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1.
华北山前平原典型厚包气带硝态氮分布累积规律 总被引：5，自引：1，他引：4
包气带是连接大气层和含水层水分和养分转换的纽带,也是农田NO_3~–-N分布和累积的重要场所和向含水层淋失的通道,因此研究包气带土壤中NO_3~–-N的分布累积规律对防止地下水NO_3~–-N污染至关重要。本文以中国科学院栾城试验站典型的厚包气带为对象,在无施肥处理(N0)和施氮肥600 kg/(hm~2·a)(N600)两种处理的多年试验田中,利用Geoprobe获取0~10.5 m深度土壤样品,研究厚包气带NO_3~–-N垂向分布、累积规律,并分析其影响因素。结果表明:N0中NO_3~–-N基本保持不变,长年施氮肥600 kg/(hm~2·a)使得NO_3~–-N淋溶至10.5 m,并在深层包气带中形成累积,累积的峰值由土壤的质地和含水量决定;NO_3~–-N的分布和累积主要受水分运移、土壤质地和反硝化作用影响。 相似文献
2.
A. Elmi A. Madani R. Gordon P. MacDonald G. W. Stratton 《Water, air, and soil pollution》2005,160(1-4):119-132
Nitrate-N (NO3 ?-N) is a ubiquitous pollutant in both surface and groundwater in many agro-ecosystems. This has elicited a concerted effort to identify management strategies that mitigate NO3 ?–N pollution, without compromising crop yield. This study was conducted on a field site located at the Bio-Environmental Engineering Centre (BEEC) in Truro, NS, Canada during 1999 and 2000. The site has been used since 1997 to investigate the relative effect of inorganic versus organic fertilizer (liquid hog manure; LHM) applied at rates (70 kg N ha?1) on NO3 ?-N leaching from a carrot rotation system. NO3 ?-N concentrations were monitored in both the soil profile and in tile drainage effluents from eight treatment plots. The LHM treatment elicited significantly (P < 0.01) higher soil NO3 ?-N concentrations than inorganic fertilizer (IF) in June and October during 1999, but not 2000. The sampling date and soil depth were significant in most cases. Annual flow weighted averages (FWA) of NO3 ?-N in drainage water were generally greater for plots receiving LHM (15.4 and 10.5 mg L?1 for 1999 and 2000, respectively), when compared to IF (8.9 and 6.0 mg L?1 for 1999 and 2000, respectively), but the difference was significant (P < 0.05) only in 1999. Maximum NO3 ?-N concentrations in drainage water were similar for both treatments, while the LHM treatment had a significantly higher percentage of samples that were > 10 mg L?1. The total NO3 ?-N load was greater for the LHM treatment when compared to the IF treatment in 1999. Barley and carrot yields were unaffected by treatment applications. 相似文献
3.
4.
为解决区域土壤质地类型针对性氮肥施用问题,在轻壤土和黏壤土上分别设置不施氮肥,氮肥基追比3∶7,4∶6,5∶5,6∶4和7∶3处理,研究小麦产量、水氮利用效率以及土壤含水量、贮水量、NH_4~+-N、NO_3~--N动态变化规律。结果表明:轻壤质土壤氮肥基追比4∶6的处理小麦产量、水分利用效率、氮肥生产效率最高分别为8 265.3 kg/hm~2,27.6 kg/(hm~2·mm),34.4 kg/kg。黏壤质土壤氮肥基追比5∶5的处理小麦产量、水分利用效率、氮肥生产效率最高分别为8 363.2 kg/hm~2,28.3 kg/(hm~2·mm),34.8 kg/kg。小麦不同生育期各土层含水量垂直分布变化较大,轻壤质土壤含水量在9.3%～26.2%,而黏壤质为9.7%～27.6%;小麦全生育期内土壤贮水量呈先升高后降低趋势,黏壤质土壤贮水量高于轻壤质。氮素追施量越多土壤表层NH_4~+-N与NO_3~--N含量越高,且随土层加深土壤NH_4~+-N与NO_3~--N含量降低,受降水影响轻壤质土壤NH_4~+-N与NO_3~--N更易于向土层深处淋溶,成熟期黏壤质各土层的NH_4~+-N和NO_3~--N含量均多于轻壤质。说明黏壤质土壤保水保氮肥能力强于轻壤质,氮肥基追比可以适当增加。 相似文献
5.
