Substance and Energy Balances in the "Static Fertilisation Experiment Bad Lauchstädt"

Data of the "Static Fertilisation Experiment Bad Lauchstädt" were used to identify the effect of different fertiliser application on yield, various energetic parameters as well as on carbon and nitrogen balance of the long-term trial in a selected time period (1991-2000). The fertiliser regimes considered, are neither mineral fertiliser nor farmyard manure (without/without), mineral NPK and no farmyard manure (NPK/without), no mineral fertiliser and 10t ha m 1 a m 1 farmyard manure (without/10), mineral NPK and 10t ha m 1 a m 1 farmyard manure (NPK/10), no mineral fertiliser and 15t ha m 1 a m 1 farmyard manure (without/15), as well as mineral NPK and 15t ha m 1 a m 1 farmyard manure (NPK/15). The farmyard manure was only applicated to root crops. The crop rotation included sugar beets, spring barley, potatoes and winter wheat. In most cases, the treatment NPK/10 yielded in the most favourable results whereas the treatment without/without was the most unfavourable one. Sugar beets were - followed by winter wheat - the most profitable crops, potatoes the most unfavourable one. The fossil energy input was highly variable; it ranged from 4.1 to 24.3GJ ha m 1 a m 1 depending on fertiliser regime and crop. The total yield (based on main products and by-products) varied from 2.1 to 20.1t dry matter ha m 1 a m 1 , corresponding to an energy output between 3.4 and 33.6GJ ha m 1 a m 1 . The energetic parameters energy gain (net energy output) and energy intensity ranged form 25.5 to 315GJ ha m 1 a m 1 and from 143 to 1824MJ GE m 1 , respectively. The carbon balances resulted the highest C gain with the exclusive mineral fertilisation (NPK/without), followed from the treatment NPK/10. The same applies for the nitrogen balances.     

Comparing the Nitrogen and Potassium Requirements of Canola and Wheat for Yield and Grain Quality

ABSTRACT

Grain yield increases (responses) of canola (oilseed rape, Brassica napus L.) and spring wheat (Triticum aestivum L.) to application of nitrogen (N) and potassium (K) fertilizers were compared in the same experiment at eight field sites over three years (2000–2002) in southwestern Australia. Four rates of N (0–138 kg N/ha as urea) and four rates of K (0–60 kg K ha^?1 as potassium chloride) were applied. Significant grain yield responses to applied N and K occurred for both crop species at all sites of the experiment, and the NxK interaction was significant. Canola required an average of 26% more applied N and 32% more applied K than wheat to produce 90% of the maximum grain yield. Applying increasing rates of K increased the rate of N required for 90% of maximum grain yield. Likewise, applying increasing rates of N increased the rate of K required for 90% of the maximum grain yield. Fertilizer K had no significant affect on the concentration of oil in canola grain or concentration of protein in both canola and wheat grain. Application of increasing rates of N decreased the concentration of oil while increasing the concentration of protein in canola grain, and increased concentration of protein in wheat grain. The NxK interaction was not significant for concentration of oil or protein in grain.     

基于决策系统模拟不同降水年型旱作冬小麦的最佳播期

冬前积温以及播前土壤墒情是旱作冬麦区播期选择的重要依据，利用模型选择不同降水年型下小麦适宜播期具有重要意义。收集山西省闻喜县旱作小麦区2009−2014年（2009、2010和2012年为枯水年，2011年和2013年为丰水年）的大田试验数据，对小麦决策系统进行品种参数校验和验证。利用校验过的决策系统模拟分析闻喜地区近36a（1980−2015年）冬小麦最佳播期变化以及不同降水年型下播期随产量的变化情况。结果表明：（1）1980−1984年，冬小麦最佳播期主要集中在9月25日前后；1985−1995年，历史最佳播期推迟至9月30日前后；1995−2015年，最佳播期推迟至10月5日前后。（2）研究期内，丰水年和平水年9月30日前后播种小麦平均产量最大，分别为4293.1kg·hm−2和4055.2kg·hm−2；枯水年10月5日前后播种小麦平均产量最高，为3334.5kg·hm−2。因此，随着气温的逐渐增高，冬小麦的历史最佳播期呈现明显后移趋势；丰水年和平水年9月30日前后播种，枯水年以10月5日前后播种为宜。     

Contribution of soluble and insoluble fractions of agricultural residues to short‐term pH changes

