玉米-大豆间作和减量施氮对玉米生长、产量及土壤硝态氮含量的影响

通过大田试验，研究玉米单作（MM）、玉米-大豆间作1∶2（IMS1，玉米1行，大豆2行）、2∶2（IMS2，玉米2行，大豆2行）3种种植方式和3种施肥水平不施氮（N0）、减量施氮200 kg/hm（N1）、常量施氮300 kg/hm（N2）对玉米生长、产量以及土壤硝态氮含量的影响。结果表明，IMS1下，N2玉米叶面积较N0显著提高6.30%。间作和N1处理对玉米产量无显著影响，但显著提高了玉米和大豆总产量。N1较N2的氮肥农学效率显著提高。土壤硝态氮随玉米不同生育期的变化而变化，在成熟期达到最低值。与N2相比，N1土壤硝态氮无显著变化，未对土壤养分产生负面影响并能满足作物对氮素的需求，保持高产。总体来看，玉米大豆间作模式下减量施氮有利于节肥和提高间作体系总产量。     

Carbon,nitrogen and phosphorus leaching after site preparation at a boreal forest clear-cut area

Clear-cutting followed by mechanical site preparation is the major disturbance influencing nutrient and water fluxes in Fennoscandian boreal forests. The effects of soil harrowing on the fluxes of dissolved organic carbon (DOC), dissolved nitrogen compounds (organic N, NH₄⁺ and NO₃⁻) and water soluble phosphorus (PO₄³⁻) through a podzolic soil were studied in a clear-cut in eastern Finland for 5 years. The old, mixed coniferous stand was clear-cut and stem only harvested in 1996 followed by soil harrowing in 1998 and planting in June 1999. Zero-tension lysimeters were used to collect soil water from below different soil horizons in the three types of microsites that resulted from site preparation treatment: low ridges (25% of clear-cut area), shallow furrows (30%) and the undisturbed soil (45%). After soil harrowing, the leaching of DOC, N and P from below the B-horizon increased compared to pre-treatment levels. However, the increases were short-lasting; 1–2 years for inorganic N and P, and 5 years for DOC and organic N. The highest concentrations were associated with the ridges and lowest with the furrows, reflecting the differences in amount of organic matter present in each microsite type and, for N, to enhanced mineralization and nitrification. Leaching from below the B-horizon over the 5 years following soil harrowing for the whole clear-cut area was 36.5 kg ha⁻¹ for DOC, 0.88 kg ha⁻¹ for NH₄-N, 0.46 kg ha⁻¹ for NO₃-N, 1.24 kg ha⁻¹ for organic N and 0.09 kg ha⁻¹ for PO₄-P. Site preparation increased temporarily the risk for nutrient leaching into watercourses and groundwater from the clear-cut area but soil fertility was not affected since the leached amounts remained small. The main reasons for the observed low leaching values were the rapid recovery of ground vegetation and low N deposition loads.     

Effects of strip wise tillage in combination with liming on chemical and physical properties of acidic spruce forest soils after clear cutting

We investigated the initial effects of strip wise soil loosening (0–35 cm depth) on soil chemical and physical parameters by using a deeply working rotary cultivator in combination with liming and mixing of the dolomite with the soil material of acidic forests. The investigations took place 8 months after the treatment. pH values and contents of exchangeable Ca and Mg increased significantly at the tilled depth whereas the content of exchangeable Al and easily soluble P decreased. The rate of mineralisation increased at this depth which was shown by a loss of Corg, Ntot and short-term loss of NO₃-N. The treatment led to a mobilisation of Mn at the tilled depth. However, the content of exchangeable Pb decreased due to an increased pH value. Below the tillage depth of 35 cm only partly significant changes of exchangeable Mn and NO₃-N were found. The total porosity and bulk density at 10–15 and 40–45 cm depths were not significantly different from those in the control plot, but the rate of infiltration increased significantly.     