华北山前平原农田土壤硝态氮淋失与调控研究 总被引：11，自引：5，他引：6
本文依托中国科学院栾城农业生态系统试验站小麦-玉米一年两熟长期定位试验, 应用土钻取土和土壤溶液取样器取水的方法, 研究了不同农田管理措施下土壤硝态氮的累积变化, 计算了不同氮肥处理通过根系吸收层的硝态氮淋失通量。结果表明, 小麦-玉米生长季土壤硝态氮累积量和淋失量随着施氮量的增加显著增加, 相同氮肥水平下增施磷、钾肥增加了作物的收获氮量, 施磷肥增加的作物收获氮量最高可达123kg·hm-2·a-1, 施钾肥增加的作物收获氮量最高为31 kg·hm-2·a-1。不同灌溉水平下0~400 cm 土体累积硝态氮随着灌溉量的增加而降低, 控制灌溉(小麦季不灌水, 玉米季灌溉1 水)、非充分灌溉(小麦季灌溉2~3 水, 玉米季按需灌溉)、充分灌溉(小麦季灌溉4~5 水, 玉米季按需灌溉)各处理剖面累积硝态氮量分别为1 698 kg·hm-2、1148 kg·hm-2 和961 kg·hm-2。与非充分灌溉和充分灌溉处理相比, 控制灌溉在100~200 cm 土层硝态氮累积量显著高于其他层次, 2003~2005 年间控制灌溉剖面增加的硝态氮量占施肥总量的23%; 非充分灌溉处理剖面增加的硝态氮量占施肥总量的22%; 充分灌溉处理剖面增加的硝态氮量占施肥总量的47%。免耕措施降低了作物产量, 影响土壤水的运移, 增加了硝态氮的淋失风险。根据作物所需降低氮素投入(N 200 kg·hm-2·a-1), 增施磷、钾肥, 控制灌溉量是减少华北山前平原地区硝态氮淋失, 保护地下水的有效措施。 相似文献
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不同肥料结构对红壤稻田氮素迁移的影响 总被引：14，自引：3，他引：14
不同肥料结构对红壤稻田淹水层、不同深度渗漏水、外排水和土壤剖面中氮素的含量、形态及其动态变化的影响研究结果表明 ,各处理淹水层、外排水和渗漏水中NH4+-N含量明显高于NO3--N。淹水层中N的含量 ,水稻生育前期以单施化肥的高 ,约相当于配施有机肥的 1.18～ 1.20倍 ,而水稻生育后期 ,后者为前者的 1.11～ 1.2 1倍。各处理外排水中N素的输出量均以苗期最高 ,单施化肥明显大于配施有机肥。土壤剖面中NH4+-N向下迁移比碱解N更为明显 ,且配施有机肥的远高于单施化肥的 ,而NO3--N则相反。不同深度渗漏水中NO3--N的比例 ,上层 (30cm)低于下层 (50cm) ,随水逸出的N量各处理渗漏水均小于外排水 ;随水输入的N量远低于随水输出的N量 ,且以单施化肥的N亏损最大。水稻未利用的N量也以单施化肥的最大 ,约为配施有机肥的 1.0 9倍。 相似文献
7.
本试验利用渗滤池设施，采用化学分析和同位素技术相结合的方法研究了北京地区潮土表层中施用氮肥后ＮＯ３＾－－Ｎ转化积累及其１３０ｃｍ土体的淋洗状况。常规分析结果表明，在春小麦和夏玉米的生育前期可以观察到氮素明显地向ＮＯ３＾－－Ｎ的转化积累，其强度随尿素施用量的增加而明显增加，而尿素、硝铵、硫铵等不同氮肥品种处理之间有差异但大多不显著。同时夏玉米期间转化积累作用比春小麦期间强烈。＾１５Ｎ标记试验结果表明 相似文献
8.
