Nitrogen Fertilizer Replacement Value of the Liquid Fraction of Separated Livestock Slurries Applied to Potatoes and Silage Maize

Separation of livestock slurries followed by reverse osmosis yields mineral concentrates (MCs) in which almost all nitrogen (N) is ammonium (NH₄)-N. The ability of MCs to substitute calcium ammonium nitrate (CAN), a common conventional mineral N fertilizer, was tested in two trials on a silty loam soil (ware potatoes, 2009 and 2010) and four trials on sandy soils (starch potatoes, 2009 and 2010; silage maize in 2010 and 2011). The N fertilizer replacement value (NFRV) of spring-injected MCs ranged from 72 to 84%, slightly less than their share of ammonium-N (90–100%). The fate of N that was apparently unavailable to crops was not fully disclosed, but there were indications that ammonia loss may have played a role.     

Effects of short‐term nitrogen supply from livestock manures and cover crops on silage maize production and nitrate leaching

Resource use efficiency requires a correct appreciation of the nitrogen (N) fertilizer replacement value (NFRV, percentage of total N applied) of manures. We assessed the NFRVs of the liquid fraction originating from separated pig slurry (MC), untreated pig slurry (PS), untreated cattle slurry (CS), the solid fraction from separated pig slurry (SF) and solid farmyard manure from cattle (FYM) in two consecutive years in silage maize grown on a sandy soil. Maize yields responded positively to each of these N sources applied at rates up to 150 kg of mineral fertilizer equivalents per ha per year (i.e. NFRV × total N rate). The observed NFRVs, relative to calcium ammonium nitrate fertilizer, amounted to 78% for MC, 82% for PS, 79% for CS, 56% for SF and 34% for FYM when averaged over both years. NFRVs were positively related to the ammonium‐N share in the total N content. Rye cover crop establishment after the harvest of maize reduced nitrate concentrations of the upper groundwater by, on average, 7.5 mg nitrate‐N/L in the first year and 10.9 mg/L in the second year, relative to a bare soil. Regardless of the presence of a cover crop, nitrate concentrations responded positively to the applied rate of effective N (total N × NFRV) but less to postharvest residual soil mineral N.     

Effects of Slow‐Release Fertilizers on Tomato Growth and Nitrogen Leaching

Tomatoes (Lycopersicon esculentum Mill.) were grown in 9.46‐L plastic pots in a glasshouse for evaluation of their growth and nitrogen (N) losses through leaching. Plants were fertilized with either ammonium nitrate (AN) or one of three slow‐release N fertilizers. The slow‐release N fertilizers were Georgia Pacific liquid 30‐0‐0 (L30), Georgia Pacific granular 42‐0‐0 (N42), and Georgia Pacific granular 24‐0‐0 (N24). Each fertilizer was applied at 112 low N rate (L) and 224 high N rate (H) kg N ha^?1. The pots were filled with either a sandy soil from Florida or a loam soil from Georgia. Increasing the N rate did not influence shoot biomass at 19 days after transplanting (DAT) and increased biomass production at 77 DAT. Shoot biomass differed significantly among fertilizer treatments. The accumulation of N in shoots was significantly influenced by fertilizer source, rate, and soil type. The plants grown in the loam soil accumulated significantly more N than those grown in the sandy soil with the same treatment. In the loam soil, the highest and lowest N accumulations occurred in the N42‐H and N24‐L treatments, respectively; and in the sandy soil the corresponding treatments were AN‐H and N24‐L. The amount of N leached varied with the different fertilizers, soils, and time. The net leaching of N ranged from ?0.4% to 6.3% of the fertilizer N applied for the loam soil and 6.5% to 32.9% for the sand soil. The net amount of N leached from the loam soil at both high and low application rates declined in the following order: AN > N24 > N42 > L30; the corresponding order for the sandy soil was AN‐H > N42‐H > L30‐H > N24‐H. L30 had the least leaching potential, and ammonium nitrate had the most. Slow‐release fertilizers had significantly less leaching N than did ammonia nitrate.     

