太湖地区水稻追肥的氨挥发损失和氮素平衡

采用密闭室通气法和¹⁵N 微区试验, 对太湖地区水稻不同生育期追施氮肥的氨挥发损失、水稻对氮肥的吸收利用和土壤氮素残留情况进行了研究。结果表明, 氨挥发损失主要发生在施肥后1 周内, 峰值出现在施肥后1~2 d, 氨挥发速率变化与田面水NH₄⁺-N 浓度变化规律一致, 分蘖肥和穗肥氨挥发损失率分别为16.7%和6.3%; 水稻分蘖肥的作物氮素利用率低于穗肥, 分别为36.7%和49.6%, 主要原因是穗肥的氨挥发损失较少,并且更易于向籽粒转移; 2 次追施氮肥的表观损失率分别为52.8%和40.7%; 在土壤中残留肥料氮为10.6%, 大都集中在0~20 cm 土壤中, 耕层以下较少。本结果表明, 在水稻孕穗时期施氮肥有利于提高氮肥利用效率、减少氮肥损失, 主要体现在穗肥拥有较低的氨挥发损失率和较高的籽粒利用率。     

Organic Fertilizer Source and Application Method Impact Ammonia Volatilization

ABSTRACT

Ammonia (NH₃) volatilization from fertilizer applications reduces efficiency and poses environmental hazards. This study used semi-open static chambers to measure NH₃ volatilization from organic fertilizers (feather meal, blood meal, fish emulsion, cyano-fertilizer) to evaluate the impacts of fertilizer source, application method, and rate on NH₃ volatilization. In 2014, two application rates (28 and 56 kg N ha^?1) were applied to lettuce (Lactuca sativa L.). Solid fertilizers (feather meal, blood meal) were preplant applied in a subsurface band, whereas liquid fertilizers (fish emulsion, cyano-fertilizer) were applied weekly through drip irrigation beginning two weeks after transplanting. In 2015, a single application rate (28 kg N ha^?1) was applied to cucumber (Cucumis sativus L.). Solid fertilizers were applied in either subsurface or surface bands. There was a significant difference in NH₃ volatilization among fertilizers, but there was little difference between application rates. Liquid fertilizers had lower NH₃ emissions than solid fertilizers due to their timing and placement. In 2014, blood meal at 56 kg N ha^?1 and feather meal at both rates had the highest NH₃ fluxes. In 2015, surface-banded blood and feather meal had the highest NH₃ fluxes. Fertilizer decisions for organic systems should consider NH₃ emission losses and practices for their reduction.     

Nitrogen Volatilization from Arizona Irrigation Waters

A laboratory study was initiated to investigate the effects of temperature (25, 30, 35, and 40 °C) and water quality on the loss of fertilizer nitrogen (N) through volatilization out of irrigation waters collected from 10 different Arizona sources. A 300‐mL volume of each water source was placed in 450‐mL beakers open to the atmosphere in a constant‐temperature water bath with 10 mg of analytical‐grade ammonium sulfate [(NH₄)₂SO₄] dissolved into each sample. Small aliquots were drawn at specific time intervals over a 24‐h period and then analyzed for ammonium (NH₄ ⁺)‐N and nitrate (NO₃ ^?)‐N concentrations. Results showed potential losses from volatilization to be highly temperature dependent. Total losses (after 24 h) ranged from 30–48% at 25 °C to more than 90% at 40 °C. Volatilization loss of fertilizer N from irrigation waters was found to be significant and should be considered when making decisions regarding fertilizer N applications for crop production in Arizona particularly when using ammonia‐based fertilizers.     

Effects of fertilizer type and rate on summer maize grain yield and ammonia volatilization loss in northern China

Purpose

In this study, we analyzed the effects of different maize varieties with nitrogen utilization efficiency, fertilizer type, and rate on the ammonia volatilization emission of farmland. Aimed to seek the best matching method to improve grain yield and fertilizer utilization efficiency of summer maize simultaneously.

Materials and methods

In field experiments, we choose two maize varieties with different nitrogen utilization efficiency (Zhengdan958, Z and Lainong14, L) as material. Set four different fertilizer treatments (200 kg N hm^?2 inorganic fertilizer (U1), 100 kg N hm^?2 inorganic fertilizer (U2), 200 kg N hm^?2 organic fertilizer (M1), and 100 kg N hm^?2 organic fertilizer (M2) to study their effect on NH₃ emission and loss, maize grain yield, and nitrogen accumulation.

