腐殖酸对磷在石灰性土壤中迁移的影响

When humic acid (HA) and phosphorus (P) fertilizer are simultaneously applied to soil, HA may affect the movement of P. A laboratory incubation experiment was conducted to quantify the effects of a commercial HA product co-applied with monocalcium phosphate (MCP) on the distance of P movement and the concentration of P in various forms at different distances from the P fertilizer application site in a calcareous soil from northern China. Fertilizer MCP (at a rate equivalent to 26.6 kg P ha-1 ) was applied alone or in combination with HA (at 254.8 kg HA ha-1 ) to the surface of soil packed in cylinders (150 mm high and 50 mm internal diameter), and then incubated at 320 g kg-1 moisture content for 7 and 28 d periods. Extraction and analysis of each 2 mm soil layer in columns showed that the addition of HA to MCP increased the distance of P movement and the concentrations of water-extractable P, acid-extractable P and Olsen P in soil. The addition of HA to MCP could enhance P availability by increasing the distance of P movement and the concentration of extractable P in soil surrounding the P fertilizer.     

Leaching and Transformation of Nitrogen Fertilizers in Soil After Application of N with Irrigation： A Soil Column Method

A soil column method was used to compare the effect of drip fertigation （the application of fertilizer through drip irrigation systems, DFI） on the leaching loss and transformation of urea-N in soil with that of surface fertilization combined with flood irrigation （SFI）, and to study the leaching loss and transformation of three kinds of nitrogen fertilizers （nitrate fertilizer, ammonium fertilizer, and urea fertilizer） in two contrasting soils after the fertigation. In comparison to SFI, DFI decreased leaching loss of urea-N from the soil and increased the mineral N （NH4^＋-N ＋ NO3^--N） in the soil. The N leached from a clay loam soil ranged from 5.7% to 9.6% of the total N added as fertilizer, whereas for a sandy loam soil they ranged between 16.2% and 30.4%. Leaching losses of mineral N were higher when nitrate fertilizer was used compared to urea or ammonium fertilizer. Compared to the control （without urea addition）, on the first day when soils were fertigated with urea, there were increases in NH4^＋-N in the soils. This confirmed the rapid hydrolysis of urea in soil during fertigation. NH4^＋-N in soils reached a peak about 5 days after fertigation, and due to nitrification it began to decrease at day 10. After applying NH4^＋-N fertilizer and urea and during the incubation period, the mineral nitrogen in the soil decreased. This may be related to the occurrence of NH4^＋-N fixation or volatilization in the soil during the fertigation process.     

灌溉施用氮肥后氮素在土壤中的转化及淋失状况: 土柱模拟研究

A soil column method was used to compare the effect of drip fertigation (the application of fertilizer through drip irrigation systems, DFI) on the leaching loss and transformation of urea-N in soil with that of surface fertilization combined with flood irrigation (SFI), and to study the leaching loss and transformation of three kinds of nitrogen fertilizers (nitrate fertilizer, ammonium fertilizer, and urea fertilizer) in two contrasting soils after the fertigation. In comparison to SFI, DFI decreased leaching loss of urea-N from the soil and increased the mineral N (NH₄⁺-N + NO₃^--N) in the soil. The N leached from a clay loam soil ranged from 5.7% to 9.6% of the total N added as fertilizer, whereas for a sandy loam soil they ranged between 16.2% and 30.4%. Leaching losses of mineral N were higher when nitrate fertilizer was used compared to urea or ammonium fertilizer. Compared to the control (without urea addition), on the first day when soils were fertigated with urea, there were increases in NH₄⁺-N in the soils. This confirmed the rapid hydrolysis of urea in soil during fertigation. NH₄⁺-N in soils reached a peak about 5 days after fertigation, and due to nitrification it began to decrease at day 10. After applying NH₄⁺-N fertilizer and urea and during the incubation period, the mineral nitrogen in the soil decreased. This may be related to the occurrence of NH₄⁺-N fixation or volatilization in the soil during the fertigation process.     