Residual effect and nitrate leaching in grass‐arable rotations: effect of grassland proportion,sward type and fertilizer history

A key point in designing grass‐arable rotations is to find the right balance between the number of cultivations and the length of the grass phase. In a field experiment, we investigated the effect of cropping history (grazed unfertilized grass–clover and fertilized [300 kg N per hectare] ryegrass, proportion of grassland and previous fertilizer use) on crop growth and nitrate leaching for 2 years following grassland cultivation. In the final year, the effect of perennial ryegrass as a catch crop was investigated. The nitrogen fertilizer replacement value (NFRV) of grassland cultivation was higher at 132 kg N per hectare in the rotation with 75% grassland compared with on average 111 kg N per hectare in rotations with 25 and 38% grassland and the NFRV of ryegrass in the rotation was higher than that of grass–clover. Nitrate leaching following cultivation was not affected by the proportion of grassland in the crop rotation or sward type. However, there was a considerable effect of having a ryegrass catch crop following the final barley crop as nitrate leaching was reduced from 60 to 9 kg N per hectare. When summarizing results from the crop rotations over a longer period (1997–2005), management strategy adopted in both the grassland and arable phases appeared to be the primary instrument in avoiding nutrient losses from mixed crop rotations, irrespective of grass proportion. In the arable phase, the huge potential of catch crops has been demonstrated, but it is also important to realize that all parts of the grass‐arable crop rotations must be considered potentially leaky.     

The effect of grassland renovation on soil mineral nitrogen and on nitrate leaching during winter

Renovation of grassland may increase the mineralization of organic material and leads to a high amount of mineral N in soil which can be leached in the winter period. Soil mineral N (SMN) in autumn and calculated nitrate leaching during winter were measured after the renewal of 8 y–old cut grassland on a sandy soil in NW Germany in 1999 to 2002. Several factors, which may influence the intensity of N mineralization, were investigated in the 2 years following renewal: the season of renovation (spring or late summer/early autumn), the technique (rotary cultivator or direct drilling), and the amount of N fertilization (0 or 320 kg N ha^–1 y^–1 in the 7 years before the renovation). Calculated nitrate‐N leaching losses during winter were significantly higher following renewal in early autumn (36–64 kg N ha^–1) compared to renewal in spring (1–7 kg N ha^–1). This effect was only significant in the first, not in the second winter after renovation. The renovation technique had a significant effect on the nitrate‐N leaching losses only in the first year after the renovation. Direct drilling led to higher leaching losses (35 kg N ha^–1) than the use of a rotary cultivator (30 kg N ha^–1) in the same year. Calculated nitrate losses (on average over 60 kg N ha^–1) were highest after renewal of N‐fertilized grassland in late summer/early autumn. To minimize N leaching losses, it would be more effective to plan grassland renewal in spring rather than in late summer/autumn. Another, however, less effective option is to reduce N fertilization before a renovation in autumn.     

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.     

Leaching of nitrate and phosphorus after autumn and spring application of separated solid animal manures to winter wheat

Animal slurry can be separated into solid and liquid manure fractions to facilitate the transport of nutrients from livestock farms. In Denmark, untreated slurry is normally applied in spring whereas the solid fraction may be applied in autumn, causing increased risk of nitrate and phosphorus (P) leaching. We studied the leaching of nitrate and P in lysimeters with winter wheat crops (Triticum aestivum L.) after autumn incorporation versus spring surface application of solid manure fractions, and we compared also spring applications of mineral N fertilizer and pig slurry. Leaching was compared on a loamy sand and a sandy loam soil. The leaching experiment lasted for 2 yr, and the whole experiment was replicated twice. Nitrate leaching was generally low (19–34 kg N/ha) after spring applications of mineral fertilizer and manures. Nitrate leaching increased significantly after autumn application of the solid manures, and the extra nitrate leached was equivalent to 23–35% of total manure N and corresponded to the ammonium content of the manures. After spring application of solid manures and pig slurry, only a slight rise in N leaching was observed during the following autumn/winter (<5% of total manure N). Total P leaching was 40–165 g P/ha/yr, and the application of solid manure in autumn did not increase P leaching. The nitrogen fertilizer replacement value of solid manure N was similar after autumn and spring application (17–32% of total N). We conclude that from an environmental perspective, solid manure fractions should not be applied to winter wheat on sandy and sandy loam soils under humid North European conditions.     