不同灌溉施肥方式下尿素态氮在土壤中迁移转化特性的研究 总被引：29，自引：3，他引：29
采用室内土柱模拟试验方法 ,研究了不同灌溉施肥方式下尿素态氮在土壤中的迁移、淋溶和转化特征。结果表明 ,灌水量及水肥供应方式是决定尿素态氮在土壤中迁移、转化和淋失的关键因素。氮素淋溶量随灌水量的增加而增加 ;与浇灌施肥相比 ,滴灌施肥显著地降低了氮素的淋溶损失。在淋失的氮素形态中 ,以尿素态氮为主 ,其次为硝态氮 ,铵态氮的淋失量最低。灌水量低时 ,滴灌施肥铵态氮在土壤上层明显累积 ;灌水量增加后 ,这种累积作用减弱。灌水量低时 ,灌溉施肥的土壤硝态氮变化呈上低下高 ,增加灌水量降低了土壤中硝态氮含量 ;滴灌施肥显著地减少了尿素态氮的淋溶损失 ,增加了土壤中有效态氮的含量。 相似文献
9.
采用田间小区试验,监测夏玉米不同生长期土壤水分和硝态氮剖面含量变化,研究不同施氮量对其时空变化及籽粒产量、水肥利用效率的影响,探讨氮肥对水肥资源高效利用的调节作用。结果表明：不同施氮处理,土壤剖面水分和硝态氮随土壤深度的变化趋势基本一致,即表层50 cm土壤水分和硝态氮含量较高且呈降低态,50-110 cm相对较低且波动较小,灌浆期二者均达到最低值;各生长期表层50 cm土壤含水量呈不施氮处理均高于施氮处理,50-110 cm土层则相反;施氮能提高土壤硝态氮含量,土壤硝态氮运移受土壤水分状况和含量的影响,含量越高,向下移动越深;施氮能显著提高水分利用效率及籽粒产量,增产效果明显（增产28.52%-37.86%）,二者均以施氮240 kg/hm^2处理最高;随施氮量的增加籽粒产量及籽粒吸氮量和水分利用效率增幅均表现为先升高后降低之趋势,当施氮量超过240 kg/hm^2后,籽粒产量和水分利用效率提高并不显著;不施氮与施氮处理氮素生产力、氮肥利用率之间均存在极显著差异。在本试验条件下,从控制土壤硝态氮积累及取得较高的产量和氮素利用率综合考虑,夏玉米的适宜施氮量范围应控制在120-240 kg/hm^2较好。 相似文献
10.
宁夏引黄灌区稻田氮素浓度变化与迁移特征 总被引：3，自引：0，他引：3
过量施氮与不合理灌水是农田面源污染加剧的主要原因。为了寻求较优的水氮管理模式以促进农业生产和减少农田退水对黄河水体的污染, 在宁夏引黄灌区典型稻田中开展了不同水氮条件下稻田氮素迁移转化规律研究。结果表明: 不同水氮条件下稻田田面水NH4+-N 与NO3--N 浓度伴随施肥出现明显峰值, NO3--N 峰值出现时间较NH4+-N 晚, 且变化较平缓。3 次追肥时期和整个生育期田面水NH4+-N 平均浓度与施氮量和灌水量都呈显著相关, 田面水NO3--N 平均浓度与施氮量呈显著正相关, 与灌水量相关性不显著。稻田30 cm与60 cm 深度的直渗水NH4+-N 浓度受施肥影响较大, 与田面水NH4+-N 浓度变化规律相似, 90 cm 处直渗水NH4+-N 浓度峰值出现较为滞后, 且浓度较上层土体低, 120 cm 处直渗水NH4+-N 浓度大体呈现持续上升趋势,整个生育期直渗水NH4+-N 平均浓度与施氮量呈显著相关, 仅30 cm 处NH4+-N 平均浓度与灌水量呈负相关, 其他土层深度不显著。30 cm 与60 cm 直渗水NO3--N 浓度在首次灌水后急剧下降, 在施肥后有较小幅度上升, 90 cm 与120 cm 直渗水NO3--N 浓度下降缓慢, 仅30 cm 处NO3--N 平均浓度与施肥量显著正相关。总的结果表明减少施肥或灌水均可达到减少农田氮素淋失的目的。 相似文献
11.
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 总被引：1，自引：1，他引：1
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. 相似文献
12.
