Effect of Deep Placement of Slow-release Fertilizer (Lime Nitrogen) Applied at Different Rates on Growth, N2 Fixation and Yield of Soya Bean (Glycine max [L.] Merr.)

A new fertilization method with deep placement of slow‐release N fertilizers, such as coated urea and lime nitrogen (LN) (calcium cyanamide) at 20 cm depth was found to promote soy bean seed yield. In the present study, the effect of deep placement of LN was investigated on different parameters such as growth, N accumulation, N₂ fixation activity and yield of soy bean by applying LN at different rates in the rotated paddy field of Niigata, Japan. In addition to the basal fertilizer, ammonium sulphate (16 kg N ha^?1), deep placement of LN was conducted by applying various amounts such as 50 kg N ha^?1 (A50), 100 kg N ha^?1 (A100) and 200 kg N ha^?1 (A200) at 20 cm depth in separate plots. A ¹⁵N‐labelled LN fertilizer was also employed for each of the above treatments to calculate N utilization from LN in separate plots. Soya bean plant growth and N₂ fixation activity were periodically analysed. Both plant growth and N accumulation were found to increase with LN treatment compared with control plants. An increase in N₂ fixation activity was found in the A100 plots. The total seed yield was the highest in the deep placement of LN with A100 (73 g per plant) compared with other treatments. The visual quality of harvested seeds also showed that A100 enhanced the quality of seeds compared with other treatments. Thus, it is suggested that N fertilization management with particular reference to optimum amount of fertilizers is important for maximum growth, N₂ fixation and enhancement of seed yield of soy bean.     

Effect of Different Crop Densities of Winter Wheat on Recovery of Nitrogen in Crop and Soil within the Growth Period

Previous experiments have shown that, at harvest of winter wheat, recovery of fertilizer N applied in early spring [tillering, Zadok’s growth stage (GS) 25] is lower than that of N applied later in the growth period. This can be explained by losses and immobilization of N, which might be higher between GS 25 and stem elongation (GS 31). It was hypothesized that a higher crop density (i.e. more plants per unit area) results in an increased uptake of fertilizer N applied at GS 25, so that less fertilizer N is subject to losses and immobilization. Different crop densities of winter wheat at GS 25 were established by sowing densities of 100 seeds m^–2 (S_low), 375 seeds m^–2 (S_cfp= common farming practice) and 650 seeds m^–2 (S_high) in autumn. The effect of sowing density on crop N uptake and apparent fertilizer N recovery (aFNrec = N in fertilized treatments ? N in unfertilized treatments) in crops and soil mineral N (N_min), as well as on lost and immobilized N (i.e. non‐recovered N = N rate ? aFNrec), was investigated for two periods after N application at GS 25 [i.e. from GS 25 to 15 days later (GS 25 + 15d), and from GS 25 + 15d to GS 31] and in a third period between GS 31 and harvest (i.e. after second and third N applications). Fertilizer N rates varied at GS 25 (0, 43 and 103 kg N ha^–1), GS 31 (0 and 30 kg N ha^–1) and ear emergence (0, 30 and 60 kg ha^–1). At GS 25 + 15d, non‐recovered N was highest (up to 33 kg N ha^–1 and up to 74 kg N ha^–1 at N rates of 43 and 103 kg N ha^–1, respectively) due to low crop N uptake after the first N dressing. Non‐recovered N was not affected by sowing density. Re‐mineralization during later growth stages indicated that non‐recovered N had been immobilized. N uptake rates from the second and third N applications were lowest for S_low, so non‐recovered N at harvest was highest for S_low. Although non‐recovered N was similar for S_cfp and S_high, the highest grain yields were found at S_cfp and N dressings of 43 + 30 + 60 kg N ha^–1. This combination of sowing density and N rates was the closest to common farming practice. Grain yields were lower for S_high than for S_cfp, presumably due to high competition between plants for nutrients and water. In conclusion, reducing or increasing sowing density compared to S_cfp did not reduce immobilization (and losses) of fertilizer N and did not result in increased fertilizer N use efficiency or grain yields.     