Results and discussion

Ammonia volatilization accounted for 8.61–21.68% of applied N. Under the same variety, ammonia volatilization accumulation after fertilization was as follows: U1 > U2 > M1 > M2. Ammonia volatilization rates increased first and then gradually decreased after the fertilization. The ammonia volatilization loss and cumulative loss increased due to increased nitrogen fertilizer application rate. The average nitrogen accumulation and harvest index of 200 kg N hm^?2 N treatments were higher than 100 kg N hm^?2 N treatments, and the difference between the inorganic fertilizer and organic fertilizer was not significant. In 2016 and 2017, the average yield of Zhengdan958 was 11,758.79 kg hm^?2, which was 15.78% higher than that of Lainong14, and the difference between the two fertilizer types was not significant. The average yield of 200 kg N hm^?2 N treatment was 11,959.42 kg hm^?2, which was 20.13% higher than those of 100 kg N hm^?2 N treatment.

Conclusions

By changing the type of fertilizer, replacing chemical fertilizers with organic fertilizer can reduce the loss of ammonia volatilization and promote the synergistic improvement to yield and resource utilization efficiency. Among them, using nitrogen-efficient varieties and using organic fertilizer instead of chemical fertilizer was beneficial to reduce the loss of ammonia volatilization, increase the accumulation of nitrogen, and promote the growth of maize to obtain high yield.

     

添加脲酶抑制剂NBPT对麦秆还田稻田氨挥发的影响

氨挥发是稻田氮素损失的重要途径,为探明脲酶抑制剂NBPT对小麦秸秆还田稻田中氨挥发的影响,采用密闭室通气法,在太湖地区乌珊土上,研究了脲酶抑制剂n-丁基硫代磷酰三胺(NBPT)对小麦秸秆还田稻田中施肥后尿素水解和氨挥发动态变化的影响。结果表明:稻田氨挥发损失主要集中在基肥和分蘖肥时期。添加NBPT可明显延缓尿素水解,推迟田面水NH4+-N峰值出现的时间,并降低NH4+-N峰值,降低了田面水氨挥发速率和挥发量。NBPT的效果在基肥和分蘖肥施用后尤为明显,不加NBPT时施入的尿素在2~3 d内基本水解彻底,NH4+-N和氨挥发速率在第2 d即达到峰值,两次施肥后NH4+-N峰值分别为132.3 mg·L-1和66.3mg·L-1,氨挥发峰值为15.6 kg·hm-2·d-1和10.4 kg·hm-2·d-1;而添加NBPT后,NH4+-N峰值推迟至施肥后第4 d出现,NH4+-N峰值降至70.7 mg·L-1和51.6 mg·L-1,氨挥发峰值降至4.7 kg·hm-2·d-1和2.6 kg·hm-2·d-1。添加NBPT使稻田氨挥发损失总量从73.3 kg(N)·hm-2(占施氮量的24.4%)降低至34.5 kg(N)·hm-2(占施氮量的11.5%),降低53%。在添加小麦秸秆稻田中添加NBPT通过延缓尿素水解而显著降低了氨挥发损失。     