Nitrate reductase activity and its diurnal variation rhythm for Camptotheca acuminata seedlings

Nitrate reductase activity (NRA) in different plant organs and leaves in different positions of Camptotheca acuminata seedlings was determined by an In vivo assay, the diurnal variation rhythm of NRA in leaves of different positions was observed,and the correlations between leaf NRA, leaf area and lamina mass per unit area (LMA) were also examined. The results showed that NRA in the leaf was significantly highest, compared with that in other organs such as roots, stems and leaves. In this experiment, the 10 leaves were selected from the apex to the base of the seedlings in order. The different NRA occurred obviously in leaves of different positions of C. acuminata seedlings from the apex to the base, and NRA was higher in the 4th-6th leaves.The diurnal change rhythm of leaf NRA showed a one peak curve, and maximum NRA value appeared at about midday (at 12:30 or so). No obvious correlations between NRA and leaf area or lamina mass per unit area were observed. This study offered scientific foundation for the further research on nitrogen metabolism of C. acuminata.     

覆膜方式对旱作玉米硝态氮时空动态及氮素利用效率的影响

以提高玉米氮素利用效率、减少氮肥污染为目标,在甘肃省定西市李家堡设置了露地(NM)、半膜平作(HM)、全膜平作(CM)和全膜双垄(CMRF)沟播等田间试验处理,对其土壤剖面中NO3- -N的积累强度、玉米干物质积累及氮素利用效率进行了系统研究.结果表明:整个生育期覆膜处理在0～ 10 cm表层中NO3- -N浓度最高,...     

The effect of situational variability in climate and soil, choice of animal type and N fertilisation level on nitrogen leaching from pastoral farming systems around Lake Taupo, New Zealand

Agricultural systems with grazing animals are increasingly under scrutiny for their contribution to quality degradation of waterways and water bodies. Soil type, climate, animal type and nitrogen (N) fertilisation are contributors to the variation in N that is leached through the soil profile into ground and surface water. It is difficult to explore the effect of these factors using experimentation only and modelling is proposed as an alternative. An agro-ecosystem model, EcoMod, was used to quantify the pastoral ecosystem responses to situational variability in climate and soil, choice of animal type and N fertilisation level within the Lake Taupo region of New Zealand. Factorial combinations of soil type (Oruanui and Waipahihi), climate (low, moderate and high rainfall), animal type (sheep, beef and dairy) and N fertilisation level (0 or 60 kg N/ha/yr) were simulated. High rainfall climates also had colder temperatures, grew less pasture and carried fewer animals overall which lead to less dung and urinary N returned. Therefore, even though a higher proportion of N returned ultimately leached at the higher rainfall sites, the total N leached did not differ greatly between sites. Weather variation between years had a marked influence on N leaching within a site, due to the timing and magnitude of rainfall events. In this region, for these two highly permeable soil types, N applied as fertiliser had a high propensity to leach, either after being taken up by plants, grazed and returned to the soil as dung and urine, or due to direct flow through the soil profile. Soil type had a considerable effect on N leaching risk, the timing of N leaching and mean pasture production. Nitrogen leaching was greatest from beef cattle, followed by dairy and sheep with the level of leaching related to urine deposition patterns for each animal type and due to the amount of N returned to the soil as excreta. Simulation results indicate that sheep farming systems with limited fertiliser N inputs will reduce N leaching from farms in the Lake Taupo catchment.     

Effect of tile effluent on nutrient concentration and retention efficiency in agricultural drainage ditches

Tile drainage is a common water management practice in many agricultural landscapes in the Midwestern United States. Drainage ditches regularly receive water from agricultural fields through these tile drains. This field-scale study was conducted to determine the impact of tile discharge on ambient nutrient concentration, nutrient retention and transport in drainage ditches. Grab water samples were collected during three flow regimes for the determination of soluble phosphorus (SP), ammonium nitrogen (NH₄⁺-N), nitrate nitrogen (NO₃-N) concentrations and their retention in three drainage ditches. Measured nutrient concentration indicated lower SP and NH₄⁺-N, and greater NO₃-N concentrations in tile effluents compared to the ditch water. Net uptake lengths were relatively long, especially for NO₃-N, indicating that nutrients were generally not assimilated efficiently in these drainage systems. Results also indicated that the study reaches were very dynamic showing alternating increases or decreases in nutrient concentration across the flow regimes. The drainage ditches appeared to be nutrient-rich streams that could potentially influence the quality of downstream waters.     