The effect of crop, N-level, soil type and drainage on nitrate leaching from Danish soil

Abstract. Nitrate leaching measurements in Denmark were analysed to examine the effects of husbandry factors. The data comprised weekly measurements of drainage and nitrate concentration from pipe drains in six fields from 1971 to 1991, and weekly measurements of nitrate concentration in soil water, extracted by suction cups at a depth of 1 m, from 16 fields in 1988 to 1993. The soils varied from coarse sand to sandy clay loam.
The model used for analysing the data was: Y = exp (1.136–0.0628 clay + 0.00565N + crop ) D^0.416, with R²= 0.54, where Y is the nitrate leaching (kg N/ha per y), clay is the % clay in 0-25 cm depth (%), N is the average N-application in the rotation (kg/ha/y) and D is drainage (mm/y). The most important factor influencing leaching was the crop type. Grass and barley undersown with grass showed low rates of leaching (17-24 kg/ha/y). Winter cereal following a grass crop, beets, winter cereals following cereals and an autumn sown catch crop following cereals showed medium rates of leaching (36-46 kg/ha/y). High rates of leaching were estimated from winter cereals following rape/peas, bare soil following cereals and from autumn applications of animal manure on bare soil (71-78 kg/ha/y). Estimates of leaching from soil of 5, 12 and 20% clay were 68, 44 and 26 kg/ha/y, respectively. Leaching was estimated to rise significantly with increasing amounts of applied N.
The model is suitable for general calculations of the effects of crop rotation, soil type and N-application on nitrate leaching from sandy soil to sandy clay loarns in a temperate coastal climate.     

Leaching of spring—applied fertilizer nitrogen: measurement and simulation

Abstract. The leaching of spring-applied fertilizer nitrogen was measured by soil sampling on three soils widely used for spring cropping: a loamy sand, a sandy loam and a sandy silt loam. Soils were fallow during the experiment. Results were compared with simulations obtained with a computer leaching model. The model differentiated well between soil types, and predicted mineral nitrogen remaining in the top 30, 60 or 90 cm with reasonable precision. It tended to over-estimate the rate of nitrification of ammonium from ammonium nitrate fertilizers. The causes of occasional large discrepancies between sampling and measurement are discussed.     

Leaching and Recovering of Nitrogen Following N Fertilizers Application to the Soil in a Laboratory Study

Following soil fertilization, nitrogen (N) is partially lost. The objective of this study was to evaluate leaching and recovery of N after addition of fertilizers to the soil. Two experiments were conducted in leaching columns submitted to frequent water percolations. In the leaching experiment, urea, ammonium nitrate, and six coated N fertilizers were utilized; in the N recovery experiment, treatments consisted of urea, potassium nitrate, ammonium sulfate, and ammonium nitrate, combined or not with percolation. Percolations were performed weekly with quantification of ammonium and nitrate in the percolated. The recovered N was obtained by summing total N percolated with N in the soil. Nitrate leaching was highest from amide-N fertilizers, with no differences between them showing that coating urea was not efficient to decrease N leaching. Nitric fertilizers had the lowest recovery of N, probably due to the occurrence of denitrification caused by the frequent water percolation.     

An empirical model for estimating nitrate leaching as affected by crop type and the long-term N fertilizer rate

Abstract. An empirical model was developed for prediction of annual average nitrate leaching as affected by the long-term rate of N fertilization and crop type. The effect of N fertilization was estimated from annual values of nitrate leaching obtained from two Danish investigations of drainage from pipe drains with four rates of N fertilization on a loamy sand and sandy clay loam from 1973-89. The effect of crop at normal N fertilization was estimated from 147 observations of annual nitrate leaching obtained from field measurements. The nitrate leaching model consists of a relative N fertilization submodel and an absolute submodel for specific combinations of crop, soil and drainage at the normal rate of N fertilization. The relative submodel is Y/Y _lN= exp[0.7l(N/ N₁– I)], where Y is the nitrate leaching (kg N/ha per year) at fertilization rate N , and Y _IN and N₁ are the corresponding values at the normal rate of N fertilization. The relative submodel is valid for cereals, root crops and grass leys fertilized with mineral fertilizer at N/N ₁ < 1.5, and on the prerequisite that the fertilization rate N has been constant for some years. To illustrate the use of the relative leaching submodel, estimated values of Y _IN corrected to mean annual drainage for 1970 to 1990 in Denmark for spring cereals and grass on sandy and loamy soils are given as input to the relative leaching submodel. The model can be used for sandy to loamy soils to estimate the mean nitrate leaching over a number of years.     