华北平原氮肥周年深施对冬小麦-夏玉米轮作体系土壤氨挥发的影响

氮肥深施能有效减少土壤氨挥发，然而目前国内外关于小麦-玉米轮作体系氮肥深施缺乏周年系统性研究。本试验于2018年10月—2019年10月在中国科学院栾城农业生态系统试验站小麦-玉米轮作农田进行，利用动态箱法研究不同深施模式氨挥发损失率、氨挥发特征，旨在探讨冬小麦-夏玉米轮作体系下土壤氨排放对氮肥深施的响应，为减少农业源氨排放和优化农田施肥提供理论依据。试验设置5个处理：不施肥（CK）、常规肥料表施（T₁）、缓释肥表施（T₂）、缓释肥基追肥分层深施（T₃）、缓释肥一次性分层深施（T₄）。结果表明：氨挥发主要发生在玉米追肥季，占全年氨挥发量的84.84%；T₁、T₂、T₃和T₄处理的周年氨挥发累积量分别为22.75 kg·hm^-2、6.17 kg·hm^-2、2.25 kg·hm^-2和0.55 kg·hm^-2，分别占总施肥量的4.86%、1.32%、0.48%和0.13%。与常规肥料表施（T₁）相比，缓释肥处理（T₂、T₃和T₄）分别降低72.88%、90.11%和97.32%的氨挥发损失；一次性深施处理（T₄）能避开土壤氨高挥发期，周年氨挥发累积量与不施肥处理（0.43 kg·hm^-2）没有显著差异，且显著低于表施处理。CK、T₁、T₂、T₃和T₄全年产量分别为8.31 t·hm^-2、13.20 t·hm^-2、12.66 t·hm^-2、14.42 t·hm^-2和14.22 t·hm^-2；与常规肥料表施（T₁）相比，缓释肥深施（T₃和T₄）均可提高作物产量，分别增产9.25%和7.75%。而缓释肥表施（T₂）产量略有降低。综合考虑土壤氨排放和作物产量，缓释肥表施（T₂）可以显著降低土壤氨挥发，但是作物产量不稳定；而氮肥深施（T₃、T₄）能在保证作物高产的基础上显著降低土壤氨排放，是一种高效、简便、环境友好的施肥方式。     

Stability of stored N-(n-butyl) thiophosphoric triamide (NBPT) treated urea-based fertilizers

ABSTRACT

The effectiveness of N-(n-butyl) thiophosphoric triamide (NBPT) in reducing ammonia volatilization from urea-based fertilizers has been thoroughly investigated. However, the stability of this inhibitor during storage of NBPT treated urea and urea ammonium nitrate (UAN) needs further investigation. We compared ammonia volatilization from NBPT treated urea (360 mg NBPT kg^?1 urea) and UAN (180 mg NBPT L^?1 UAN) that were stored at room temperature for 6, 3 and 0 months. We measured ammonia volatilization with cylindrical chambers fitted with acid-charged discs at five times for 21 d. Total ammonia volatilization (measured as a % of applied nitrogen) was significantly greater in untreated urea and UAN (32% to 33%) than those in NBPT treated urea and UAN (6% to 12%). Reduction of ammonia volatilization was not significantly different among NBPT treated urea (73% to 81%) and UAN (63% to 73%) irrespective of storage time. This implies that farmers can mix their urea-based fertilizers with NBPT formulation 6 months prior to fertilization without compromising the ammonia volatilization reducing property of the NBPT.     

Nutrient dynamics,dehydrogenase activity,and response of the rice plant to fertilization sources in an acid lateritic soil

Abstract

Rice variety IR 36, grown under flooding, was studied in 1998 to determine the effects of fly ash, organic, and inorganic fertilizers on changes in pH and organic carbon, release of nutrients (NH₄ ⁺-N, Bray's P, and NH₄OAc K), and dehydrogenase activity in an acid lateritic soil at 15-day intervals. Application of fly ash at 10?t?ha^?1 alone did not improve the availability of NH₄ ⁺-N, or P, as well as the rice grain yield. Availability of NH₄ ⁺-N (35.3–36.9?mg?kg^?1), and P (12.3–14.6?mg?kg^?1) at 15 days after transplanting, and rice grain yields (48.0–51.7?g per pot) were similar under the various fertilization sources such as inorganic fertilizer alone, inorganic fertilizer?+?fly ash or inorganic fertilizer?+?green manure?+?fly ash. Mean dehydrogenase activity was the highest (8.47?µg triphenyl formazon g^?1 24?h^?1) under the mixed fertilization treatments with green manure. At the end of the cropping season (75 days after transplanting), pH, organic carbon, and dehydrogenase activity were higher under the mixed fertilization treatments involving green manure by 3, 15 and 154%, respectively, compared with the inorganic fertilizer alone.     

Laboratory Evaluation on Ammonia Volatilization from Coated Urea Fertilizers

Coated urea fertilizers are assumed to enhance crop yield and reducing the environmental pollution. Nevertheless, many of the coated urea fertilizers are expensive, thus not readily available for most farmers. In addition, many of these fertilizers release N not in tandem with the plant’s need, thus retard growth. Therefore, a laboratory study was conducted to evaluate effects of coated urea fertilizers on N losses via volatilization. Measurement of ammonia volatilization was carried out using the closed-dynamic air flow system. The study for ammonia volatilization was conducted using different rates of fertilizer (50, 100, and 200 kg N ha^?1) with different types of fertilizer (Urea, Sulfur-coated urea; SCU and Gypsum sulfur coated urea using rotating drum; GSCUD) in 37 days of incubation. The results indicate that SCU represents the best fertilizer which decreases the amount of ammonia volatilization at each rate of fertilizer. Besides, the rate of 50 kg N ha^?1 has the lowest percentage of ammonia volatilization. Moreover, the result proved the effectiveness of coating urea fertilizer may reduce the ammonia loss to the environment and new product which GSCUD can be comparable to the commercial product.     

