Nitrate leaching in a silage maize field under different irrigation and nitrogen fertilizer rates

Quantification of the interactive effects of nitrogen (N) and water on nitrate (NO₃) loss provides an important insight for more effective N and water management. The goal of this study was to evaluate the effect of different irrigation and nitrogen fertilizer levels on nitrate-nitrogen (NO₃-N) leaching in a silage maize field. The experiment included four irrigation levels (0.7, 0.85, 1.0, and 1.13 of soil moisture depletion, SMD) and three N fertilization levels (0, 142, and 189 kg N ha⁻¹), with three replications. Ceramic suction cups were used to extract soil solution at 30 and 60 cm soil depths for all 36 experimental plots. Soil NO₃-N content of 0-30 and 30-60-cm layers were evaluated at planting and harvest maturity. Total N uptake (NU) by the crop was also determined. Maximum NO₃-N leaching out of the 60-cm soil layer was 8.43 kg N ha⁻¹, for the 142 kg N ha⁻¹ and over irrigation (1.13 SMD) treatment. The minimum and maximum seasonal average NO₃ concentration at the 60 cm depth was 46 and 138 mg l⁻¹, respectively. Based on our findings, it is possible to control NO₃ leaching out of the root zone during the growing season with a proper combination of irrigation and fertilizer management.     

Modulation of sodium channels by the oxadiazine insecticide indoxacarb and its N-decarbomethoxylated metabolite in rat dorsal root ganglion neurons

The effects of the oxadiazine insecticide indoxacarb and its N-decarbomethoxylated metabolite (DCJW) on tetrodotoxin-resistant (TTX-R) voltage-gated sodium channels in rat dorsal ganglion neurons were studied using the whole-cell patch clamp technique. Indoxacarb and DCJW suppressed the peak amplitude of action potentials, and DCJW exhibited a faster time course and higher potency than indoxacarb in the blocking effects. In voltage-clamp experiments, indoxacarb and DCJW suppressed TTX-R sodium currents in a time-dependent manner without a steady-state level of suppression. IC50 values for indoxacarb and DCJW on TTX-R sodium currents were estimated to be 10.7 and 0.8 microM after 25 min of bath application, respectively. DCJW was about 10 times more potent than indoxacarb in blocking TTX-R sodium currents. Although the suppressive effects of indoxacarb were partially reversible after washout with drug-free external solution, no recovery of sodium current was observed in DCJW treated neurons after prolonged washout. In current-voltage relationships, both indoxacarb and DCJW blocked the sodium currents to the same degree in the entire range of membrane potentials. The sodium conductance-voltage curve was not shifted along the voltage axis by indoxacarb and DCJW at 10 microM. In contrast, the steady-state inactivation curves were shifted in the hyperpolarizing direction by indoxacarb as well as by DCJW. Based on these results, it was concluded that indoxacarb and DCJW potently blocked the TTX-R sodium channel in rat DRG neurons with hyperpolarizing shifts of the steady-state inactivation curves, suggesting preferential association of the insecticides to the inactivated state of sodium channels. The small structural variation between indoxacarb and DCJW resulted in clear differences in potency for blocking sodium channels and reversibility after washout.     

有机土基质栽培对生姜产量及氮磷钾利用效率的影响

为提高生姜有机土基质栽培的肥料利用效率,设土壤栽培不施肥（CK1）和常规土壤栽培（CK2）两个对照,研究了有机土基质栽培不施肥（T1）、有机土基质栽培与土壤栽培等量施肥（T2）、有机土基质栽培与按目标产量需肥量施肥（T3）对生姜生长及氮磷钾吸收利用特性的影响。结果表明,生姜植株生长量以T2、T3较高,T1较低,CK2居中,T1的生物产量、经济产量分别比CK2降低27.63%、23.01%,而T2、T3则分别比CK2提高17.46%、15.36%和11.05%、13.04%|T2的生物产量显著高于T3,但经济产量则与T3无显著差异。生姜对氮（N）、磷（P2O5）、钾（K2O）利用率以T3较高,分别达35.11%、22.81%和46.25%,较CK2分别高7.31个百分点、3.65个百分点和14.98个百分点|T3的氮、钾利用率也显著高于T2,但二者对磷的利用率无显著差异。生姜肥料农学效率及偏生产力均以T3较高,分别达14.46 kg?kg-1和45.34 kg?kg-1,而T2和CK2仅分别为10.26、30.86 kg?kg-1和11.25、26.75 kg?kg-1。表明生姜有机土基质栽培适量施用速效化肥有利于提高肥效和生产能力。     