Fertilizers,hybrids, and the sustainable intensification of maize systems in the rainfed mid-hills of Nepal

In the rainfed mid-hill region of Nepal, most fields receive 2–3 t ha⁻¹ of organic compost application every year. Despite efficient recovery and use of organics in the mixed crop-animal systems that predominant in the mid-hills, depleted soil fertility is widely understood to be a significant constraint to crop productivity, with most farmers achieving maize grain yields below 2 t ha⁻¹. Increased use of fertilizer may arrest and even reverse long-term soil quality degradation, but few farmers in the mid-hills use them at present and existing recommendations are insufficiently responsive to site, varietal, and management factors that influence the productivity and profitability of increased fertilizer use. Moreover, policy makers and development practitioners often hold the perception that returns to fertilizer use in the mid-hills are too low to merit investment. In this study, on-farm experiments were conducted at 16 sites in the Palpa district, Nepal to assess the responsiveness of a maize hybrid (DKC 9081) and an ‘improved’ open-pollinated maize variety (‘OPV’, Manakamana-3) to four nitrogen (N) rates, i.e., 0, 60, 120 and 180 kg ha⁻¹, with each N rate response evaluated at 30:30 and 60:60 kg ha⁻¹ rates of phosphorus (P₂O₅) and potassium (K₂O), respectively. With sound agronomy and high rates of fertilizer (180:60:60 kg N:P₂O₅:K₂O ha⁻¹), grain yields observed in the field experiments exceeded 8 t ha⁻¹ with hybrids and 6 t ha⁻¹ with OPV. Yield levels were lower for OPV than hybrid at every level of applied N, but both genotypes responded linearly to N with partial factor productivity for N (PFP_N) ranging from 14 to 19 for OPV versus 26–30 for hybrid, with improved N efficiencies obtained when P and K rates were significantly higher. Averaged across phosphorus (P) and potassium (K) levels, a $ 1 incremental investment in fertilizer increased the gross margin (GM) by $ 1.70 ha⁻¹ in OPV and by $ 1.83 ha⁻¹ in the hybrid. For the full response of N, requires higher rate of P₂O₅:K₂O and vice-versa and full response to P₂O₅:K₂O does not occur if N is absent. These results suggest that, i) degraded soils in the mid-hills of Nepal respond favorably to macronutrient fertilizers – even at high rates, ii) balanced fertilization is necessary to optimize returns on investments in N but must be weighed against additional costs, iii) OPVs benefit from investments in fertilizer, albeit at a PFP_N that is 36–47% lower than for hybrids, and, consequently iv) hybrids are an effective mechanism for achieving a higher return on fertilizer investments, even when modest rates are applied. To extend these findings across years and sites in the mid-hills, crop growth simulations using the CERES-maize model (DSSAT) were conducted for 11 districts with historical weather and representative soils data. Average simulated (hybrid) maize yields with high fertilizer rate (180:60:60 kg N:P₂O₅:K₂O ha⁻¹) ranged from 3.9 t ha⁻¹ to 7.5 t ha⁻¹ across districts, indicating a high disparity in attainable yield potential. By using these values to estimate district-specific attainable yield targets, recommended N fertilizer rates vary between 65 and 208 kg N ha⁻¹, highlighting the importance of developing domain-specific recommendations. Simulations also suggest the potential utility of using weather forecasts in tandem with site and planting date information to adjust fertilizer recommendations on a seasonal basis.     

Application of DNDC model to estimate N<Subscript>2</Subscript>O emissions from green tea fields in Japan

Heavy doses of N fertilizers are commonly applied to green tea fields in Japan, and cause large amount of nitrate leaching in ground water and emission of ammonia and nitrous oxide (N₂O) to the atmosphere. The Denitrification and Decomposition (DNDC) model was tested against experimental data on N₂O emissions from the tea field in Nishio, Aichi, Japan. There were reasonable agreements between the simulated and measured values of N₂O emissions for this site. The model was then applied for estimating the environmental impacts as affected by farm management practices, climate change, and soil properties. The model results were assessed with respect to major indicators of agro-ecosystems including crop yield, soil organic carbon sequestration, nitrate leaching loss, and N₂O emission. The results indicated that use of compost significantly reduced nitrate leaching and N₂O emissions in comparison with N fertilizer. When soil pH and texture shifted to non-acidic and coarser soil, N₂O emission increased; and a change in temperature and precipitation affected N₂O emission, nitrate leaching, and SOC sequestration. This study thus revealed the biogeochemistry model as a powerful tool in addressing the complex efficacy of the alternative farm management practices in tea fields across various climate and soil conditions.     

Effect of biogas digestate,animal manure and mineral fertilizer application on nitrogen flows in biogas feedstock production