The retention of agricultural residues in cropping systems to maintain soil fertility is also important for the redistribution of alkalinity. In systems that adopt minimum or no‐tillage practices residue incorporation into the soil may occur slowly and the contribution of soluble and insoluble residue fractions to pH change may vary temporally and spatially. In this study we examined the contribution of whole, water soluble (70°C for 1 hour for two cycles) and insoluble fractions of canola, chickpea and wheat residues (added at 10 g kg^?1 soil) to pH change in a Podosol (Podzol; initial pH 4.5) and a Tenosol (Cambisol; initial pH 6.2) over a 59‐day incubation period. Whole residues increased pH in both soils, with the magnitude of the pH increase (chickpea > canola > wheat) being related to alkalinity content (concentration of excess cations) of the residue. Temporal release of alkalinity was only observed for the larger alkalinity content canola and chickpea residues and the change in pH was greater than during the initial period (approximately 4 hours; T0). Increases in pH were attributed to the decarboxylation of organic anions and the association of H⁺ with organic anions and other negatively charged chemical functional groups. The relative contribution of these processes depended on the residue and the initial soil pH. Our results show that 40–62% of the alkalinity of canola and chickpea residues resided in the soluble fraction. Furthermore, pH increases caused by soluble fractions may be transient if these contain large N concentrations. Soil properties that influence inorganic N dynamics such as inhibition of nitrification at acid pH will be important in determining the subsequent direction and magnitude of pH change.     

The effect of time of application and placement of sulphur fertilizer sources on yield of wheat,canola, and barley

Abstract

Most experiments with elemental S (So) have shown that spring application does not benefit annual crops, and it should be applied at least one year in advance so the prills are dispersed and oxidized to the sulphate (SO₄) state. Because preliminary work had indicated that placement of S prills appeared to affect prill dispersion and oxidation, a series of experiments were conducted to determine how placement and time of application affect yields of canola (Brassica napus L.), wheat (Triticum aestivum L.) and barley (Hordeum vulgare L.). Response of crops to S was variable and generally, similar for both So and SO₄ sources. Response to So was better when there was shallow incorporation of the prills in the spring by harrows before planting or the placement of the prills in a shallow band (2.5 cm depth) and then planting the seed with the hoe‐opener the next day in the same track of the fertilizer band. Elemental S increased the yield of wheat as much as 0.46 t/ha and canola, 0.99 t/ha. Prill dispersion was dependent on wetting and drying, weathering and physical dispersion with seeding implements. Because of the several factors that affect availability of S, general recommendations for use of S on annual crops should be made on the basis of regional testing.     

Soil pH decline in relation to rotation, tillage, stubble retention and nitrogen fertilizer in S.E. Australia

Abstract. The decline in topsoil (0–0.1 m) pH (CaCl₂) over 11 years (1979–90) was measured in a rotation, tillage, stubble and nitrogen fertilizer experiment on a Chromic Luvisol at Wagga Wagga in S.E. Australia. The rotations consisted of annual wheat cropping (WW) with and without nitrogen fertilizer (100 kg N/ha/year), alternating lupin-wheat (LW) and subterranean clover-wheat (CW). The initial mean pH at the site was 4.9 and the experiment was preceded by subterranean clover-based pasture for most of the previous 19 years. An initial rapid decline in soil pH under all treatments over the first 8–9 years was followed by a 2–3 year period when no further decline was detected. The annual rate of pH decline over the first 8–9 years varied from 0.06 for WW to 0.09 units for WW with added N fertilizer. Apparent steady-state for WW after 11 years was approximately 0.5 pH units higher than for WW with added N fertilizer. There was no difference between CW and LW in the rate of decline or in the apparent steady-state reached. Six years' stubble burning in a LW rotation promoted a slightly higher pH than where stubble was retained. However, there was no significant effect of tillage in either LW or CW rotations. By 1990 the addition of N fertilizer to WW had increased the concentration of exchangeable aluminium by 100% and of manganese by 24%. The inclusion of a legume in the rotation increased the concentration of aluminium but did not affect manganese. However, burning stubble in the LW rotation slightly decreased manganese concentrations.     