Effects of Temperature and Soil Type on Ammonia Volatilization from Slow-Release Nitrogen Fertilizers

Ammonia (NH₃) volatilization is the major pathway for mineral nitrogen (N) loss from N sources applied to soils. The information on NH₃ volatilization from slow-release N fertilizers is limited. Ammonia volatilization, over a 78-d period, from four slow-release N fertilizers with different proportions of urea and urea polymer [Nitamin 30L (liquid) (L30), Nitamin RUAG 521G30 (liquid) (G30), Nitamin 42G (granular) (N42), and Nitroform (granular) (NF)] applied to a sandy loamy soil was evaluated. An increase in temperature from 20 to 30 °C increased cumulative NH₃ volatilization loss in the sandy soil by 1.4-, 1.7-, and 1.8-fold for N42, L30, and G30, respectively. Increasing the proportion of urea in the slow-release fertilizer increased NH₃ volatilization loss. At 30 °C, the cumulative NH₃ volatilization over 78 d from a sandy soil accounted for 45.6%, 43.9%, 22.4%, and <1% of total N applied as N42, L30, G30, and NF, respectively. The corresponding losses in a loamy soil were 9.2%, 3.1%, and 1.7%. There was a significantly positive correlation between NH₃ volatilization rate and concentration of NH₄-N released from all fertilizers, except for NF (n = 132; r = 0.359, P = 0.017 for N42; r = 0.410, P = 0.006 for L30; and r = 0.377, P < 0.012 for G30). Lower cumulative NH₃ volatilization from a loamy soil as compared to that from a sandy soil appeared to be related to rapid nitrification of NH₄-N in the former soil than that in the latter soil. These results indicate the composition of slow-release fertilizer, soil temperature, and soil type are main factors to dominate NH₃ volatilization from slow- release fertilizers.     

有机肥无机肥配施对稻田氨挥发和水稻产量的影响

在南方红壤区双季稻田进行田间试验,研究等氮、磷、钾量条件下,有机无机肥配施对稻田氨挥发及水稻产量的影响。结果表明,有机无机肥配合施用能显著地降低稻田氨挥发,减少氮素损失,提高氮肥利用率。单施化肥(尿素),其氨挥发损失达37.8%,而单施有机肥和有机无机肥各半配合施用,氨挥发损失分别为0.7％-1.0％和7.2％-18.2％。田间氨挥发持续的时间,早稻约在施肥后20d,晚稻为9-10d。虽然有机无机肥各半配合施用的水稻产量与单施化肥的相近,均比对照提高约70％,但前者的氮损失少,其氮肥利用率为34.9％,高于化肥处理(33.2％)和有机肥处理(28.0%)。有机无机肥配合施用对提高水稻产量和降低氮肥环境负效应的综合效应最佳。     

水氮调控对设施土壤氨挥发特征的影响

基于连续6年设施番茄水氮调控定位试验,采用高分辨激光光谱法观测分析灌水下限(土壤水吸力为W_1:25 kPa、W_2:35 kPa、W_3:45 kPa)和施氮量(N_1:75 kg N/hm~2、N_2:300 kg N/hm~2、N_3:525 kg N/hm~2)对设施土壤氨挥发通量、累积挥发量、番茄产量及单产累积排放量的影响。结果表明:灌水下限、施氮量及两者交互作用极显著的影响设施土壤氨挥发通量峰值、累积挥发量、单产氨挥发累积量、氨挥发损失率和番茄产量。氨挥发通量表现为施氮后6～8天氨挥发达到峰值。经验S模型可以较好地表征基肥和追肥2个时期氨挥发累积量随时间的变化,氨挥发特征参数表现为基肥期以灌水下限和水氮交互影响为主,追肥期以施氮量和水氮交互影响为主。与基肥相比,采用滴灌追肥可显著的降低氨挥发累积量94.78%～96.30%。受土壤pH和土壤NH_4~+-N含量及施肥带比例影响,氨挥发的氮损失率在0～2%。施氮量为300 kg N/hm~2和灌水下限25 kPa组合的水氮处理(W_1N_2)是协调氨挥发量和设施番茄产量的最佳水氮管理模式。     