The expansion of biogas feedstock cultivation may affect a number of ecosystem processes and ecosystem services, and temporal and spatial dimensions of its environmental impact are subject to a critical debate. However, there are hardly any comprehensive studies available on the impact of biogas feedstock production on the different components of nitrogen (N) balance. The objectives of the current study were (i) to investigate the short-term effects of crop substrate cultivation on the N flows in terms of a N balance and its components (N fertilization, N deposition, N leaching, NH₃ emission, N₂O emission, N recovery in harvested product) for different cropping systems, N fertilizer types and a wide range of N rate, and (ii) to quantify the N footprint of feedstock production in terms of potential N loss per unit of methane produced. In 2007/08 and 2008/09, two field experiments were conducted at two sites in Northern Germany differing in soil quality, where continuous maize (R1), maize–whole crop wheat followed by Italian ryegrass as a double crop (R2), and maize–grain wheat followed by mustard as a catch crop (R3) were grown on Site 1 (sandy loam), and R1 and a perennial ryegrass ley (R4) at Site 2 (sandy soil rich in organic matter). Crops were supplied with varying amounts of N (0–360 kg N ha⁻¹, ryegrass: 0–480 kg N ha⁻¹) supplied as biogas digestate, cattle slurry, pig slurry or calcium-ammonium nitrate (CAN).Mineral-N fertilization of maize-based rotations resulted in negative N balances at N input for maximum yield (Nopt), with R2 having slightly less negative balances than R1 and R3. In contrast, N balances were close to zero for cattle slurry or digestate treatments. Thus, trade-offs between substrate feedstock production and changes of soil organic matter stocks have to be taken into consideration when evaluating biogas production systems. Nitrogen losses were generally dominated by N leaching, whereas for the organically fertilized perennial ryegrass ley the ammonia emission accounted for the largest proportion. Nitrogen balance of the ryegrass ley at Nopt was close to zero (CAN) or highly positive (cattle slurry, digestate). Nitrogen footprint (NFP) was applied as an eco-efficiency measure of N-loss potential (difference of N input and N recovery) related to the unit methane produced. NFP ranged between −11 and +6 kg N per 1000 m³ methane at Nopt for maize-based rotations, without a significant impact of cropping system or N fertilizer type. However, for perennial ryegrass ley, NFP increased up to 65 kg N per 1000 m³. The loose relation between NFP and observed N losses suggests only limited suitability for NFP.     

Strategies to Improve the Use Efficiency of Mineral Fertilizer Nitrogen Applied to Winter Wheat

Recovery of fertilizer nitrogen (N) applied to winter wheat crops at tillering in spring is lower than that of N applied at later growth stages because of higher losses and immobilization of N. Two strategies to reduce early N losses and N immobilization and to increase N availability for winter wheat, which should result in an improved N use efficiency (= higher N uptake and/or increased yield per unit fertilizer N), were evaluated. First, 16 winter wheat trials (eight sites in each of 1996 and 1997) were conducted to investigate the effects of reduced and increased N application rates at tillering and stem elongation, respectively, on yield and N uptake of grain. In treatment 90‐70‐60 (90 kg N ha^?1 at tillering, 70 kg N ha^?1 at stem elongation and 60 kg N ha^?1 at ear emergence), the average values for grain yield and grain N removal were up to 3.1 and 5.0 % higher than in treatment 120‐40‐60, reflecting conventional fertilizer practice. Higher grain N removal for the treatment with reduced N rates at tillering, 90‐70‐60, was attributed to lower N immobilization (and N losses), which increased fertilizer N availability. Secondly, as microorganisms prefer NH₄⁺ to NO₃^? for N immobilization, higher net N immobilization would be expected after application of the ammonium‐N form. In a pot experiment, net N immobilization was higher and dry matter yields and crop N contents at harvest were lower with ammonium (ammonium sulphate + nitrification inhibitor Dicyandiamide) than with nitrate (calcium nitrate) nutrition. Five field trials were then conducted to compare calcium nitrate (CN) and calcium ammonium nitrate (CAN) nutrition at tillering, followed by two CAN applications for both treatments. At harvest, crop N and grain yield were higher in the CN than in the CAN treatment at each N supply level. In conclusion, fertilizer N use efficiency in winter wheat can be improved if N availability to the crops is increased as a result of reduced N immobilization (and N losses) early in the growth period. N application systems could be modified towards strategies with lower N applications at tillering compensated by higher N dressing applications later. An additional advantage is expected to result from use of nitrate‐N fertilizers at tillering.     

