crop yield under no‐tillage treatment was the lowest. While at Quzhou site, it increased by 3 t ha^–1 in the top 40 cm soil under the NT treatment compared to the CT treatment. The annual increasing rate of SOC storage in the top 30 cm under NT treatment was also the highest (1.08 t ha^–1 y^–1 at Luancheng, 1.86 t ha^–1 y^–1 at Quzhou), compared to the other tillage treatments. At Henghsui site, the combination of the highest fertilization application and highest residue‐return treatments got the highest SOC storage and the highest crop yields. We concluded that the agricultural management practices, such as optimal irrigation and fertilization treatment, the higher fertilization, residue return and RT, has significant impact on the SOC storage and agricultural sustainability in the NCP.     

Nutrient composition of leaves and fruit juice of grapevine as affected by soil and nitrogen fertilization

Effects of soil type and nitrogen (N) fertilizer–application rates on the nutrient composition of grapevine (Vitis vinifera L. cv. Riesling) leaves during a growing cycle were compared with the composition of the resulting grape juice. Grapevines were planted in 75 L containers that had been installed in a vineyard and filled with three different vineyard soils (loess, shell lime, and Keuper). Four typical levels of N fertilizer (40, 80, 120, and 160 kg N ha^–1) were applied. Elemental composition of mature leaves sampled seven times during the growing cycle as well as of the extracted grape juice was analyzed. The time of sampling affected all measured elements (C, N, Ca, K, P, Mg, S, Fe, Zn, Mn, and B) in the leaves. Nitrogen‐fertilizer rate affected the concentrations of all elements except Ca and Mg, while the soil type had significant effects on elemental composition of the leaves with the exception of N, B, and Ca. Soil type had a significant effect on K, S, Mn, and B in the grape juice. Increasing rates of N fertilizer increased C concentration in the grape juice significantly and affected its elemental composition similar to the effects in leaves. This may be explained with the role of leaves as the source for supplying the grapes during ripening via phloem transport. Cluster analysis for the elemental composition of soils, leaves, and grape juice revealed no consistent relationships indicating that other soil characteristics in addition to the mineral concentration influence the elemental composition of grapevine leaves and grape juice.     

干旱区灌溉及施肥措施下棉田土壤的呼吸特征

为探讨干旱区不同灌溉方式及施肥措施对棉田土壤呼吸速率的影响及其与水热的关系,在新疆绿洲农田棉花生长季设滴灌和漫灌2种灌溉方式,每种灌溉方式设有机肥(OM)、氮磷钾化肥(NPK)、氮磷钾化肥与有机肥配施(NPK+OM)3种施肥处理,以不施肥处理为对照(CK),对不同灌溉方式及施肥措施下土壤呼吸速率及土壤温度、土壤含水率进行了测定和分析。结果表明,不同灌溉方式及施肥措施下,棉田土壤呼吸速率具有明显的季节变化特征,在7月中旬达到峰值,10月中旬降至最低;日变化呈单峰曲线,盛花期峰值出现在15:00～17:00,盛铃期峰值均出现在15:00,最低值均出现在04:00。滴灌各施肥处理平均土壤呼吸速率显著大于漫灌,施肥处理间平均土壤呼吸速率大小顺序为(NPK+OM)>OM>CK>NPK,灌溉与施肥互作条件下,滴灌方式下NPK+OM处理平均土壤呼吸速率最大。滴灌和漫灌方式下各施肥处理的温度敏感性系数(Q10值)平均值分别为2.03和2.43,不同年份漫灌Q10值均大于滴灌。不同灌溉方式及施肥措施下,用复合方程预测土壤呼吸速率的准确性较高,R2值均在0.64～0.72。综合考虑土壤温度和土壤含水率对土壤呼吸速率的影响,能够提高区域土壤呼吸作用研究的准确性。     

东北地区黑土、草甸土长期施钾对玉米产量及耕层土钾素形态的影响

本试验研究了东北三省代表性的草甸土、黑土上连续13年施用钾肥对玉米产量和耕层土壤钾素形态的影响。结果表明,施钾可明显增加玉米产量,辽宁、吉林、黑龙江三个定位点NPK1处理分别较对照(NP)处理增产10.2%、13.6%、17.5%,但钾肥量增大(NPK2处理)产量没有表现出同步提高。施用钾肥可增加土壤水溶性钾、非特殊吸附钾、特殊吸附钾的含量和在全钾中的比例;施钾量增大,含量和比例随之提高,处理之间表现为NPK2NPK1NP。NPK2处理均与NP呈显著差异,两个土层表现基本一致,但在2040.cm土层下处理之间差距缩小。施钾总体增加了非交换性钾、矿物钾和全钾含量的同时降低了矿物态钾在全钾中的比例,三省试点的土壤表现基本一致。随土层加深,各点相应处理的不同钾形态含量和比例变化不尽相同。全钾在黑、吉、辽三点随土层深度的变化分别表现为降低、持平、升高。     

