中国南方大棚蔬菜地氮平衡与损失

High rates of fertilizer nitrogen (N) are applied in greenhouse vegetable fields in southeastern China to maximize production;however,the N budgets of such intensive vegetable production remain to be explored.The goal of this study was to determine the annual N balance and loss in a greenhouse vegetable system of annual rotation of tomato,cucumber,and celery at five N (urea) application rates (0,348,522,696,and 870 kg N ha-1 year-1).Total N input to the 0-50 cm soil layer ranged from 531 to 1 053 kg ha-1,and N fertilizer was the main N source,accounting for 66%-83% of the total annual N input.In comparison,irrigation water,wet deposition,and seeds in total accounted for less than 1% of the total N input.The fertilizer N use efficiency was only 18% under the conventional application rate of 870 kg N ha-1 and decreased as the application rate increased from 522 to 870 kg N ha-1.Apparent N losses were 196-201 kg N ha-1,of which 71%-86% was lost by leaching at the application rates of 522-870 kg N ha-1.Thus,leaching was the primary N loss pathway at high N application rates and the amount of N leached was proportional to the N applied during the cucumber season.Moreover,dissolved organic N accounted for 10% of the leached N,whereas NH3 volatilization only contributed 0.1%-0.6% of the apparent N losses under the five N application rates in this greenhouse vegetable system.     

氮肥用量对太湖水稻田间氨挥发和氮素利用率的影响

Ammonia volatilization losses, nitrogen utilization efficiency, and rice yields in response to urea application to a rice field were investigated in Wangzhuang Town, Changshu City, Jiangsu Province, China. The N fertilizer treatments, applied in triplicate, were 0 （control）, 100, 200, 300, or 350 kg N ha^-1. After urea was applied to the surface water, a continuous airflow enclosure method was used to measure ammonia volatilization in the paddy field. Total N losses through ammonia volatilization generally increased with the N application rate, and the two higher N application rates （300 and 350 kg N ha^-1） showed a higher ratio of N lost through ammonia volatilization to applied N. Total ammonia loss by ammonia volatilization during the entire rice growth stage ranged from 9.0% to 16.7% of the applied N. Increasing the application rate generally decreased the ratio of N in the seed to N in the plant. For all N treatments, the nitrogen fertilizer utilization efficiency ranged from 30.9% to 45.9%. Surplus N with the highest N rate resulted in lodging of rice plants, a decreased rate of nitrogen fertilizer utilization, and reduced rice yields. Calculated from this experiment, the most economical N fertilizer application rate was 227 kg ha^-1 for the type of paddy soil in the Taihu Lake region. However, recommending an appropriate N fertilizer application rate such that the plant growth is enhanced and ammonia loss is reduced could improve the N utilization efficiency of rice.     

氮肥用量及其分施比例对棉花氮利用和土壤氮平衡的影响

The Yellow River valley is one of the three largest cotton production areas in China.An experiment was performed in cotton fields of Anyang,China from 2013 to 2014 to investigate the effects of nitrogen(N) application rate and the ratio between basal and topdressing N fertilizer on N balance in a soil-plant system,N use efficiency,and cotton yield.Five N application rates as treatments were applied with the same split application ratio.Half of the N(50% basal fertilizer) was applied at pre-planting and the other half(50% topdressing fertilizer) at the initial flowering stage.These treatments were:zero N(N0,control),90 kg N ha~(-1)(N90(5/5)),180 kg N ha~(-1)(N180(5/5)),270 kg N ha~(-1)(N270(5/5),a reduced N rate),and 360 kg N ha~(-1)(N360(5/5),a conventional N rate).Additional 2 split application ratios as treatments were applied with the same N rate of 270 kg N ha~(-1).The split application ratios between basal N and topdressing N were 30%:70%(N270(3/7)) and 70%:30%(N270(7/3)).Results demonstrated that soil NH_4-N content in the 0–60 cm layer and NO3-N content in the 0–20 cm layer increased with increased N rate at the squaring and boll-opening stages and then decreased to lower levels at the initial flowering and harvest stages.Soil NO_3-N content in the 20–60 cm layer after the initial flowering stage increased with the increase of topdressing N rate.Soil apparent N surplus varied at different growth stages,while the soil apparent N surplus over the entire growth period exhibited a positive relationship at N rates over 180 kg ha~(-1).Seed cotton yield of N270(3/7) was the highest of all treatments.Plant N uptake,N agronomic efficiency,and apparent N recovery efficiency of N270(3/7) were significantly higher than those of N270(5/5) and N270(7/3) in both growing seasons.These suggest both economic and ecological benefits in cotton production in the Yellow River valley could be created,by appropriately reducing total N application rate and increasing the ratio of topdressing to basal N fertilizer at the initial flowering stage.     