Cover crop effects on nitrogen load in tile drainage from Walnut Creek Iowa using root zone water quality (RZWQ) model

Studies quantifying winter annual cover crop effects on water quality are mostly limited to short-term studies at the plot scale. Long-term studies scaling-up water quality effects of cover crops to the watershed scale provide more integrated spatial responses from the landscape. The objective of this research was to quantify N loads from artificial subsurface drainage (tile drains) in a subbasin of the Walnut Creek, Iowa (Story county) watershed using the hybrid RZWQ-DSSAT model for a maize (Zea mays L.)-soybean [Glycine max (L.) Merr.] and maize-maize-soybean rotations in all phases with and without a winter wheat (Triticum aestivum L.) cover crop during a 25-year period from 1981 to 2005. Simulated cover crop dry matter (DM) and N uptake averaged 1854 and 36 kg ha⁻¹ in the spring in the maize-soybean phase of the 2-year rotation and 1895 and 36 kg ha⁻¹ in the soybean-maize phase during 1981-2005. In the 3-year rotation, cover crop DM and N uptake averaged 2047 and 44 kg ha⁻¹ in the maize-maize-soybean phase, 2039 and 43 kg ha⁻¹ in the soybean-maize-maize phase, and 1963 and 43 kg ha⁻¹ in the maize-soybean-maize phase during the same period. Annual N loads to tile drains averaged 29 kg ha⁻¹ in the maize-soybean phase and 25 kg ha⁻¹ in the soybean-maize phase compared to 21 and 20 kg ha⁻¹ in the same phases with a cover crop. In the 3-year rotation, annual N loads averaged 46, 43, and 45 kg ha⁻¹ in each phase of the rotation without a cover crop and 37, 35, and 35 kg ha⁻¹ with a cover crop. These results indicate using a winter annual cover crop can reduce annual N loads to tile drains 20-28% in the 2-year rotation and 19-22% in the 3-year rotation at the watershed subbasin scale over a 25-year period.     

Optimized denitrification bioreactor treatment through simulated drainage containment

In the design of wood-based, enhanced-denitrification bioreactors to treat nitrate in agricultural drainage, the consideration of the highly variable flow rates and nitrate concentrations inherent to many drainage systems is important. For optimized mitigation of these nitrate loads, it may be best to contain drainage water prior to treatment in order to facilitate longer, more constant retention times rather than to allow cycles of flushing and dry periods in the denitrification bioreactor. Simulated containment prior to bioreactor treatment compared to passing drainage directly through a bioreactor was investigated with the use of six pilot-scale denitrification bioreactors constructed with plywood and filled with Pinus radiata woodchips at Massey University No. 4 Dairy Farm (Palmerston North, New Zealand). Initial bromide tracer tests were followed with a series of five simulated drainage events each at successively declining inflow nitrate concentrations. During each drainage event, three pilot bioreactors received a simulated hydrograph lasting 1.5 days (Non-Containment treatment) and three pilot bioreactors received the same total drainage volume treated over 4 days at a constant flow rate (i.e. constant retention time; Containment treatment). Results showed significantly different total mass removal efficiencies of 14.0% vs. 36.9% and significantly different removal rates of 2.1 g N m⁻³ day⁻¹ vs. 6.7 g N m⁻³ day⁻¹ for the Non-Containment and Containment treatments, respectively, which indicated that treating drainage at constant retention times provided more optimized nitrate removal. While this work was done to evaluate treatment under New Zealand drainage conditions, it also provides valuable information for optimizing agricultural drainage denitrification bioreactor performance in general.     

甜菜子叶期幼苗硝态氮吸收特性及其与硝酸还原酶活性的关系

６个有代表性的甜菜品种在人工气候室的营养液培养试验表明，甜菜子叶期幼苗对ＮＯ３＾－的吸收要经最初２ｈ的适应阶段后才可均匀进行。均匀吸收后，观察到多倍体的吸收量〉２倍体，倍性相同品种中Ｅ型〉ＮＥ型〉ＮＺ型〉Ｚ型的初步结果。不同类型品种间ＮＯ３＾－吸收的表观米氏常数（Ｋｍ，ａｐｐ）、最大吸收速率（Ｉｍ）有明显差异，除多倍体ＮＺ型品种甜研３０１的Ｋｍ，ａｐｐ较低而Ｉｍ较高外，其余品种的Ｋｍ，ａｐｐ和Ｉｍ