氮肥用量及钾肥施用对稻麦周年产量及效益的影响

为探明优化施氮量与高施氮量下不同钾肥施用处理对稻麦周年产量及效益的影响。本试验于2010年5月–2011年7月在江苏省如皋市农业科学研究所试验基地的田间稻麦轮作条件下,对常规粳稻品种镇稻11和春性中筋品种扬麦16设置了两个氮肥用量下不同钾肥用量及施用方法处理,测定稻麦周年的产量和组成因子,成熟期不同器官的氮、钾浓度和累积量,氮、钾利用效率及经济效益。试验结果表明,钾肥的施用显著提高了周年稻麦的产量,同时提高了稻麦的有效穗数、穗粒数和结实率,钾肥的利用效率和经济效益。稻麦周年钾肥(K₂O)的偏生产力(PFP)、农学效率(AE)、回收利用率(RE)和经济效益均以周年钾肥(K2O)土壤施用150 kg hm^-2 + 叶面喷施16.2 kg hm^-2 (K_S150 + K_F16.2)处理最高。氮肥用量的结果表明,相对于优化施氮量,高施氮量有利于提高水稻的氮素营养而增产,但对稻麦周年产量的影响不显著,且优化施氮量的氮肥利用效率及经济效益均高于高施氮量。因此,综合考虑土壤环境因素、经济效益和肥料资源管理,本地区最佳氮肥(N)用量为水稻200 kg hm^-2,小麦180 kg hm^-2;最佳钾肥(K₂O)用量及方法为水稻土壤施用90 kg hm^-2 + 叶面喷施9.7 kg hm^-2 (K_S90 + K_F9.7),小麦土壤施用60 kg hm^-2 + 叶面喷施6.5 kg hm^-2 (K_S60 + K_F6.5)。     

Effects of Time and Rate of Nitrogen and Phosphorus Application on the Growth and the Seed and Oil Yields of Canola (Brassica napus L.)

A field study was conducted to investigate the influence of variable rates of application of N and P fertilizers in splits at various times on the growth and the seed and oil yields of canola (Brassica napus L.) during 1995–97. Rates of fertilizer application were 0 and 0 (F0), 60 and 0 (F1), 0 and 30 (F2), 60 and 30 (F3), 90 and 60 (F4) and 120 and 90 (F5) kg N ha^?1 and kg P₂O₅ ha^?1. All the P was applied at sowing while N was applied in splits, i.e. all at sowing, half at sowing and half with first irrigation, or half at sowing and half at flowering. The responses of growth, seed yield and components of yield were consistent in both years. Increasing the rate of fertilizer application from F4 (90/60 kg N/P₂O₅ ha^?1) to F5 (120/90 kg N/P₂O₅ ha^?1) increased the leaf area index (LAI) relative to the control and to lower rates of fertilizer application. For both crops, application of 90/60 kg N/P₂O₅ ha^?1 significantly enhanced total dry matter (TDM) and seed yield. Seed yield increased mainly due to a greater number of pods per plant and seeds per seed‐pod. The time of fertilizer application did not significantly affect seed yield or components of yield in either season. Oil yield generally followed seed yield, increasing with increasing rate of fertilizer application up to 90/60 kg N/P₂O₅ ha^?1. The maximum oil contents were obtained from the control. The results show that seed and oil yields of canola were maximized at the F4 (90/60 kg N/P₂O₅ ha^?1) rate of application under the agro‐ecological conditions of Faisalabad, Pakistan.     

Effect of Phosphorus and Nitrogen Fertilization on Sunflower (Helianthus annus L.) Nitrogen Uptake and Yield

Little is known about the effect of combined phosphorus and nitrogen (P‐N) fertilization on the N requirement of sunflower (Helianthus annus L.). This study was carried out to evaluate the effects of varying levels of P and N, as well as the interaction P × N, on the N uptake, yield and N apparent utilization efficiency under field conditions. Split‐plot design experiments were conducted in the mid‐western Pampas in Argentina. Four levels of N (0, 46, 92 and 138 kg N ha^?1) and three levels of P (0, 12 and 40 kg P ha^?1) were applied to two Typic Hapludolls over two growing seasons (1997–98 and 1998–99). N uptake and soil N‐NO₃ contents were determined at the V₇, R₅ and R₉ growth stages. The sunflower yield ranged from 2.5 to 5.0 Mg ha^?1. The total N requirement was around 45 kg N Mg^?1 grain, and this result suggests that it is not necessary to use different N requirements (parameter b) for fertilized crops when a yield response is expected. To achieve a 100 % yield maximum a N supply (soil plus fertilizer) of 181 kg N ha^?1 at P₄₀ was needed. However, at P₀, the highest yield was about 80 % of the maximum yield with a N supply (soil plus fertilizer) of 164 kg N ha^?1. P application increased the apparent use efficiency of the supplied N.     

Potassium Management for Brown Midrib Sorghum × Sudangrass as Replacement for Corn Silage in the North-eastern USA