不同的水稻品种产量及生理氮素利用效率的差异

Efficient use of N in agricultural practice can increase yield, decrease production costs and reduce the risk of environmental pollution. Effects of N fertilizer application rates on grain yield and physiological N use efficiency (PE) in relation to the accumulation and redistribution of biomass and N in rice (Oryza sativa L.) cultivars were studied at two experimental farms of Nanjing Agricultural University, Nanjing, China in 2004. Three high N use efficiency (NUE) rice cultivars (Wuyunjing 7, Nanguang and 4007) and one low NUE rice cultivar (Elio) with similar growth patterns were studied under seven N rates (0, 60, 120, 180, 240, 300 and 360 kg ha^-1). Grain yield increased with the N application rate and attained plateau at 180 kg N ha^-1 for rice cultivars at each site. Increasing N rate decreased PE for biomass and grain yield. Grain yield and PE of Elio were about 20% and 18% lower than those of high NUE cultivars. Differences in biomass, N accumulation and N redistribution were observed at the post-heading stage among rice cultivars with differing NUEs. The less reproductive tillers of Elio resulted in less demand for C and N during grain filling, thus leading to lower PE of Elio compared with the high NUE rice cultivars.     

中国太湖地区稻麦轮作农田硝态氮动态与氮素平衡

Nitrate-nitrogen (NO 3--N) dynamics and nitrogen (N) budgets in rice (Oryza sativa L.)-wheat (Triticum aestivum L.) rotations in the Taihu Lake region of China were studied to compare the effects of N fertilizer management over a two-year period. The experiment included four N rates for rice and wheat, respectively: N1 (125 and 94 kg N ha-1 ), N2 (225 and 169 kg N ha-1 ), N3 (325 and 244 kg N ha-1 ), and N0 (0 kg N ha-1 ). The results showed that an overlying water layer during the rice growing seasons contributed to moderate concentrations of NO 3--N in sampled waters and the concentrations of NO 3--N only showed a rising trend during the field drying stage. The NO 3--N concentrations in leachates during the wheat seasons were much higher than those during the rice seasons, particularly in the wheat seedling stage. In the wheat seedling stage, the NO 3--N concentrations of leachates were significantly higher in N treatments than in N0 treatment and increased with increasing N rates. As the NO 3--N content (below 2 mg N L-1 ) at a depth of 80 cm during the rice-wheat rotations did not respond to the applied N rates, the high levels of NO 3--N in the groundwater of paddy fields might not be directly related to NO 3--N leaching. Crop growth trends were closely related to variations of NO 3--N in leachates. A reduction in N application rate, especially in the earlier stages of crop growth, and synchronization of the peak of N uptake by the crop with N fertilizer application are key measures to reduce N loss. Above-ground biomass for rice and wheat increased significantly with increasing N rate, but there was no significant difference between N2 and N3. Increasing N rates to the levels greater than N2 not only decreased N use efficiency, but also significantly increased N loss. After two cycles of rice-wheat rotations, the apparent N losses of N1, N2 and N3 amounted to 234, 366 and 579 kg N ha-1 , respectively. With an increase of N rate from N0 to N3, the percentage of N uptake in total N inputs decreased from 63.9% to 46.9%. The apparent N losses during the rice seasons were higher than those during the wheat seasons and were related to precipitation; therefore, the application of fertilizer should take into account climate conditions and avoid application before heavy rainfall.     

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.     

施用控释肥提高直播水稻氮的利用率

Field trials on a silt-loamy paddy soil derived from shallow-sea deposit in direct seeding rice fields were conducted in Zhejing ,China,in 1996 to compare N efficiency of controlled release fertilizers (LP fertilizers) with the conventional urea.Six treatments including CK (no N fertilizer),conventional urea and different types of LP fertilizers at different rates were designed for two succeeding crops of early and late rice.A blend of different types of LP fertilizers as a single preplant “co-situs“ application released n in a rate and amount synchronizing with uptake pattern of direct seeding rice.A single preplant application of the LP fertilizers could meet the N requirement of rice for the whole growth period without need of topdressing,Using LP fertilizer blends ,equivalent grain yields could be maintained even if the N fertilization rates were reduced by 25%-50% compared with the conventional urea .Agronomi efficiency of the LP fertilizers was 13.6%-86.4% higher than that of the conventional urea in early rice and 100%-164.1% in late rice,depending on the amounts of the LP fertilizers applied.N fertilizer recovery rate incereased from 27.4% for the conventional application of urea to 41.7%-54.1%,for the single preplant “co-situs“ application of the LP fertilizers,Use of the LP fertilizers was promising if the increse in production costs due to the hihg LP fertilizer prices could be compensated by increase in yield and N efficiency,reduction in labor costs and improvement in environment.     