Impact of long-term N fertilization on the structural composition of spruce litter and mor humus

The aims of this study were to determine the degree of lignin degradation and to investigate changes in the chemical composition of the organic matter in the forest floor in an N fertilized Norway spruce forest soil. Needle litter and mor humus were collected from the field experiment at Skogaby in southern Sweden (56°33′N; 13°13′E). The spruce stand had been fertilized for 11 years with 100 kg N ha⁻¹ yr⁻¹ as (NH₄)₂SO₄. The degree of lignin degradation was determined with alkaline CuO oxidation followed by HPLC analysis. The chemical composition of the organic matter was characterized by CPMAS ¹³C NMR. Tannin was specifically analyzed using dipolar dephasing CPMAS ¹³C NMR and the N distribution was studied by CPMAS ¹⁵N NMR.The C-to-N ratios in the fertilized Oi and Oe layers were significantly lower than in the unfertilized layers (24 compared to 34 and 23 compared to 27, respectively). Neither the sum of the CuO oxidation products (Vanillyls+Syringyls+Cinnamyls expressed as VSC) nor the acid-to-aldehyde ratio ((Ac/Al)_V) showed any significant treatment effects. The content of aromatic C (including phenolic C) was significantly lower in the unfertilized than in the fertilized Oi layer (18 versus 21%). In the unfertilized soil, VSC was positively correlated (r=+0.63, p<0.05) with the C-to-N ratio, whereas the phenolic C content was negatively correlated (r=−0.61, p<0.05). The tannin index showed a tendency of increasing from Oi to Oe layers in both treatments. Most of the organic N was found as amide-N, whereas no heterocyclic N was detected. We have not been able to show any major C structural changes due to N fertilization. We suggest that the significantly higher content of aromatic and phenolic C in the fertilized Oi layer is due to an initial stimulation of the microbial community.     

不同氮磷配比对旱作土壤养分和油葵产量的影响

采用调查分析、田间试验等方法,研究了旱作土壤条件下油用向日葵氮磷肥的吸肥特性和对氮磷肥的吸收规律。结果表明:不同厚度(0～20cm)和(20～40cm)的土壤对养分的吸收呈现动态的变化特点,施氮270.0kg/hm2时吸收氮素分别为47.5和35.7mg/kg,相差24.8%;油葵产量为2 604.0kg/hm2,施磷100.05kg/hm2时吸收磷素分别为28.4和21.5mg/kg,相差24.2%,油葵产量为3 199.5kg/hm2。     

The effect of the nitrification inhibitor dicyandiamide (DCD) on spring and annual herbage production in urine patches when applied in late summer or early autumn

A cut plot experiment was undertaken at two sites in Ireland, one a free‐draining acid brown earth at Moorepark (MPK) and the other a fine loam soil with imperfect drainage at Johnstown Castle (JC). The effect of applying the nitrification inhibitor dicyandiamide (DCD) at 10 kg ha^?1 in July, August and September or not applying DCD to plots receiving synthetic urine or zero urine on spring and annual herbage production was examined. In the experiment, each site received 350 kg nitrogen (N) fertilizer ha^?1 year^?1. The application of DCD in August at a rate of 10 kg ha^?1 significantly increased spring and annual herbage production by 14 and 15%, respectively, at MPK, when applied following urine application in year 1. There was no effect of DCD applied in year 1 on herbage production at JC. The application of DCD in August resulted in lower soil total oxidized N (TON) content up to sampling day 56 post‐urine application, at MPK in year 1, retaining higher N content in the soil. There was no effect of DCD on any of the parameters measured in year 2 at MPK or at JC. Urine application did not increase spring herbage production at either site. Urine application significantly increased annual herbage production at MPK only in year 1. Urine application increased annual herbage N uptake, herbage crude protein (CP) content and soil mineral N at both sites in both years.     