In recent years, there has been a growing interest in brown midrib (BMR) sorghum (Sorghum bicolor (L.) Moench.) × sudangrass (Sorghum sudanense Piper) hybrids (SxS) as a replacement for silage corn (Zea mays L.) in the north‐eastern USA. Recent studies suggest it is suitable for both rotational grazing and as a hay crop and could compete with corn harvested for silage in years when wet spring conditions prevent the timely planting of corn. However, little is known about its suitability as forage for non‐lactating cows that require low potassium (K) forages to prevent health problems. Our objective was to evaluate the impact of K fertilizer management (0, 112 or 224 kg K₂O ha^?1 cut^?1) under optimum N management (112–168 kg N ha^?1 cut^?1) on yield, quality and K concentrations of BMR SxS over a 2‐year period. Field trials were established on a fine loamy, mixed, active, mesic Aeric Fragiaquepts with medium K‐supplying capacity and characteristic of a large region in New York. Potassium application did not affect dry matter yields in either of the 2 years. Averaged over 2 years, neutral detergent fibre (NDF) significantly increased with K addition with similar but non‐significant trends observed in each of the years individually. The digestibility of NDF was unaffected by K application. Crude protein (CP) concentrations showed a significant decrease with K application in 2002 and similar trends were observed in 2003, although differences were not significant at P ≤ 0.05. The changes in NDF and CP did not significantly impact forage quality expressed as milk production per megagram of silage. Potassium application increased forage K concentration up to 13 mg K kg^?1 dry matter (in the first cut in 2003). Forage Ca and Mg concentrations decreased with K addition except for the first cut in 2002 where differences between 112 and 224 kg K₂O ha^?1 treatments were not significant. Without K addition in the 2‐year period, K concentrations in the forage decreased from 23 g kg^?1 for the first cutting in 2002 to 15 g kg^?1 for the second cut in 2003. Low K forage was obtained for all second‐cut forage unless 224 kg K₂O ha^?1 cut^?1 had been added. First‐cut forage was suitable only when no additional K had been applied. These results suggest low K BMR SxS forage can be harvested from initially high K soils without loss in dry matter yield as long as no additional K is added.     

Effect of N fertilizer top-dressing on N accumulation and N2 fixation of supernodulating soybean mutant

Increased application of nitrogen (N) fertilizer top-dressing during growth is an effective option for enhancing N supply to soybean plants. SS2-2 was characterized by the superior ability of symbiotic N₂ fixation at the level of 30 kg N ha⁻¹. But, the response of nitrogen fixation ability of supernodulating soybean mutant, SS2-2, to N fertilizer application rate remains unclear. The objective of this experiment was to compare the response of N fertilizer top-dressing on N accumulation and N₂ fixation between supernodulating mutant, SS2-2, and wild-type, Sinpaldalkong 2. The effect of N fertilizer top-dressing (0.6 g N pot⁻¹ top-dressing) on the nitrogen accumulation and redistribution were compared between SS2-2 and Sinpaldalkong 2. N fertilizer top-dressing at R1 stage increase in plant dry weight, relative growth rate (RGR), net assimilation rate (NAR), nitrogen harvest index (NHI), and N redistribution (NR). SS2-2 showed highest N concentration, 65.0 mg N g DW⁻¹, followed by Sinpaldalkong 2 and En1282, and the N content per plant did not show a significant difference between SS2-2 and Sinpaldalkong 2. The N₂ fixation rate was significantly reduced by N top-dressing, but the amount of N₂ fixation was not changed due to an improved dry weight without changes of N concentration. In addition, SS2-2 showed higher NHI, NR and NRE than Sinpaldalkong 2. These results suggested that supernodulating soybean mutants, SS2-2, could be characterized by high N concentration and N₂ fixation regardless of N fertilizer top-dressing due to a higher nitrate tolerance of supernodulating mutants than that of wild-type.     

基肥配比和拔节期追氮对鲜食糯玉米籽粒物性的影响

以鲜食糯玉米品种苏玉糯5号和渝糯7号为材料研究表明,基肥配比和拔节期追氮对籽粒物性有显著影响,且基肥配比对物性参数(除脆度和黏聚性)影响大于拔节期追氮。物性参数中,黏着性、脆度和咀嚼度变异系数较高。基肥处理中,总体上以氮磷钾肥合理配比(N 75 kg hm^-2 + P₂O₅ 75 kg hm^-2 + K₂O 75 kg hm^-2)时硬度、脆度、黏着性(绝对值)、弹性、黏聚性和咀嚼度较高,回复性适中。随着拔节期追氮量增加,硬度、脆度、黏聚性、咀嚼度和回复性均呈先升后降趋势,黏着性在不追氮和追氮150 kg hm^-2处理下无显著差异,但显著高于追氮300 kg hm^-2处理,弹性受拔节期追氮量影响较小。相关分析表明,硬度和脆度与弹性、黏聚性和咀嚼度显著正相关。黏着性与弹性、咀嚼度显著负相关,与回复性显著正相关。弹性、黏聚性和咀嚼度两两极显著正相关。综合考虑各参数的变化趋势,氮磷钾均衡基施并拔节期适量追氮时两品种籽粒具有较好的黏着性、咀嚼度和脆度,且苏玉糯5号籽粒硬度显著低于渝糯7号。     