施肥培肥措施对春玉米农田土壤氨挥发的影响

采用通气法进行不同秸秆还田方式、施肥时期和方法对春玉米农田土壤氨挥发影响的研究。结果表明,秸秆还田同秋季耕翻深施肥结合,可以大幅度减少春玉米农田土壤氨挥发损失。试验测定期间,春施肥各处理的田间土壤氨挥发总量较大且处理间有明显差异,特别是秸秆直接还田春施肥处理(S3)氨挥发量最高,达30.36kg/hm2,较不施肥处理多挥发26.91kg/hm2,田间氨挥发损失占到施N肥总量的17.94%;秋施肥各处理的田间土壤氨挥发总量介于5.57~6.92kg/hm2间,田间氨挥发损失仅占施N肥总量的0.28%~1.18%,各处理间差异甚微,氨挥发损失总量极低。春施肥同秋施肥处理间比较,田间土壤氨挥发总量也存在明显差异,以秸秆覆盖间(S2、A2)差异最小,为2.65kg/hm2,以秸秆直接还田间(S3、A3)差异最大,为25.58kg/hm2,氨挥发损失增加了1.77%~17.06%。     

猕猴桃不同果园土壤和叶片营养状况分析

以"金魁"猕猴桃为试材,分析了湖北宜昌雷家畈地区高中低产园及藤肿病园土壤和叶片营养状况,结果发现,高产园叶片Ca含量比其它果园高10%～17%,叶片Ca为影响猕猴桃产量的关键性因素,叶片Ca含量高则果园整体产量高;藤肿病发生严重的果园土壤有效Cu的含量为0.93 mg/kg,极显著低于其他果园;当地猕猴桃园土壤交换性Ca含量207.8～306.0 mg/kg,有效Fe含量1.98～3.00 mg/kg,处于缺乏状态;P和Cl元素含量丰富。土壤和叶片之间矿质元素有不同程度的相关,其中土壤与叶片之间Cl元素相关性极显著。     

Effect of soil heating on the dynamics of soil available nutrients in the rhizosphere

The effect of soil heating on the dynamics of soil available nutrients in the rhizosphere was evaluated. A pot experiment was carried out by using a rhizobox; a pot which enables to sample soils and soil solutions not only temporally with plant growth but also spatially depending on the distance from the root-accumulating compartment. The experiment consisted of 4 treatments; soils with or without heating treatment (150°C, 3 h), each of which was either planted with maize (Zea mays L.) or not. During the 17-d experiment, soil solutions at 0–2 mm from the root-accumulating compartment were collected 5 times. Soils depending on the distance from the root-accumulating compartment and plants were also collected after the experiment. The ionic concentrations of the soil solutions and soil water extracts, and the nutrient contents of plants were analyzed. Immediately after soil heating, the concentrations of cations, SO₄ ^2-, CI^-, water-soluble P, and water-soluble organic carbon increased significantly. With plant growth, the total ionic concentration in the rhizosphere soil solution increased for heated soil, whereas it decreased for unheated soil. The increase of the concentrations of cations and SO₄ ^2- in the rhizosphere of heated soil was appreciable, suggesting that the movement of cations such as Ca²⁺ and Mg²⁺ by mass flow was regulated by that of SO₄ ^2-. Moreover soil heating inhibited nitrification, resulting in the supply of N mainly in the form of NH₄ ⁺ within 10 mm from the root-accumulating compartment. As a result, the soil pH decreased in the rhizosphere of heated soil. The amount of nutrients absorbed by plants, on the other hand, did not change significantly by soil heating except for an increase of P uptake. The increase of P uptake could be explained not only by the immediate increase of the water-soluble P concentration but also by the dissolution of Ca-bound P and the hydrolysis of water-soluble organic P in the rhizosphere.     

灌溉水盐分组成对土壤水盐迁移参数的影响

淡水资源不足和盐渍化是干旱地区农业生产的限制因子。研究水盐迁移参数是水盐调控的重要目标。为此,该研究以甘肃省秦安县兴国镇果园土样为研究对象,采用水平土柱入渗法,探讨不同盐溶液(氯化钠、氯化钠和氯化镁、氯化钠和氯化钙、氯化钠和氯化钾)在矿化度均为3 g/L的条件下对土壤水分扩散率和盐分离子水平迁移的影响。结果表明:不同盐分组成的灌溉水质和含水率对土壤水分扩散率的影响均达极显著水平(P0.01)。在灌溉水矿化度均为3 g/L的条件下,氯化钠盐溶液传输水分的潜在能力最大,加入一定的复盐对水分的传导起到阻滞作用,阻滞能力的大小是:氯化钙氯化钾氯化镁。不同盐分组成的灌溉水对土壤碳酸氢根和硫酸根的水平迁移具有显著的影响(P0.05),对盐分、钙离子和钠离子水平迁移具有极显著的影响(P0.01)。入渗距离对土壤pH的影响以及灌溉水盐分组成对土壤钠吸附比的影响均达显著水平(P0.05)。灌溉水盐分组成对模型参数初始值和终止值有显著的影响,参数初始值和终止值均呈现:氯化钠氯化钠和氯化镁氯化钠和氯化钾氯化钠和氯化钙。因此,从微咸水利用和盐渍化土壤改良的角度考虑,在微咸水灌溉中加入一定量的钙制剂可抑制水分扩散和降低土壤盐分含量;从灌溉方法来看,需从地块的两端轮换灌溉可预防地块一端脱盐而另一端积盐的现象。这一研究结果对于指导干旱、半干旱地区微咸水利用具有重要的科学意义。