Achieving legislation requirements with different nitrogen fertilization strategies: Results from a long term experiment

The Nitrates Directive (91/676/EEC, Anonymous, 1991) was developed in Europe to limit environmental threats from intensive livestock farming and N fertilizer applications to crops. It imposed several rules on farmers and public bodies, one of which was nutrient fertilization plan adoption. Here we use results from the Tetto Frati (Northern Italy) Long-Term Experiment to verify the terms and coefficients in the official Italian guidelines and evaluate the limitations imposed to organic fertilization amounts. For this purpose, we mined long-term experimental data of crop yield, N uptake, N use efficiency, and soil organic matter content from miscellanea cropping systems fertilized with farmyard manure (FYM) and bovine slurry (SLU), typical of a dairy farm in Northern Italy. N fertilization efficiency indicators (Removal to Fertilizer ratio, Apparent Recovery and Nitrogen Fertilizer Replacement Value) indicated that in the long run, FYM behaved similarly to urea, and better than SLU. Even N supply rates as high as 250 kg N ha⁻¹ were justified by high rates of crop removal. In fact, among the terms of the mass-balance equation, SOM mineralization was found to be most relevant, followed by meadow rotation residual effects. We conclude that a revised Nitrates Directives application scheme could be more relaxed in its application limit of manure-N, but should be more ambitious in setting efficiency coefficients for manure fertilization.     

植物残体施用对土壤排放N2O的影响

用室内培养实验，研究正常温度（20℃）和正常水分（25％）条件下，植物残体施用对土壤N2O排放规律和排放量的影响。结果表明，植物残体施用显著影响土壤N2O排放，不同处理之间土壤N2O排放量存在较大差异。相关分析结果表明，各处理N2O排放量与植物残体的C／N呈显著负相关，与土壤中微生物活性及C,N含量呈显著正相关。各处理化肥的N2O排放系数与植物残体的C／N比呈显著负相关。     

草本花卉基质育苗技术

播种及育苗在草本花卉栽培过程中起着至关重要的作用,在育苗过程中采用基质播种及穴盘育苗技术,注意做好基质消毒,控制好温度和光照,加强肥水管理和病虫害防治,可大大提高育苗的成活率、整齐度和抗逆性,育出壮苗.     

有机,无机态氮肥及施用方法对水稻吸收土壤氮素的影响

两年盆栽试验的结果表明,1.在淹水土壤中施用硝酸钾和尿素(1986),均有促进水稻吸收土壤氮素的作用,分别比不施肥的对照增加3.4％～12.7％和13、0％～28.9％,尿素的效果优于硝酸钾。这两者深施或混施的促进作用均对应优于其表面匀施。2.施用尿素和豆科绿肥箭舌豌豆(1987)后,水稻吸收的土壤氮素,随生育期的进展而不断增加。从六叶期到完全成熟期,水稻吸收的土壤氮占其吸收全氮的百分数,施用尿素的从21.9增至31.0,施用箭舌豌豆的从26.4增至40.8。3.在整个生育期,施用尿素和箭舌豌豆的水稻吸收土壤氮素的绝对量,均高于不施肥的对照。箭舌豌豆促进水稻增加吸收土壤氮素的作用优于尿素。4.淹水植稻,不论有否施用化学氮肥或施用何种形态的氮,都会发生土壤原始氮素的损失;但合理施用有机肥料有利于土壤原始氮素的维持,以及土壤的培肥。