长期施肥对华北平原一种潮土有机氮组成的影响

In order to illustrate the change of nitrogen （N） supply capacity after long-term application of manure and chemical fertilizer, as well as to properly manage soil fertility through fertilizer application under the soil-climatic conditions of the North China Plain, organic N forms were quantified in the topsoil with different manure and chemical fertilizer treatments in a 15-year fertilizer experiment in a Chinese calcareous alluvial soil. Soil total N （TN） and various organic N forms were significantly influenced by long-term application of chemical fertilizer and manure. TN, total hydrolysable N, acid-lnsoluble N, amino acid N and ammonium N in the soil increased significantly （P 〈 0.05） with increasing manure and fertilizer N rates, but were not influenced by increasing P rates. Also, application of manure or N fertilizer or P fertilizer did not significantly influence either the quantity of amino sugar N or its proportion of TN. Application of manure significantly increased （P 〈 0.05） hydrolysable unknown N, but adding N or P did not. In addition, application of manure or N fertilizer or P fertilizer did not significantly influence the proportions of different soil organic N forms.     

太湖水稻土麦季尿素氨挥发损失

Ammonia volatilization losses from urea applied as a basal fertilizer and a top dressing at tillering stage in a wheat field of Taihu Region, China, were measured with a micrometeorological technique. Urea as fertilizer was surface broadcast at 81 (low N) and 135 (high N) kg N ha-1 as basal at the 3-leaf stage of the wheat seedling on December 2002, and 54 (low N) and 90 (high N) kg N ha-1 as top dressing on February 2003. Ammonia volatilization losses occurred mainly in the first week after applying N fertilizer and mainly during the period after basal fertilizer application, which accounted for more than 80% of the total ammonia volatilization over the entire wheat growth period. Regression analysis showed that ammonia volatilization was affected mainly by pH and NH4^ -N concentration of the surface soil and air temperature.Ammonia volatilization flux was significantly correlated with pH and NH4^ -N concentration of the surface soil and with daily air average temperature and highest temperature. Thus, application of urea N fertilizer to wheat should consider the characteristics of ammonia volatilization in different periods of N application so as to reduce ammonia losses.     

黄绵土与淋溶土含水量与施肥方法对铵固定和肥料氮回收率的影响

Ammonium fixation and the effects of soil moisture and application methods on fertilizer N recovery were investigatedin two soils of Shaanxi Province, China, a Luvisol and an Entisol, through two experiments performed in the laboratoryand in a glass shelter, respectively, by using ammonium bicarbonate (NH4HCO3). The laboratory closed incubationbox experiment was conducted using the Luvisol to study NH fixation rate at soil moisture levels of 10.1%, 22.7% and 35.3% water filled pore space (WFPS). The fixed NH -N increased dramatically to 51% and 66%, 67% and 74%,and 82% and 85% 1, 2 and 36 h after fertilizer incorporation at moisture levels of 10.1% and 22.7% WFPS and 35.3% WFPS, respectively. The rapid NH fixation rates at all moisture levels could help prevent NH losses from ammonia volatilization. In the glass shelter pot experiment, N fertilizer was applied by either banding (in a concentrated strip)or incorporating (thoroughly mixing) with the Entisol and the Luvisol. An average of 74.2% of the added N fertilizerwas recovered 26 days after application to the Luvisol, while only 61.4% could be recovered from the Entisol, due tohigher NH fixation capacity of the Luvisol. The amount of fixed NH decreased with increasing WFPS. The amountof fixed NH in the incorporated fertilizer treatment was, oll average, 10% higher than that in the banded treatment.Higher NH fixation rates could prevent N loss and thus increase N recovery. The results from the Luvisol showed lowernitrogen recovery as soil moisture level increased, which could be explained by the fact that most of the fixed NH wasstill not released when the soil moisture level was low. When the fertilizer was incorporated into the soil, the recovery ofN increased, compared with the banded treatment, by an average of 26.2% in the Luvisol and 11.2% in the Entisol, whichimplied that when farmers applied fertilizer, it would be best to mix it well with the 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.     