Mineral fertilizers with iron influence spring rape,maize and soil properties

ABSTRACT

Because of low content of available iron (Fe) in soils and its poor mobility in plants, iron fertilization is necessary. Different forms of iron (mineral salts, chelates, nanomaterials) and fertilization strategies (soil and foliar application of solid or liquid fertilizers) are used. The effect of solid mineral fertilizers (A: a mixture of ammonium nitrate and dolomite; B: a mixture of ammonium nitrate and sulfate) enriched with iron sulfate was assessed during a three-year pot experiment. Iron addition did not change the yield of spring rape (first year) or maize (second and third year) significantly, and the effect on iron content in the plants was ambiguous. Fertilizer B with iron had the greatest yield-forming effect, increasing the yield of aboveground parts by 355–874%, and of roots by 211–692% in particular years. All fertilizers (especially containing sulfur) acidified the soil. After the experiment, pH of the soil fertilized with sulfur was 4.1, and of the unfertilized soil – 5.2. Iron addition increased the content of mobile and exchangeable iron in the soil by 12–110% and 2–58%, respectively, but not the content of the fraction bound to MnO_x. Combination of sulfur and iron fertilization has a potential to improve soil abundance and plant yield.     

Nitrous oxide fluxes from grassland in the Netherlands: II. Effects of soil type, nitrogen fertilizer application and grazing

Intensively managed grasslands are potentially a large source of nitrous oxide (N₂O) in the Netherlands because of the large nitrogen (N) input and the fairly wet soil conditions. To quantify the effects of soil type, N-fertilizer application and grazing on total N₂O losses from grassland, fluxes of N₂O were measured weekly from unfertilized and mown, N fertilized and mown, and N fertilized and predominantly grazed grassland on a sand soil, a clay soil, and two peat soils during the growing season of 1992. Total N₂O losses from unfertilized grassland were 2.5–13.5 times more from the peat soils than from the sand and clay soils. Application of calcium ammonium nitrate fertilizer significantly increased N₂O flux on all sites, especially when the soil was wet. The percentage of fertilizer N applied lost to the atmosphere as N₂O during the season ranged from 0.5 on the sand soil to 3.9 on one of the peat soils. Total N₂O losses were 1.5–2.5 times more from grazed grassland than from mown grassland, probably because of the extra N input from urine and dung. From 1.0 to 7.7% of the calculated total amount of N excreted in urine and dung was emitted as N₂O on grazed grassland. The large N₂O losses measured from the peat soils, combined with the large proportion of grassland on peat in the Netherlands, mean that these grasslands contribute significantly to the total emission from the country.     

Plant availability and leaching of 15N-labelled mineral fertilizer residues retained in agricultural soil for 25 years: A lysimeter study

Background

A high use-efficiency of fertilizer N remains essential to sustain high crop productivity with low environmental impact. However, little is known on the long-term lability of mineral fertilizer N.

Aims

To quantify crop uptake and leaching of ¹⁵N-labelled mineral fertilizer that has been retained in an agricultural soil for 25–30 years in crops with variable growing season.

Methods

A field plot received ¹⁵N-labelled mineral fertilizers over a period of 5 years and was then kept under arable cropping for 12 years. After relocation to 16 lysimeters, the topsoil grew set-aside grassland for the next 13 years. Then crop uptakes and leaching losses of ¹⁵N remaining in soil was tested over a 2-year period by either converting set-aside grass to production grassland, or by replacing it with spring barley (+/− autumn cover crop) or vegetation-free fallow. All treatments received unlabelled mineral N fertilizers.