保护地蔬菜轮作体系中两种不同复合肥对产量的影响及其氮素动态特征

Yield and N uptake of tomato (Lycopersicum esculentum Mill.) and pepper (Capsicum annuum L.) crops in five successive rotations receiving two compound fertilizers (12-12-17 and 21-8-11 N-P₂O₅-K₂O) were studied to determine 1) crop responses, 2) dynamics of NO₃-N and NH₄-N in different soil layers, 3) N balance and 4) system-level N efficiencies. Five treatments (2 fertilizers, 2 fertilizer rates and a control), each with three replicates, were arranged in the study. The higher N fertilizer rate, 300 kg N ha^-1 (versus 150 kg N ha^-1), returned higher vegetable fruit yields and total aboveground N uptake with the largest crop responses occurring for the low-N fertilizer (12-12-17) applied at 300 kg N ha^-1 rather than with the high-N fertilizer (21-8-11). Ammonium-N in the top 90 cm of the soil profile declined during the experiment, while nitrate-N remained at a similar level throughout the experiment with the lower rate of fertilizer N. At the higher rate of N fertilizer there was a continuous NO₃-N accumulation of over 800 kg N ha^-1. About 200 kg N ha^-1 was applied with irrigation to each crop using NO₃-contaminated groundwater. In general, about 50% of the total N input was recovered from all treatments. Pepper, relative to tomato, used N more efficiently with smaller N losses, but the crops utilized less than 29% of the fertilizer N over the two and a half-year period. Local agricultural practices maintained high residual soil nutrient status. Thus, optimization of irrigation is required to minimize nitrate leaching and maximize crop N recovery.     

太湖地区稻麦轮作下氮素径流和淋洗损失

Although nitrogen （N） loss through runoff and leaching from croplands is suspected to contribute to the deterioration of surrounding water systems, there is no conclusive evidence for paddy soils to prove this hypothesis. In this study, field plot experiments were conducted to investigate N losses through runoff and leaching for two consecutive years with 3 N fertilization rates in rice （Oryza sativa L.）-wheat （Triticum aestivum L.） rotations in the Taihu Lake region, China. A water collection system was designed to collect runoff and leachates for both the rice and wheat seasons. Results showed that dissolved N （DN）, rather than particulate N （PN）, was the main form of N loss by runoff. The NO3^--N concentration in runoff was between 0.1 and 43.7 mg L^-1, whereas the NH4^＋-N concentration ranged from below detection limit to 8.5 mg L^-1. Total N （TN） loads by runoff were 1.0-17.9 and 5.2-38.6 kg ha^-1 during rice and wheat seasons, respectively, and the main loss occurred at the early growing stage of the crops. Nitrogen concentrations in leachates during the rice seasons were below 1.0 mg L^-1 and independent of the N application rate, whereas those during the wheat season increased to 8.2 mg L^-1 and were affected by the fertilizer rate. Annual losses of TN through runoff and leaching were 13.7-48.1 kg ha^-1 from the rice-wheat cropping system, accounting for 5.6%-8.3% of the total applied N. It was concluded that reduction in the N fertilization rate, especially when the crop was small in biomass, could lower the N pollution potential for water systems.     

施氮水平对水稻氮肥利用率和径流负荷的影响

氮肥的过量施用导致显著的氮素损失,降低了环境质量。减少氮肥投入使其与作物需求相匹配对于保持农业生产的可持续发展具有至关重要的作用。为了评估不同施氮水平对水稻生产过程中的氮肥利用率和径流负荷的影响,利用长期实验基地开展了相关研究,实验共设置了4个施氮水平,即0、100、200和300 kg/hm~2。结果显示,随着施氮量的增加,粮食产量显著提高,而农学效率和偏肥生产力却呈相反趋势。作物地上部氮肥回收率则呈先增加后减少的趋势,并在200 kg/hm~2时达到峰值;氮素径流损失随施氮量的增加而增加。     

两个氮素利用率不同的水稻品种根系形态及生理特性的差异

The variation in nitrogen (N) uptake by rice has been widely studied but differences in rice root morphology that may contribute to this variation are not completely understood. Field and greenhouse experiments were carried out to study N accumulation, root dry weights, total root lengths, root surface areas, and root bleeding rates of two rice cultivars, Elio with low N-use efficiency and Nanguang with high N-use efficiency. Low (1 mmol N L^-1) and high (5 mmol N L^-1) N applications were established in the greenhouse experiment, and the N rates were 0, 120, and 240 kg ha^-1 in the field experiments at Jiangning and Jiangpu farms, Nanjing, China. The results showed that the N accumulation, root dry weight, total root length, and root surface area increased with an increase in N application. At the heading stage, N accumulation in the shoots and roots of Nanguang was greater than that of Elio in the field experiments and that of Elio at 5 mmol N L^-1 in the greenhouse experiment. After the heading stage, N accumulation was higher for Nanguang at both 1 and 5 mmol N L^-1 in the greenhouse experiment. The total root length and root surface area were significantly different between the two cultivars. Over the range of the fertilizer application rates, the root lengths of Nanguang at Jiangning Farm were 49%-61% greater at booting and 26%-39% greater at heading than those of Elio, and at Jiangpu Farm they were 22%-42% and 26%-38% greater, respectively. Nanguang had a greater root bleeding rate than Elio. It was concluded that the N-use efficiency of the two rice cultivars studied depended to a great extent on the root morphological parameters and root physiological characteristics at different growth stages.     