共施磷酸二氢钙和硫酸铵对土壤中钾形态转化的影响

Soil potassium (K) deficiency has been increasing over recent decades as a result of higher inputs of N and P fertilizers concomitant with lower inputs of K fertilizers in China; however, the effects of interactions between N, P, and K of fertilizers on K status in soils have not been thoroughly investigated for optimizing N, P, and K fertilizer use effciency. The influence of ammonium sulfate (AS), monocalcium phosphate (MCP), and potassium chloride application on K fractions in three typical soils of China was evaluated during 90-d laboratory soil incubation. The presence of AS significantly altered the distribution of native and added K in soils, while addition of MCP did not significantly affected K equilibrium in most cases. Addition of AS significantly increased water-soluble K (WSK), decreased exchangeable K (EK) in almost all the soils except the paddy soil that contained considerable amounts of 2:1 type clay minerals with K added, retarded the formation of fixed K in the soils with K added, and suppressed the release of fixed K in the three soils without K added. These interactions might be expected to influence the K availability to plants when the soil was fertilized with AS. To improve K fertilizer use effciency, whether combined application of AS and K was to be recommended or avoided should depend on K status of the soil, soil properties, and cropping systems.     

基施磷肥对石灰性土壤上番茄产量的影响

A lysimeter experiment with undisturbed soil profiles was carried out to study nitrogen cycling and losses in a paddy soll with applications of coated urea and urea under a rice-wheat rotation system in the Taihu Lake region from 2001 to 2003. Treatments for rice and wheat included urea at conventional, 300 （rice） and 250 （wheat） kg N ha^-1, and reduced levels, 150 （rice） and 125 （wheat） kg N ha^-1, coated urea at two levels, 100 （rice） and 75 （wheat） kg N ha^-1, and 150 （rice） and 125 （wheat） kg N ha^-1, and a control with no nitrogen arranged in a completely randomized design. The results under two rice-wheat rotations showed that N losses through both NH3 volatilization and runoff in the coated urea treatments were much lower than those in the urea treatments. In the urea treatments N runoff losses were significantly （P 〈 0.001） positively correlated （r = 0.851） with applied N. N concentration in surface water increased rapidly to maximum two days after urea application and then decreased quickly. However, if there was no heavy rain within five days of fertilizer application, the likelihood of N loss by runoff was not high. As the treatments showed little difference in N loss via percolation, nitrate N in the groundwater of the paddy fields was not directly related to N leaching. The total yield of the two rice-wheat rotations in the treatment of coated urea at 50% conventional level was higher than that in the treatment of urea at the conventional level. Thus, coated urea was more favorable to rice production and environmental protection than urea.     

Evaluation of Methods for Control of Ammonia Volatilization from Surface-Applied Nitrogen Fertilizers to Sugarcane Trash in North Queensland

Micrometeorological and microplot experiments were conducted in the field of freshly harvested green cane in Queensland,Australia.Results showed that high ammonia loss of fertilizer N could occur under relatively dry conditions when urea or commercial product of mixture of urea and muriate of potash were applied to the surface of sugarcane trash.The moisture content in the trash and the pH of fertilizer were two important factors controlling the processes of urea hydrolysis and ammonia volatilization.Most of the N in the soil was transformed to the nitratel-nitrite from after 70 days of fertilizer application.No significant leaching was found.Urea-free N fertilizers had higher N recoveries compared to urea-containing fertilizers.     

Soil pH Changes from Fertilizer Site as Affected by Application of Monocalcium Phosphate and Potassium Chloride

A laboratory incubation experiment using soil columns was conducted to study the effects of monocalcium phosphate (MCP) and potassium chloride (KCl) on soil pH changes in fertilizer microsites with two Chinese soils. Mixtures of two fertilizers at two rates (0 and 0.26 g per column) were added to the surface of soil cylinders. The results shown that both fertilizers significantly decreased soil pH after 7 d and 28 d, which declined with time and distance from fertilizer site. Compared with KCl alone, the soil pH decrease close to the fertilizer site induced by applied KCl was slowed down in the acidic red soil by MCP addition but was promoted in the calcareous soil. Compared with MCP alone, the application of KCl with MCP had greater effects of reducing pH in both soils. The magnitude and extent of soil pH changes were mostly contributed by KCl in the KCl plus MCP treatment.     