养分管理对直播稻产量和氮肥利用率的影响

为探明不同养分管理模式在实地农户种植条件下对直播水稻产量和氮肥利用率的影响。本试验于2011年6月至2013年11月在江苏省兴化市茅山镇基本农田保护区的田间稻麦轮作条件下,分别选取茅山东村、茅山西村和冯顾村各8个农户,开展3个不同养分管理模式试验,设置了不施肥对照(CK)、农民习惯施肥(FFP)和优化施肥(OPT1和OPT2)4个处理,主要研究了水稻产量及构成因子、氮累积分配和氮肥利用率等对不同养分管理模式的响应。结果表明：(1)施肥较不施肥显著提高水稻产量,优化施肥(226 kg N hm^-2)在较习惯施肥(333 kg N hm^-2)平均减氮32.1%的基础上显著提高水稻产量5.5%,增产原因是提高了穗粒数、结实率和千粒重;OPT2较OPT1平均增产3.1%,其原因是在孕穗期增施了钾肥(18 kg hm^-2 K₂O)。(2)优化施肥水稻植株各部位氮浓度、百千克籽粒需氮量和秸秆氮累积均显著低于习惯施肥,且降低营养器官的氮素分配比例。(3)优化施肥较习惯施肥显著提高水稻氮肥利用率,其氮肥偏生产力(PFP_N)、氮肥农学效率(AE_N)、氮肥回收效率(RE_N)和氮肥生理效率(PE_N)分别平均增加55.5%、79.1%、18.7%和48.7%。(4)水稻植株氮累积与产量呈显著正相关,且优化施肥单位氮累积的增产效果高于习惯施肥。因此,基于氮肥总量控制、分期调控和增施钾肥的养分优化管理措施可在实地农户直播稻种植上协同实现水稻高产和氮肥高效。     

Effect of Timing and Nitrogen Fertilizer Application on Winter Oilseed Rape (Brassica napus L.). II. Nitrogen Uptake Dynamics and Fertilizer Efficiency

Field experiments were carried out on grey‐brown podzolic soil in the four consecutive growing seasons (1998–2001) at Krzeslice Farm, central‐western Poland. The effect of seven N fertilization treatments (in kg N ha^?1): 80_NF + 80_CAN; 80_NF + 50_CAN + 30_CN; 80_CAN + 80_CAN; 80_CAN + 80_CAN + 30_CN; 80_AN + 80_AN; 80_AN + 50_AN + 30_CN, where, NF – nitrofos NPK, CAN – calcium‐ammonium nitrate, AN – ammonium nitrate, CN – calcium nitrate and control (without N) on N uptake dynamics and N efficiency was studied. Mineral fertilizers were applied at the start of spring regrowth, beginning of stem elongation and at the flower‐bud‐visibility stage. The study revealed two distinct strategies of oilseed rape plants’ adaptation to timing and N fertilizer application sequences. Both strategies based on nitrogen uptake rate (NUR), were analysed at different plant growth stages. Ammonium nitrate (AN) applied in the two‐split system gave the highest NUR (387 mg m^?2 day^?1) during stem elongation (for comparison, a value of 166 mg m^?2 day^?1 was obtained in the control). In the case of calcium‐ammonium nitrate (CAN), a moderate level of NUR was obtained (304 mg m^?2 day^?1) but N uptake lasted 12 days longer compared with the AN treatment. Hence, N accumulation in leaves at the end of flowering explained about 81 % of yield variability. The second adaptation strategy was attributed to the three‐split N treatment. Plants fertilized with AN and CAN fertilizers showed an inconsistent pattern of NUR with time. Nitrogen accumulation in stems at the beginning of maturity, explained 69 % of yield variability. Nitrogen‐use efficiency did not show any response to N treatments.     

基肥配比和拔节期追氮对糯玉米淀粉胶凝和回生特性的影响

以苏玉糯4号为材料,采用二因素裂区设计,研究了不同基肥配比(纯N 75 kg hm^-2、纯N 75 kg hm^-2+K₂O 70 kg hm^-2、纯N 75 kg hm^-2+P₂O₅ 65 kg hm^-2和纯N 75 kg hm^-2 +P₂O₅ 65 kg hm^-2+K₂O 70 kg hm^-2)和拔节期追氮(0、150和300 kg hm^-2)对糯玉米淀粉胶凝和回生特性的影响。结果表明,淀粉和回生淀粉的起始温度、峰值温度和终值温度虽然受到施肥处理的影响,但总体上变异较小。热焓值受基肥配比影响较小,糊化范围和峰值指数受拔节期追氮量影响较小。在不同基肥配比处理下,糊化范围在基施氮钾时最低,氮磷钾合理配施处理下最高,峰值指数表现和糊化范围相反。在拔节期不同追氮量处理下,热焓值以追氮150 kg hm^-2时最高,追氮300 kg hm^-2或不追氮无显著差异。胶凝淀粉冷藏后发生回生,表现为转变温度、热焓值和峰值指数降低,糊化范围变宽。和仅基施氮相比,增施磷或(和)钾都可降低淀粉的回生值和回生淀粉的热焓值,拔节期追氮处理的这两项指标均劣于不追氮处理。回生值与回生淀粉的热焓值和峰值指数显著正相关,相关系数分别为0.90 (P < 0.01)和0.41 (P < 0.05); 原淀粉的热焓值与峰值指数极显著正相关, 相关系数为0.65 (P < 0.01),与回生淀粉热焓值显著正相关,相关系数0.44 (P < 0.05),与终值温度显著负相关,相关系数-0.41 (P < 0.05)。在本试验条件下,以氮磷钾均衡基施并拔节期追氮150 kg hm^-2时,淀粉胶凝和回生特性较为理想,表现为热焓值较高,回生值较低。     