Structural Characteristics and Oxygen Consumption of the Epipelic Biofilm in Three Lowland Streams Exposed to Different Land Uses

Ammonia (NH₃) emission from nitrogen (N) fertilizers used in agriculture decreases N uptake by the crop and negatively impacts air quality. In order to better understand the factors influencing NH₃ emission from agriculture, this research was conducted with four major soils used for potato production: Biscayne Marl Soil (BMS, pH 7.27), and Krome Gravelly Loam (KGL, pH 7.69) from Florida; and Quincy Fine Sand (QFS, pH 6.65), and Warden Silt Loam (WSL, pH 6.46) from Washington. Potassium nitrate (KNO₃), ammonium nitrate (NH₄NO₃), ammonium sulfate ((NH₄)₂SO₄) or urea ((NH)₂CO) sources were evaluated for ammonia volatilization at 75 kg N ha^?1 rate. The soil water regime was maintained at either 20 or 80% of field capacity (FC), and incubated at 11, 20 or 29°C. Results indicated that NH₃ volatilization rate at 20% FC was 2 to 3-fold greater than that at 80% FC. The cumulative volatilization loss over 28 days ranged from 0.21% of N applied as NH₄NO₃ to 25.7% as (NH₄)₂SO₄. Results of this study demonstrate that NH₃ volatilization was accelerated at the low soil water regime. Moisture quotient (Q) is defined as a ratio of NH₃ emission rate at 20% FC to that at 80% FC both at the same temperature. The peak Q values of NH₃ volatilization were up to 20.8 for the BMS soil at 20°C, 112.9 for the KGL soil at 29°C, 19.0 for the QFS soil at 20°C, and 74.1 for the WSL soil at 29°C, respectively. Thus, maintaining a suitable soil water regime is important to minimize N-loss via NH₃ volatilization and to improve N uptake efficiency and air quality.     

Reactions of urea phosphate in calcareous and alkaline soils: I. Ammonia volatilization

Abstract

Nitrogen (N) loss in the form of volatilized ammonia (NH₃) is a considerable problem when ammonium (NH₄ ⁺⁾ forming fertilizers are applied to calcareous or alkaline soils. The volatilization of NH₃ from urea phosphate (UP) and urea (U) was studied on three selected soils (Hayhook SL, Laveen L, and Latene L) with the use of a laboratory aeration system. Urea phosphate and U were each applied at rates of 0, 50, 100, and 200 mg N kg^‐1 soil, either to the surface dry or in solution or mixed with the soil. The volatilized NH₃ was trapped in sulfuric acid, sampled periodically, and analyzed for N with the semi microkjeldahl distillation apparatus.

The highest N loss in the form of NH₃ occurred when U was applied to Hayhook soil (neutral to acidic, coarse textured, and low CaCO₃ content). However, UP applied to Hayhook soil resulted in the lowest NH₃‐N loss. Less NH₃‐N loss was found from U application to Laveen and Latene soils (fine textured with higher CaCO₃ content) than with Hayhook soil. The general trend was higher N loss when a surface application was made, either dry or in solution, than when the fertilizer was mixed with the soil. This trend showed an increase in the amount of volatilized NH₃ with increasing N application rates.

Generally, UP is a potential fertilizer for supplying N and phosphorus (P) as plant nutrients with a low potential for losses due to NH₃ volatilization.     

Calcium chloride and ammonium thiosulfate as ammonia volatilization inhibitors for urea fertilizers