日光温室番茄灌水量与根层硝态氮淋溶特征及渗漏关系研究 总被引：4，自引：0，他引：4
针对蔬菜灌溉水肥渗漏问题,采用田间试验和室内分析相结合,研究了番茄膜下沟灌灌水量与土壤硝态氮的根层外渗漏关系,分析了灌水量与不同根层土壤硝态氮的淋溶和保蓄特征,结果表明:灌溉不施肥条件下灌水量与土壤硝态氮淋溶量和淋溶率、灌溉施肥条件下灌水量与土壤施入硝态氮的保蓄率和渗漏率均呈直线关系;灌溉均会引起浅根层(0—20 cm)硝态氮淋溶,灌溉施肥条件下7.5～15 mm灌水量范围硝态氮积累有一个峰值,而22.5～45 mm范围则有两个峰值;灌水量在7.5～15mm之间,灌溉不施肥条件下根层土壤硝态氮淋溶率为0,灌溉施肥条件下土壤硝态氮渗漏率为0～5.19%;灌水量在22.5～45 mm之间,灌溉不施肥土壤硝态氮淋溶率为5.38%～19.08%,灌溉施肥条件下根层土壤硝态氮渗漏率为21.91%～61.96%。日光温室番茄膜下沟灌能减少肥料淋溶与渗漏的节水灌水量为15 mm。 相似文献
13.
《Soil Science and Plant Nutrition》2013,59(2):186-194
Abstract To determine the relationships between microbial biomass nitrogen (N), nitrate–nitrogen leaching (NO3-N leaching) and N uptake by plants, a field experiment and a soil column experiment were conducted. In the field experiment, microbial biomass N, 0.5 mol L?1 K2SO4 extractable N (extractable N), NO3-N leaching and N uptake by corn were monitored in sawdust compost (SDC: 20 Mg ha?1 containing 158 kg N ha?1 of total N [approximately 50% is easily decomposable organic N]), chemical fertilizer (CF) and no fertilizer (NF) treatments from May 2000 to September 2002. In the soil column experiment, microbial biomass N, extractable N and NO3-N leaching were monitored in soil treated with SDC (20 Mg ha?1) + rice straw (RS) at five different application rates (0, 2.5, 5, 7.5 and 10 Mg ha?1 containing 0, 15, 29, 44 and 59 kg N ha?1) and in soil treated with CF in 2001. Nitrogen was applied as (NH4)2SO4 at rates of 220 kg N ha?1 for SDC and SDC + RS treatments and at a rate of 300 kg N ha?1 for the CF treatment in both experiments. In the field experiment, microbial biomass N in the SDC treatment increased to 147 kg N ha?1 at 7 days after treatment (DAT) and was maintained at 60–70 kg N ha?1 after 30 days. Conversely, microbial biomass N in the CF treatment did not increase significantly. Extractable N in the surface soil increased immediately after treatment, but was found at lower levels in the SDC treatment compared to the CF treatment until 7 DAT. A small amount of NO3-N leaching was observed until 21 DAT and increased markedly from 27 to 42 DAT in the SDC and CF treatments. Cumulative NO3-N leaching in the CF treatment was 146 kg N ha?1, which was equal to half of the applied N, but only 53 kg N ha?1 in the SDC treatment. In contrast, there was no significant difference between N uptake by corn in the SDC and CF treatments. In the soil column experiment, microbial biomass N in the SDC + RS treatment at 7 DAT increased with increased RS application. Conversely, extractable N at 7 DAT and cumulative NO3-N leaching until 42 DAT decreased with increased RS application. In both experiments, microbial biomass N was negatively correlated with extractable N at 7 DAT and cumulative NO3-N leaching until 42 DAT, and extractable N was positively correlated with cumulative NO3-N leaching. We concluded that microbial biomass N formation in the surface soil decreased extractable N and, consequently, contributed to decreasing NO3-N leaching without impacting negatively on N uptake by plants. 相似文献
14.