Productivity and Sustainability of Cotton (Gossypium hirsutum L.)–Wheat (Triticum aestivum L.) Cropping System as Influenced by Prilled Urea, Farmyard Manure and Azotobacter

Field experiments were conducted at Indian Agricultural Research Institute, New Delhi, during 2001–2002 and 2002–2003, to study the effect of inorganic, organic and Azotobacter combined sources of N on cotton (Gossypium hirsutum L.) and their residual effect on succeeding wheat (Triticum aestivum L.) crop. The results indicated considerable increase in yield attributes and mean seed cotton yield (2.33 Mg ha^?1) with the combined application of 30 kg N and farmyard manure (FYM) at 12 Mg ha^?1 along with Azotobacter (M₄). The treatment in cotton that included FYM, especially when fertilizer N was also applied could either improve or maintain the soil fertility status in terms of available N, P and K. Distinct increase in yield attributes and grain yield of wheat was observed with the residual effect of integrated application of 30 kg N ha^?1 + FYM at 12 Mg ha^?1 + Azotobacter. Direct application of 120 kg N ha^?1 resulted 67.4 and 17.7 % increase in mean grain yield of wheat over no N and 60 kg N ha^?1, respectively. Integrated application of organic and inorganic fertilizer is therefore, recommended for higher productivity and sustainability of the cotton–wheat system.     

Impact of Phosphorus from Dairy Manure and Commercial Fertilizer on Perennial Grass Forage Production

Increased recovery and recycling of manure phosphorus (P) by crops on dairy farms is needed to minimize environmental problems. The main objective of this study was to compare P utilization by orchardgrass (Dactylis glomerata L.) and tall fescue (Festuca arundinaceae Schreb.) from dairy manure or inorganic fertilizer. The study was conducted from 1994 to 2000 at the Cornell University Baker Farm, Willsboro, NY, on a somewhat poorly drained Kingsbury clay (very–fine, illitic, mesic Aeric Epiaqualfs). The design was a split‐plot in a randomized complete block with two manure rates (16 800 and 33 600 kg ha^?1) and one nitrogen (N) fertilizer rate (84 kg N ha^?1 at spring greenup and 56 kg N ha^?1 prior to each regrowth harvest) as the main plots and grass species as subplots replicated six times. Fertilizer P [Ca(H₂PO₄)₂] was applied to the fertilizer treatment in 1995 and 1996 at 11 kg P ha^?1 year^?1. Orchardgrass P removal averaged 21 % higher than tall fescue P removal for the spring harvest, but orchardgrass averaged 24 % lower P removal than tall fescue removal for all regrowth harvests from 1995–99. Phosphorus herbage concentration in the fertilizer treatment was in the range of 1.9–2.7 g P kg^?1 compared with 2.2–5.3 g P kg^?1 in the manure treatments. Seasonal P removal ranged from as low as 9.2 kg P ha^?1 to as high as 48.5 kg P ha^?1. Morgan extractable soil P in the top 0–0.20 m remained high through 1999, with 29.1 kg P ha^?1 at the highest manure rate in tall fescue compared with 8.4 kg P ha^?1 measured in 1993 prior to the experiment. In 2000, soil P at the highest manure rate in tall fescue dropped to 10.1 kg P ha^?1, following cessation of manure application in 1998. Intensively managed harvested orchardgrass and tall fescue have the potential to remove large quantities of manure P.     