Effect of different biochar and fertilizer types on N2O and NO emissions

The use of biochar as soil improver and climate change mitigation strategy has gained much attention, although at present the effects of biochar on soil properties and greenhouse gas emissions are not completely understood. The objective of our incubation study was to investigate biochar's effect on N₂O and NO emissions from an agricultural Luvisol upon fertilizer (urea, NH₄Cl or KNO₃) application. Seven biochar types were used, which were produced from four different feedstocks pyrolyzed at various temperatures. At the end of the experiment, after 14 days of incubation, soil nitrate concentrations were decreased upon biochar addition in all fertilizer treatments by 6–16%. Biochar application decreased both cumulative N₂O (52–84%) and NO (47–67%) emissions compared to a corresponding treatment without biochar after urea and nitrate fertilizer application, and only NO emissions after ammonium application. N₂O emissions were more decreased at high compared to low pyrolysis temperature.Several hypotheses for our observations exist, which were assessed against current literature and discussed thoroughly. In our study, the decreased N₂O and NO emissions are expected to be mediated by multiple interacting phenomena such as stimulated NH₃ volatilization, microbial N immobilization, non-electrostatic sorption of NH₄⁺ and NO₃⁻, and biochar pH effects.     

Reducing ammonia loss from urea and improving soil-exchangeable ammonium retention through mixing triple superphosphate, humic acid and zeolite

Ammonia losses from soil following fertilization with urea may be large. This laboratory study compared the effect of four different, urea–triple superphosphate (TSP)–humic acid–zeolite, mixtures on NH₃ loss, and soil ammonium and nitrate contents, with loss from surface‐applied urea without additives. The soil was a sandy clay loam Typic Kandiudult (Bungor Series). The mixtures significantly reduced NH₃ loss by between 32 and 61% compared with straight urea (46% N) with larger reductions with higher rates of humic acid (0.75 and 1 g kg^?1 of soil) and zeolite (0.75 and 1 g kg^?1 of soil). All the mixtures of acidic P fertilizer, humic acid and zeolite with urea significantly increased soil NH₄ and NO₃ contents, increased soil‐exchangeable Ca, K and Mg, and benefited the formation of NH₄ over NH₃ compared with urea without additives. The increase in soil‐exchangeable cations, and temporary reduction of soil pH may have retarded urea hydrolysis in the microsite immediately around the fertilizer. It may be possible to improve the efficiency of urea surface‐applied to high value crops by the addition of TSP, humic acid and zeolite.     

NH4+对K+在土壤肥际微域中迁移和转化的影响

NH4^＋和K^＋共施在农田施肥中是很普遍的现象,研究它们共施后二者在土壤中的交互作用对指导施肥具有重要意义。采用室内土柱实验研究了共施条件下NH4^＋对K^＋在红壤和潮土肥际微域中的迁移和形态转化的影响,供试肥料为NH4Cl和KCl。试验结果表明,与单施K^＋相比,共施NH4^＋没有改变肥料钾在红壤和潮土中的迁移距离,但提高了肥际微域中的水溶性钾含量;在靠近施肥点附近,NH4^＋的施用减少了土壤交换性钾含量,这种作用在潮土中的表现不如在红壤中明显;与单施KCl相比,共施NH4Cl明显降低了施肥点附近土壤微域内的非交换性钾含量。研究结果表明,共施NH4Cl减少了土壤晶格对钾离子的固定,增加了钾的淋溶风险。     