不同施氮量下北方稻田一次与分次施氮对水稻产量的影响

设计了适量和过量总施氮量下的一次和分次施氮的田间试验,研究了不同施肥方式对山西半干旱地区肥力水平较低的盐渍型水稻土水稻产量的影响。结果表明,适宜氮量(N198kghm-2)下,水稻插秧前基肥一次性施氮较分三次在不同生育期施氮稻谷平均增产达10%;但过量施氮下,一次性基肥施氮较分三次施用平均减产6.6%。总施氮量小于适宜施氮量时,基肥一次性施氮较分三次施用平均增产则达到30%。插秧前基肥一次性施氮与基肥和分蘖初期分两次施氮相比,稻谷产量无明显差异。这说明插秧前和分蘖初期是该地水稻的有效施肥期。在不施磷肥或磷肥做基肥一次施用而氮肥分次施用的情况下,基肥氮磷施用比例也影响所施用氮肥的肥效;因此,就所试验的肥力较低的盐渍型水稻土来说,可以实行在减量施氮下的插秧前基肥一次性施氮,而不需要追施氮肥,并且在施P2O5130kghm-2的条件下,总施氮190kghm-2即可满足高产,因而可以减少习惯施氮量的1/3。     

施肥深度和用量对华南果园土壤氮磷流失的影响

Fertilizers are heavily applied in orchards of the hilly and mountainous topography of South China and may increase nutrient loadings to receiving waters. A simple runoff collecting system was used to measure the effects of different fertilization treatments on total N and P concentrations of surface runoff in a Chinese chestnut （Castanea mollissima Blume） orchard in Dongyuan County, Guangdong Province, China. In such orchards, fertilizer was typically applied in two short furrows or pits on either side of each tree. Treatments included three application depths （surface, 10 cm and 20 cm）, and three application rates （low, median and high）. Results showed that 90.5% of the runoff water samples had a total N concentration higher than 0.35 mg·L^-1 and 54.2% had a total P concentration higher than 0.1 mg·L^-1. Fertilizer application at all depths and at all but the lowest rate significantly increased total N and P concentrations in runoff water. Fertilization with chemical compound fertilizer at a soil depth of 20 cm produced significantly lower （P 〈 0.05） total N concentration in runoff than both surface and 10-cm depth fertilization, and significantly lower （P 〈 0.05） total P concentration in runoff than surface fertilization. Total N and P concentrations in runoff significantly increased with the application rate of organic fertilizers. With the exception of total P concentrations, which were not significantly different between the control and fertilization at a rate of 119 kg P ha-1 in organic form, all the other fertilization treatments produced significantly higher total N and total P concentrations in runoff than the control. A fertilization depth ≥ 20 cm and an application rate ≤ 72 kg N ha-1 or 119 kg P ha^-1 for compound organic fertilizer was suggested to substantially reduce N and P runoff losses from hillslope orchards and to protect receiving waters in South China.     

不同施氮水平对春玉米氮素利用及土壤硝态氮残留的影响

过量施用氮肥造成的环境问题日益严重,氮肥合理使用成为了人们研究的热点。通过研究不同施氮水平对春玉米氮素利用及土壤硝态氮残留的影响,为氮肥的合理利用提供依据。通过在北京市通州区农业技术推广站进行田间小区试验,研究了不同施氮量（0、50、100、200和300kg·hm^-2）对春玉米产量及氮素利用效率、氮平衡和土壤硝态氮累积量的影响。结果表明：（1）春玉米在施氮量为200kg·hm^-2时达到最高产量,为9006．4kg．hm^-2,不同氮肥水平的氮肥利用率在19．7％-25．8％之间,在100kg·hm^-2时的利用效率最高,达到25．8％。（2）作物吸氮量随输入量的增加而增加,氮盈余主要以土壤残留为主,表观损失在氮盈余中的比例虽小,但随施氮量的增加而增加的趋势更加明显。（3）硝态氮在180cm土层中的累积量随氮素输入量的增加而显著增加,在300kg·hm^-2时达到最高值,为195kg·hm^-2,在施氮水平为100kg·hm^-2时作物生长的需要就基本上能够得到满足,而在高施氮水平下（200和300kg·hm^-2）时土壤中的硝态氮出现富集现象,对环境形成一定的威胁。