西北绿洲灌区水氮耦合对燕麦品种陇燕3号耗水特性及产量的影响

灌水和施肥,尤其是施氮肥,是调控作物生长和增加产量的两大重要技术措施,其互作是燕麦高产高效栽培中重要因素。2014—2015年连续2个生长季,在甘肃河西绿洲灌区的田间试验设3个定额灌溉和3个施氮(纯氮)水平,研究水氮耦合对陇燕3号农田0~150 cm土层耗水量、棵间蒸发、产量及水分利用效率的影响。3个灌溉处理的灌水量分别为270 mm(I_1)、337.5 mm(I_2)和405 mm(I_3),3个施氮水平分别为90 kg hm~(–2)(N_1)、120 kg hm~(–2)(N_2)和150 kg hm~(–2)(N_3)。从播种到成熟,燕麦阶段耗水强度呈先增后减趋势,抽穗至灌浆是最大耗水期,且同一施氮水平下,阶段耗水强度随灌水量增大而显著增加。在全生育期内,棵间蒸发量(E)及土壤水分蒸发量占总蒸发量的比例(E/ET)表现先降后升趋势,且相同施氮量下,拔节至灌浆期随灌水量的增大而增大,而灌浆至成熟期则随灌水量的增大而减小。相同施氮量下,燕麦产量随灌水量增加而显著增加,水分利用效率却随灌水量增加而降低。产量N_3I_3最高(5466.0~5727.5 kg hm~(–2)),N_3I_2次之(5428.5~5678.5 kg hm~(–2)),N_1I_1最低(4504.5~4804.3 kg hm~(–2));水分利用效率N_3I_2最大(12.11~12.82 kg mm~(–1) hm~(–2)),N_3I_1次之(12.04~12.63 kg mm~(–1) hm~(–2)),N_1I_3最小(9.79~10.58 kg mm~(–1) hm~(–2))。由此表明,水氮耦合对燕麦水分利用及产量具有显著互作效应。施氮量150 kg hm~(–2)、灌溉定额337.5 mm是西北绿洲灌区燕麦种植较佳的节水、高产水氮管理模式。     

The effect of succeeding crop and level of N fertilization on N leaching after break-up of grassland

Depending on soil and management, ploughing up grassland for use as arable land can lead to an increase in the release of mineralized nitrogen and a high risk of nitrogen leaching during winter. The amount of N leaching is also dependent on the N efficiency of following crops and the level of N fertilization.In a field experiment in northwest Germany permanent grassland was ploughed and used as arable land. The experiment was conducted over 2 years at three sites and investigated two main factors: (i) succeeding crops, either spring barley (and catch crop)–maize or silage maize–maize; and (ii) N-fertilization either nil or moderate (120 kg N ha⁻¹ for barley or 160 kg for maize). Plant yields, the soil mineral nitrogen (SMN) content and the nitrate leaching losses over winter were determined. On average for the 2-year period, the SMN in autumn and the nitrate leaching losses during winter for the rotation barley–maize were 76 kg ha⁻¹ SMN and 81 kg N ha⁻¹ N leaching losses, and for maize–maize they amounted to 108 and 113 kg ha⁻¹, respectively. The SMN and N leaching losses for the plots with no N fertilizer were 49 and 52 kg N ha⁻¹ and for the plots fertilized at a moderate N level they were 135 and 142 kg N ha⁻¹, respectively.We conclude that although the extent of nitrate leaching is influenced by the site conditions and management of the grassland prior to ploughing, the management after ploughing is the decisive factor. The farmer can significantly reduce nitrate leaching with his choice of succeeding crop and the amount of N fertilization.     

Leguminous Cover Crop Effects on Nitrogen Mineralization Rates and Kinetics in Soils

Soils were collected from an experimental site (initiated in 1991) at which leguminous crops were grown as natural soil cover in the interspaces of a 19‐year‐old coconut plantation. Atylosia scarabaeoides, Centrosema pubescens, Calopogonium mucunoides and Pueraria phaseoloides were grown in separate plots during the rainy season and ploughed into the soil towards the end of the monsoon (in December every year). Soil samples were collected from this site at the end of the 7th year and incubated in PVC columns at 35 ± 1°C and 0.01 MPa moisture content for 36 weeks. The soils were then leached at periodic intervals for up to 36 weeks and nitrogen (N) mineralization rates and kinetics were determined by the double exponential model. The N mineralization rates were highest during the first week and decreased with time in all soils. Soils amended (in situ ploughing) with cover crops leached 191 mg kg^–1 more NO₃^– + NO₂^–‐N than the unamended control. The per cent organic N mineralized (total and net) and the cumulative inorganic N mineralized (NO₃^– + NO₂^–‐N) varied with the amount (biomass) and type of cover crop incorporated into the soil. In general, soils amended with cover crops had greater N mineralization potentials and rate constants than the unamended control. The kinetic parameters N_oS and N_o(1 – S) and their respective rate constants h and k also varied with the amount and type of cover crops incorporated into the soil. The results further indicated that the lignin + polyphenol : N ratio of the cover crops is extremely important in predicting the rate of decomposition and N mineralization in soils.