Abstract

Surface‐applied urea fertilizers are susceptible to hydrolysis and loss of nitrogen (N) through ammonium (NH₃) volatilization when conditions favorable for these processes exist. Calcium chloride (CaCl₂) and ammonium thiosulfate (ATS) may inhibit urease activity and reduce NH₃ volatilization when mixed with urea fertilizers. The objective of this study was to evaluate the effectiveness of CaCl₂ and ATS as urea‐N loss inhibitors for contrasting soil types and varying environmental conditions. The proposed inhibitors were evaluated in the laboratory using a closed, dynamic air flow system to directly measure NH₃ volatilization. The initial effects of CaCl₂ on ammonia volatilization were more accentuated on an acid Lufkin fine sandy loam than a calcareous Ships clay, but during volatilization periods of ≥ 192 h, cumulative N loss was reduced more on the Ships soil than the Lufkin soil. Calcium chloride delayed the commencement of NH₃ volatilization following fertilizer application and reduced the maximum N loss rate. Ammonium thiosulfate was more effective on the Lufkin soil than the Ships soil. For the Lufkin soil, ATS reduced cumulative urea‐N loss by 11% after a volatilization period of 192 h. A 20% (v/v) addition of ATS to urea ammonium nitrate (UAN) was most effective on the coarse textured Lufkin soil whereas a 5% addition was more effective on the fine textured, Ships soil. Rapid soil drying following fertilizer application substantially reduced NH₃ volatilization from both soils and also increased the effectiveness of CaCl₂ but not ATS. Calcium chloride and ATS may function as limited NH₃ volatilization inhibitors, but their effectiveness is dependent on soil properties and environmental conditions.     

Estimation of Ammonia Volatilization from a Paddy Field after Application of Controlled-Release Urea Based on the Modified Jayaweera–Mikkelsen Model Combined with the Sherlock–Goh Model

The continuous airflow enclosures with an acid trap method was widely used to investigate ammonia (NH₃) volatilization in field; however, it could be time-consuming for the estimation of NH₃ volatilization in field with the application of controlled-release urea (CRU) because NH₃ volatilization with CRU application could occur during the entire crop growth period. An NH₃ volatilization estimation method based on the modified Jayaweera–Mikkelsen (J-M) model combined with the Sherlock–Goh model was used to simulate NH₃ volatilization in a paddy field after 255 kg N ha^?1 as CRU (polymer-coated urea with the concentration of 43% nitrogen, 100% for basal) and urea (70% for basal, 30% for topdressing) during the rice growth period including flooded and non-flooded periods in Wuxi, China. Results indicated that NH₃ volatilization can be modeled with the proposed measure because no significant difference (P< 0.001) was observed between the simulated values and the observed values; the correlation coefficient (r²) was 0.615 for CRU and 0.840 for urea during the flooded period, and 0.991 for CRU and 0.946 for urea during the non-flooded period. Compared with urea, NH₃ volatilization was minimized by 43.2% with the application of CRU based on simulated value within the rice growth period, which was 40.40 kg N ha^?1 for CRU and 78.62 kg N ha^?1 for urea during the flooded period, and 5.52 kg N ha^?1 for CRU and 2.33 kg N ha^?1 for urea during the non-flooded period. Therefore, CRU could be a promising nitrogen fertilizer to prevent NH₃ losses in the rice paddies at the investigated area.     

Injury of leatherleaf fern and tomato from volatilized ammonia after fertilizer application

Abstract

A commercially blended 7–2–11 fertilizer containing 27 g ? kg^‐1 soluble ammoniacal nitrogen (NH₄‐N) was evaluated for ammonia (NH₃) volatilization and injury to leatherleaf fern (Rumohra adiantiformis) and an indicator plant, tomato (Lycopersicon esculentum). Closed system laboratory incubation studies on pH‐buffered sand medium indicated a very highly significant response (p≤0.001) of NH₃ volatilization to sand pH. The greatest risk from NH₃ emissions at pH 8.6 and 32°C appeared to be in the 5 to 70 hour period after fertilizer application. Gypsum (CaSO₄) did not affect NH₃ volatilization. Ammonium nitrate (NH₄NO₃) was identified as the main source of NH₃ volatilization from this fertilizer formulation, while on an equal mass basis, ammonium sulphate [(NH₄)₂SO₄] was more important. Both tomato and immature leatherleaf fern fronds were highly sensitive to volatilized NH₃ from the fertilizer. A critical phytotoxic NH₃(aq) concentration in sand solution of 0.14 mM was estimated for immature fern fronds. Mature fern fronds were significantly more tolerant of NH₃ emissions, which may explain their observed resistance to NH₃ injury in the field. Assessment of selected soil and irrigation water pH's from a leatherleaf fern growing area in Florida indicated a strong likelihood that volatilized NH₃ injury to foliage can occur under field conditions.     