控释尿素减施对双季稻田土壤剖面养分分布特征的影响

为探讨双季稻田控释尿素施用对养分在土壤剖面的垂直分布与迁移的影响,通过长期田间定位试验,研究比较普通尿素(U)和控释尿素(CRU)减施稻田剖面的养分累积和分布。结果表明:随着土层深度的增加,土壤全氮、NO_3~-—N、有机质、全磷、速效磷和全钾含量呈下降趋势,NH_4~+—N含量先下降后升高,速效钾含量呈上升趋势,土壤pH升高且趋于稳定。施肥会降低0—20cm土层pH和速效钾含量。与U处理相比,0—20cm土层CRU处理全氮含量提高7.72%~19.45%,且随着施N量的增加呈上升趋势;40—60cm土层CRU处理NH_4~+—N含量降低6.99%~19.23%。施用CRU可以有效降低土层NH_4~+—N向下淋溶,提高0—40cm土层全氮和NO_3~-—N含量,避免土壤N素流失。施用CRU对不同深度土层有机质、速效磷、全磷、速效钾、全钾和pH的影响不显著,但减量过大会导致有机质降低。CRU减量10%~20%处理显著提高双季稻成熟期N、P、K的吸收量。相关分析表明,不同用量控释尿素处理早、晚稻成熟期N、P、K吸收量与籽粒产量均呈显著正相关。总之,CRU处理有效地控制N素向下淋溶,减少因N肥施用带来的潜在面源污染,而CRU减施可更好地维持和提高土壤的养分水平和肥力,促进养分累积,实现生态与经济效益的双赢。     

磷在红壤肥际微域中的迁移和转化

采用室内土柱实验研究了磷在红壤肥际微域中的迁移和形态转化。结果表明,相同施量的磷在7天和28天时的迁移距离相同,施用磷酸二氢钙(MCP)0 2g和0 5g时的迁移距离分别为1 4cm和2 0cm。磷在施肥7天内的迁移量较大,然后只发生少量迁移。迁移进入土壤的磷86 3%～94 2%被吸附固定,64 1%～72 2%仍以有效态存在。在迁移距离内,土壤水溶性磷、酸溶性磷和有效磷含量与距施肥点距离呈极显著直线负相关。施肥量对水溶性磷、酸溶性磷和有效磷在肥际微域中的含量分布有显著影响;但培养时间只对水溶性磷含量分布有显著影响。     

Influence of the nitrification inhibitor DMPP on the community composition of ammonia-oxidizing bacteria at microsites with increasing distance from the fertilizer zone

The effect of the nitrification inhibitor 3,4-dimethylpyrazole phosphate (DMPP) on N transformations and composition of ammonia-oxidizing bacteria (AOB) communities was investigated at the centimeter scale in a microcosm experiment under laboratory conditions. After 28 days, samples were collected from soil treated with urea or urea and DMPP at increasing distance from the fertilizer zone; this distance ranged from 0 to 5 cm in both horizontal and vertical directions. The results showed that DMPP application significantly increased soil pH and NH ₄ ⁺ -N and mineral N (NH ₄ ⁺ -N, NO ₃ ^? -N, and NO ₂ ^? -N) concentrations but decreased (NO ₃ ^? + NO ₂ ^? )-N concentration, and such effect was decreased by increasing the distance from the fertilizer zone. Fingerprint profiles of denaturing gradient gel electrophoresis showed that the number of bands decreased by increasing the distance from the fertilizer zone due to decreasing NH ₄ ⁺ -N concentrations in the urea treatment. Compared to urea applied alone, DMPP application increased NH ₄ ⁺ -N concentrations and decreased AOB diversity from 0 to 3 cm but promoted diversity from 3 to 5 cm distance from the fertilizer zone. A phylogenetic analysis showed that AOB communities were dominated by Nitrosospira cluster 3. Therefore, the nitrification inhibitor DMPP modified the composition of AOB communities by increasing the distance from the fertilizer zone and this probably was related to the changes in soil pH and inorganic N concentration.     

氮在紫色土中的移动和水稻氮素利用率的研究

利用养分渗漏池研究了紫色土中氮肥品种、用量对氮素移动、淋失和水稻氮肥利用率的影响。结果表明:淹水期间淋失的氮素基本形态是NH4+-N,主要分布在土壤表层,并随时间而下移;NH4+-N 淋失量与降雨量呈显著正相关;氯化铵促进了NH4+-N 的淋失,但其氮肥利用率比尿素高8 个百分点,说明水稻上可酌施含氯化肥;增施氮肥增加了NH4+-N 的淋失量,减少了氮肥利用率,建议水稻施氮控制在150kg/hm2。