《Communications in Soil Science and Plant Analysis》2012,43(10):1223-1235
Nitrogen (N) fertilizer use in cotton (Gossypium hirsutum L.) production is a potential source of nitrate (NO3 ?) contamination of soils, groundwater, and streams. The McConnell–Mitchell plots, a long-term study of cotton responses to N-fertilization and irrigation methods, were utilized to determine the NO3 ?-N in soil cropped to continuous cotton. The McConnell–Mitchell plots had a split-block experiential design. The main blocks of this test were irrigation methods. Each block of plots was irrigated using a single irrigation method for the entirety of the testing. Nitrogen fertilization rates were tested within each irrigation block. The soil NO3 ?-N content of two irrigation blocks, furrow flow (FI) and center pivot (CP), were compared to the dryland (DL) control block. Nitrogen treatments tested within each irrigation block ranged from 0 to 168.0 kg N ha?1 in 33.6-kg N ha?1 increments. Nitrogen treatments were tested for 18 years (1982 through 1999), discontinued for 4 years (2000 through 2003), and resumed in 2004. Soil samples were taken in the early spring (2000 and 2004) to a depth of 1.50 m in 0.15 m increments and analyzed for NO3 ?-N. Soil samples taken in 2004 were prior to any fertilization treatment. Irrigation method was found to influence the distribution of soil NO3 ?-N. Little accumulation of soil NO3 ?-N was observed in either irrigation block or under dryland production when N rates were less than 67.2 kg N ha?1. Distribution of soil NO3 ?-N in the FI block was significantly different with sample depth and N treatment but not the interaction of depth and treatment in both 2000 and 2004. Presumably, the small and close values of the means and the greater variability of interactions compared to main effects precluded significant interactions. Differences in soil NO3 ?-N in the FI block after suspending N treatments for 4 years were similar to those found in 2000, although the soil NO3 ?-N was generally depleted in 2004 compared to 2000. The distribution of soil NO3 ?-N in the CP-irrigated block was dependent on the interaction of sample depth with N treatment in both 2000 and 2004. Soil NO3 ?-N values and differences tended to be too small to be of discernable or practical importance under CP irrigation. The distribution of soil NO3 ?-N in the DL block was dependent on the interaction of sample depth with N treatment in 2000 and 2004. Soil NO3 ?-N was minimal in the three lowest N treatments (0, 33.6, and 67.2 kg N ha?1) in 2000. Greatest amounts of soil NO3 ?-N were found in conjunction with the 134.4 and 168.0 kg N ha?1 treatments both years. Depletion of soil NO3 ?-N was evident in the surface 0.45 m of the 100.8, 134.4, and 168.0 kg N ha?1 treatments under DL conditions in 2004. 相似文献
15.
Dan D. Fromme Dennis L. Coker Mark L. McFarland Jake E. Mowrer Tony L. Provin Ronnie W. Schnell 《Journal of plant nutrition》2017,40(1):23-32
Studies were conducted to evaluate response of dryland corn (Zea mays L.) along the upper Texas Gulf Coast to residual soil nitrate-nitrogen (NO3-N) measured to depths of 15, 30, and 61 cm. Residual soil NO3-N levels ranged from 3.4 to 31.6, 7.8 to 49.3, and 9.0 to 71.7 kg ha?1, respectively, in 0 to 15, 15 to 30, and 30 to 61 cm depth increments, with cumulative NO3-N ranging from 23.5 to 114.5 kg ha?1 across sites-years. Where N fertilizer was reduced due to N crediting, yields and bushel weights at all 13 site-years showed no difference from those receiving full recommended N rates. A yield response to any level of added fertilizer N above the control was observed for only 6 of 13 site-years. These results indicate a high potential for success in crediting carryover soil NO3-N to 61 cm as a means of reducing applied nitrogen fertilizer rates. 相似文献
16.
氮肥施用对环境污染影响的研究 总被引：207，自引：20，他引：207
通过田间试验和野外调查对陕西三个主要农业生态区的施氮情况及其对土壤和地下水污染的影响进行了研究。结果表明,有些高产地区由于过量施氮已在0～4米深的土层中积累了大量NO3-N,并使地下水和地表水受到不同程度的污染;在当季作物生长期间,土壤中NO3-N淋失深度和淋失量与施氮量、施氮技术、地面接水量和土壤质地有密切关系。 相似文献
17.
Rapid nitrate leaching losses due to current agricultural N management practices under the humid tropical environmental conditions
of the Pacific island of Guam may contaminate fresh and salt water resources. Potential environmental contamination of the
Northern Guam aquifer, which is overlain by shallow limestone-derived soils, is a major public concern because the aquifer
is the sole underground source of fresh water for the island. The objectives of this study were to examine the use of waste
office paper as a possible management alternative for reducing nitrate leaching due to N fertilizer applications in northern
Guam while also providing sufficient N for crop growth. In a laboratory study, increasing rates of waste paper application
reduced NO3
–-N leaching up to approximately 200 days after incorporation of N fertilizer and paper treatments. Subsequent mineralization
of immobilized N from paper applications was also observed, although cumulative NO3
–-N leaching at the highest rate of paper addition was lower than the control after 394 days of incubation. The effect of waste
paper on N availability and NO3
–-N leaching after application of N fertilizer at rates up to 500 kg N ha–1 was also evaluated in two field experiments planted with sweet corn (Zea mays var. rugosa Bonaf.) during consecutive dry and wet periods. Leaching losses of NO3
–-N were higher during the wet cropping season, leading to lower crop yields and crop N uptake. Combining paper with N fertilizer
reduced NO3
–-N leaching losses but also decreased crop ear yields up to N fertilizer application rates of 250 kg N ha–1 during the dry cropping season and up to rates of 100 kg N ha–1 during the wet period. Although combining waste paper with N fertilizer reduced NO3
–-N leaching losses, no improvements in fertilizer N recovery were observed during the field experiments. This lack of crop
response may be due to the importance of early season N availability for the short-season horticultural crops grown on Guam.