不同深施方式对太湖地区稻田氨挥发和氮肥利用率的影响

本研究以太湖地区稻田为研究对象开展连续两年的田间试验，通过设置不施氮肥（CK）、常规施氮（CN）、减氮表施（RN）、减氮侧深施（RNS）和减氮穴施（RNP）5种施氮处理，探究不同深施方式对稻田氨挥发与氮肥利用率的影响。结果表明，与表施处理（CN和RN）相比，RNS和RNP通过降低田面水NH₄⁺-N浓度和pH分别减少30.95%~41.54%和66.71%~72.23%的氨挥发排放（P<0.05）。相较于RN处理，RNP促进水稻根系生长并增加根区土壤有效氮含量，进而增加水稻产量（6.23%），提高氮肥利用率（50.15%），降低土壤氮盈余（63.92%）（P<0.05）。与CN处理相比，RNS显著降低土壤氮盈余（29.20%）（P<0.05），但水稻吸氮量和氮肥利用率均未显著增加。相较于RNS，RNP进一步降低氨挥发损失（50.84%）和土壤氮盈余（51.07%），提高氮肥利用率（40.40%）（P<0.05）。综上所述，RNP的农学和环境效益最高，但因穴施机械及肥料造粒技术等因素的限制，尚难应用于实际生产；而侧深施肥在我国水稻大规模集约化生产中效益较高且切实可行。     

华北山前平原农田生态系统氮通量与调控

针对华北太行山前平原冬小麦-夏玉米轮作农田, 研究农田常规施肥[400 kg(N)·hm^-2·a^-1]条件下作物氮素吸收与损失通量过程, 并根据各氮素输出通量特征开展管理调控。研究结果表明, 全年小麦-玉米轮作农田系统氮输入总量为561~580 kg(N)·hm^-2, 输出量468~494 kg(N)·hm^-2, 两季作物总盈余86~93 kg(N)·hm^-2, 其中有机氮为24~36 kg·hm^-2。氨挥发和NO₃^--N 淋溶损失是该区域农田氮素损失的主要途径, 是氮肥利用率低的重要原因。平均每年因氨挥发而造成的肥料氮损失量为60 kg(N)·hm^-2, NO₃^--N 淋溶损失量为47~84kg(N)·hm^-2, 两者占施肥总量的30%。每年因硝化-反硝化过程造成的肥料损失很小, 仅为5.0~8.7 kg(N)·hm^-2。通过施肥后适时灌水、合理调控灌水时间与用量, 以及利用秸秆还田与肥料混合施用等管理措施可改善氮素的迁移和转化规律, 有效减少氨挥发和NO₃^--N 淋溶损失, 并结合缓/控释肥与精准施肥技术, 充分利用土壤本身矿质氮素, 可有效提高养分利用效率和作物产量, 改善农田生态环境与促进农业持续和谐发展。     

Effects of cotton (Gossypium hirsutum L.) straw and its biochar application on NH3 volatilization and N use efficiency in a drip-irrigated cotton field

Reducing ammonia (NH₃) volatilization is a practical way to increase nitrogen (N) fertilizer use efficiency (NUE). In this field study, soil was amended once with either cotton (Gossypium hirsutum L.) straw (6 t ha^?1) or its biochar (3.7 t ha^?1) unfertilized (0 kg N ha^?1) or fertilized (450 kg N ha^?1), and then soil inorganic N concentration and distribution, NH₃ volatilization, cotton yield and NUE were measured during the next two growing seasons. In unfertilized plots, NH₃ volatilization losses in the straw-amended and biochar-amended treatments were 38–40% and 42–46%, respectively, less than that in control (i.e., unamended soil) during the two growing seasons. In the fertilized plots, NH₃ volatilization losses in the straw-amended and biochar-amended treatments were 30–39% and 43–54%, respectively, less than that in the control. Straw amendment increased inorganic N concentrations, cotton yield, cotton N uptake and NUE during the first cropping season after application, but not during the second. In contrast, biochar increased cotton N uptake and NUE during both the first and the second cropping seasons after application. Furthermore, the effects of biochar on cotton N uptake and NUE were greater in the second year than in the first year. These results indicate that cotton straw and cotton straw biochar can both reduce NH₃ volatilization and also increase cotton yield, N uptake and NUE. In addition, the positive effects of one application of cotton straw biochar were more long-lasting than those of cotton straw.