Results

Crop uptake and leaching of ¹⁵N were generally highest in the first test year after termination of the set-aside. The leaching of residual ¹⁵N in soil declined in the order: vegetation-free soil (4.7%), spring barley (1.9%), spring barley + cover crop (0.7%) and production grassland (0.2%). Corresponding losses for the second leaching period were 2.7%, 0.9%, 0.4% and 0.06%. There was a fixed relationship between leaching losses of ¹⁵N and total N.

Conclusions

After residing in soil for 25–30 years, the lability of labelled mineral N fertilizer residues appeared slightly higher than the lability of bulk soil N. Autumn vegetation was crucial for reducing leaching losses.     

Influence of <Superscript>15</Superscript>N-labeled ammonium sulfate and straw on nitrogen retention and supply in different fertility soils

Microbial immobilization/mineralization and mineral fixation/release of ammonium are important for N retention and supply. However, the rates of such processes vary among different fertility soils and fertilization management practices. Three long-term different fertilized soils were used to simulate a range in soil fertility level and incubated with different N amendments for 144 days. The dynamics of ¹⁵N derived from ammonium sulfate (AS) or straw in different soil N pools and the ammonium sulfate-N or straw-N retention and supply were studied. In the absence of straw, the amount of ammonium sulfate-N present as fixed ammonium was 1.1–3.5-fold higher than that present as soil microbial biomass N (SMBN), although ammonium sulfate-derived SMBN and its mineralization increased by increasing soil fertility level. Straw addition significantly (P < 0.05) enhanced the relative importance of the SMBN pool on ammonium sulfate-N retention and supply compared with the fixed ammonium-N pool, and the former exceeded the latter in higher fertility soils. Regardless of soil fertility levels, straw addition significantly blocked the release of ammonium sulfate-N from the fixed ammonium-N pool. The SMBN pool was more important in straw-N retention and supply than the fixed ammonium-N pool, confirming that straw-N cycling depended more on biotic processes. The percentage of mineralized ammonium sulfate-N or straw-N from SMBN was higher than that released from fixed ammonium, indicating the higher availability of SMBN. Generally, the mineral fixation/release of ammonium was the main process for mineral fertilizer N retention and supply in the low fertility soil with or without straw addition, whereas microbial immobilization/mineralization became the main process in the high fertility soil with straw addition. Our results gave insights on the ammonium sulfate-N or straw-N retention and supply in different fertility soils, providing suggestions for optimizing straw management and synchronizing N supply with crop demand.     

How important is plant litter to the regulation of mineral‐N leaching to streams in winter? An observations‐led experimental approach

Ammonium‐N concentrations were frequently observed to exceed nitrate‐N concentrations in an intermittently flowing stream draining acid grassland in North Yorkshire. This prompted the design of a soil microcosm experiment to investigate the role of litter in the leaching of ammonium and nitrate from soil profiles during winter. Drainage water was analysed weekly for N species, pH, mineral acid anions and dissolved organic carbon (DOC) for a period of 11 weeks, while extractable mineral‐N was determined after 5 and 11 weeks. The results demonstrate that litter plays an important role in reducing mineral‐N leaching in winter months. They also suggest that DOC from the litter participates in mineral‐N retention in the soil profiles in winter. Ammonium‐N and nitrate‐N concentrations measured in the microcosm drainage water are similar to those of the stream.     

Imaging‐optode measurements of ammonium distribution in soil after different manure amendments

The choice of manure application technique can affect both the spatial distribution of ammonium in soil and net nitrogen (N) mineralization, and thereby N availability to crops. In this study we compared net N mineralization and spatial ammonium distribution after different degrees of incorporation of solid chicken manure and cattle slurry into soil. Ammonium‐specific fluorescing optodes were assembled with manure applied to soil in closed chambers and the spatial distribution of ammonium in different treatments was measured for 2 weeks. The results indicated that much ammonium from the manures was quickly adsorbed to clay particles. Consequently, the ammonium concentration in the soil solution was threefold higher in the sandy soil than in the clay soil studied. Ammonium was distributed over a larger soil volume from manure applied below the soil surface than from manure applied above. Because the optodes excluded ammonium adsorbed to soil particles, net N mineralization was instead studied in separate incubations using extraction with potassium chloride solution for determination of ammonium and nitrate. When manure was kept concentrated in lumps rather than being mixed with soil, nitrate levels were about five times smaller after 1 week and 5–10% more of the manure N occurred as mineral N after 2 weeks. There were no differences in net N mineralization between surface application and subsurface incorporation. In this study a new technique to visualize and measure ammonium patterns around manure in soil proved to be useful for evaluating ammonium distribution and adsorption, but net N mineralization required incubations.     