We suggest that the application of waste paper may be a useful management practice to reduce NO3
–-N leaching losses when high soil NO3
–-N levels remain after cropping due either to crop failure or to over-application of N fertilizer.
Received: 11 May 1999 相似文献
18.
Optimal fertilizer nitrogen (N) rates result in economic yield levels and reduced pollution. A soil test for determining optimal fertilizer N rates for wheat has not been developed for Quebec, Canada, or many other parts of the world. Therefore, the objectives were to determine: 1) the relationship among soil nitrate (NO? 3)- N, soil ammonium (NH + 4)- N and N fertilizer on wheat yields; and 2) the soil sampling times and depths most highly correlated with yield response to soil NO? 3-N and NH + 4-N. In a three year research work, wet and dried soil samples of 0- to 30- and 30- to 60-cm depths from 20 wheat fields that received four rates of N fertilizer at seeding and postseeding (plants 15 cm tall) were analyzed for NH + 4-N and NO? 3 -N using a quick-test (N-Trak) and a standard laboratory method. Wheat yield response to N fertilizer was limited, but strong to soil NO? 3-N. 相似文献
19.
肥液浓度对单膜孔入渗NO-3-N运移特性影响的室内试验研究 总被引：5，自引：0，他引：5
该文通过室内入渗试验，研究了不同浓度的单膜孔肥液入渗NO-3-N的分布特性。研究表明：不同浓度的膜孔肥液入渗土壤NO-3-N浓度的湿润锋运移距离与土壤水分运动的湿润锋一致；肥液浓度越大，相同入渗时间的NO-3-N浓度锋运移距离越大，土壤剖面NO-3-N浓度最大值越大，相同深度处土壤NO-3-N浓度也越大。肥液入渗土壤NO-3-N浓度分布特征与湿润体深度符合分段函数模型。供水入渗过程中，NO-3-N浓度锋运移距离和浓度最大值均随时间的延长而增大；再分布过程中，NO-3-N浓度锋运移距离继续增大，而NO-3-N浓度最大值逐渐减小。 相似文献
20.
Subsoil acidity restricts root growth and reduces crop yields in many parts of the world. More than half of the fertilizer nitrogen(N) applied in crop production is currently lost to the environment. This study aimed to investigate the effect of gypsum application on the efficiency of N fertilizer in no-till corn(Zea mays L.) production in southern Brazil. A field experiment examined the effects of surface-applied gypsum(0, 5, 10, and 15 Mg ha~(-1)) and top-dressed ammonium nitrate(NH_4NO_3)(60, 120, and 180 kg N ha~(-1)) on corn root length, N uptake, and grain yield. A greenhouse experiment was conducted using undisturbed soil columns collected from the field experiment site to evaluate NO_3-N leaching, N uptake, and root length with surface-applied gypsum(0 and 10 Mg ha~(-1)) and top-dressed NH_4NO_3(0 and 180 kg N ha~(-1)). Amelioration of subsoil acidity due to gypsum application increased corn root growth,N uptake, grain yield, and N use efficiency. Applying gypsum to the soil surface increased corn grain yield by 19%–38% and partial factor productivity of N(PFPN) by 27%–38%, depending on the N application rate. Results of the undisturbed soil column greenhouse experiment showed that improvement of N use efficiency by gypsum application was due to the higher N uptake from NO_3-N in the subsoil as a result of increased corn root length. Our results suggest that ameliorating subsoil acidity with gypsum in a no-till corn system could increase N use efficiency, improve grain yield, and reduce environmental risks due to NO_3-N leaching. 相似文献