Use of long-term monitoring data to derive a relationship between nitrogen surplus and nitrate leaching for grassland and arable land on well-drained sandy soils in the Netherlands

The decrease in nitrogen (N) use in agriculture led to improvement of upper groundwater quality in the Sand region of the Netherlands in the 1991–2009 period. However, still half of the farms exceeded the European nitrate standard for groundwater of 50 mg/l in the 2008–2011 period. To assure that farms will comply with the quality standard, an empirical model is used to derive environmentally sound N use standards for sandy soils for different crops and soil drainage conditions. Key parameters in this model are the nitrate-N leaching fractions (NLFs) for arable land and grassland on deep, well-drained sandy soils. NLFs quantify the fraction of the N surplus on the soil balance that leaches from the root zone to groundwater and this fraction represents N available for leaching and denitrification. The aim of this study was to develop a method for calculating these NLFs by using data from a random sample of commercial arable farms and dairy farms that were monitored in the 1991–2009 period. Only mean data per farm were available, which blocked a direct derivation of NLFs for unique combinations of crop type, soil type and natural soil drainage conditions. Results showed that N surplus leached almost completely from the root zone of arable land on the most vulnerable soils, that is, deep, well-drained sandy soils (95% confidence interval of NLF 0.80–0.99), while for grassland only half of the N surplus leached from the root zone of grassland (0.39–0.49). The NLF for grassland decreased with 0.015 units/year, which is postulated to be due to a decreased grazing and increased year-round housing of dairy cows. NLFs are positively correlated with precipitation surplus (0.05 units/100 mm for dairy farms and 0.10 units/100 mm for arable farms). Therefore, an increase in precipitation due to climate change may lead to an increase in leaching of nitrate.     

间歇淋洗干湿交替条件下氮肥的氮行为研究

采用土柱淋洗试验方法 ,对包膜尿素、尿素和硝酸铵在石碴土和粘壤质石灰性土壤中氮的行为进行了评价。结果表明 ,包膜尿素、尿素和硝酸铵的回收总氮量 (包括淋洗溶液中各种形态氮 ,土壤吸附的肥料氮和残余的肥料氮 )分别为施入总氮量的 90.5%、74.2 %、93.5%和91.5%、58.5%、91.1%。在 1750mL淋洗溶液中NO3--N分别占淋洗溶液中总氮量的 90%以上。在 7次淋洗干湿交替之后 ,土壤吸附的肥料氮 (NH4+-N和NO3--N)均不超过施氮总量的2.1% ;包膜尿素有62.7%和70.8%的氮以颗粒肥料存在于土壤中。 3种氮肥中包膜尿素较尿素和硝酸铵在土壤中释放持续的时间显著延长 ,尿素的氨挥发损失较高 ,硝酸铵淋失较快     

几种新型氮肥对叶菜硝酸盐累积和土壤硝态氮淋洗的影响

应用土柱模拟试验的方法,研究了在高肥力菜田土壤条件下,施用几种新型氮肥对两茬叶菜硝酸盐积累和土壤硝态氮淋洗的影响。结果表明,在高肥力菜田土壤上,施用几种新型氮肥都未能明显提高第一茬油菜的生物量,硫硝铵（A SN）却降低了生物量,而第二茬菠菜不施肥处理生物量下降。尿素＋硝化抑制剂DM PP（En tec46）、尿素＋硝化抑制剂DCD（U＋DCD）和有机无机复混肥（OIF）3种氮肥显著降低了油菜硝酸盐含量。尿素＋玉米秸秆（U＋M S）和硫硝铵＋硝化抑制剂DM PP（En tec26）减少了土壤NO3^--N的向下淋洗,而尿素＋保水剂（U＋SAP）增加土壤NO3^--N的向下淋洗。