长期施钾和秸秆还田对河北潮土区作物产量和土壤钾素状况的影响

以河北冲积平原典型潮土区小麦-玉米轮作长期定位试验（19922009年）为基础,分析了长期施用钾肥和秸秆还田对作物产量、 土壤钾含量及钾素平衡的影响。研究结果表明,不同处理下小麦、 玉米17年平均产量均表现为NPKStNPKNPStNP,其中,小麦、 玉米NPKSt处理比NP处理分别增产9.37%和19.23%,NPK处理比NP处理分别增产6.32%和18.25%; NPSt处理比NP处理分别增产2.76%和9.60%; 长期定位施肥下,各处理耕层土壤（020 cm）各施钾肥的处理其速效钾、 缓效钾含量均与NP处理差异极显著,且表现为NPKStNPKNPStNP; 各处理下层土壤（2040 cm）的速效钾、 缓效钾含量差异均不显著,从钾素平衡看,NP处理钾素表观年盈亏量为-170.0 kg/hm2,土壤钾严重亏缺; NPSt处理实际平衡盈亏率-58.4%,表观年盈亏量为-150.6 kg/hm2; NPK处理钾素表观年盈亏量-3.1 kg/hm2,盈亏率-1.0%,基本接近平衡; NPKSt处理实际平衡盈亏率36.8%,表观年盈亏量为111.4 kg/hm2。试验结果说明,在潮土区,在施氮、 磷肥的基础上,配施钾肥或秸秆还田不仅能持续提高小麦、 玉米的高产、 稳产生产能力, 而且对保持农田土壤钾素平衡、 有效改善耕层土壤钾素状况、 提高土壤肥力有重要的作用。     

Improving organic C and N fractions in a sulfur-deficient soil with S fertilization

A field experiment was conducted over 9?years (1999 to 2007 growing seasons) in northeastern Saskatchewan on a S-deficient Gray Luvisol (Typic Haplocryalf) soil. The objective was to determine the relative effectiveness of N alone versus combined annual application of N (120?kg N?ha^?1) and S (15?kg S?ha^?1) fertilizers to a wheat–canola rotation on storage of total organic C (TOC) and N (TON) and on the light fraction organic C (LFOC) and N (LFON) in soil. Compared to N alone, annual applications of S fertilizer in spring in a combination with N resulted in an increase in soil of TOC (by 2.18?Mg C?ha^?1), TON (by 0.138?Mg N?ha^?1), LFOC (by 1,018?kg C?ha^?1), and LFON (by 42?kg N?ha^?1). The relative increases in organic C or N due to S fertilizer application were much higher for the light organic fractions (36.9% for LFOC and 27.5% for LFON) than for the total organic fractions (9.2% for TOC and 7.3% for TON). The findings demonstrate the importance of a balanced/combined application of N and S fertilizers to crops in storing more organic C and N in this S-deficient soil.     

华北平原冬小麦产量变异的气象影响因子分析

采用1988-2015年华北平原冬小麦种植区46个市的统计产量和相应46个气象站点的逐日气象资料,通过Logistic曲线和双曲线方法分离出气象产量,并构建气象产量与生长季主要气象因子的多元统计关系,以明确华北平原冬小麦产量变异的气象影响因子。结果表明：（1）1988-2015年华北平原冬小麦产量在3200～6800kg·hm-2,中部地区产量最高,南部地区产量的变异高于中部和北部地区。（2）生长季日照时数、温度和降水平均值的年际变化影响了17%～78%的气象产量的变异,其中54%的地区达到显著水平（P＜0.05）。影响程度较高的地区主要分布在河北南部、山东西部和河南的东北部地区。（3）播种-返青阶段的降水显著影响产量变异,降水量每增加1%,天津、驻马店及山东西北部等地产量将上升13～74kg·hm-2,而河北北部、河南南部、山东南部等地产量将下降16～80kg·hm-2。返青-成熟阶段对产量变异影响较大的因子为最低气温,平均最低气温每上升1-C,天津和石家庄、山东东部和西部及河南东部等地产量将增加50～295kg·hm-2,而北京、唐山和枣庄等地将减少76～124kg·hm-2。总体来看,温度对华北平原冬小麦产量变异影响范围更广且更加显著,但气象因子对产量变异的影响受局地品种和管理措施等影响呈现较大的空间差异。     

Energy balances and SOC and N stocks as affected by organic amendments and inorganic N fertilization in a semi-arid environment (IOSDV-Madrid)

A long-term field experiment (1984–2011), was conducted on a Calcic Haploxeralf from semi-arid central Spain to evaluate the combined effect of three treatments: farmyard manure (FYM), straw and control without organic amendments (WOA) and five increasing rates of mineral N on: (1) some energetic parameters of crop production, and (2) the effect of the different treatments on soil organic carbon (SOC) and total N stocks. Crop rotation included spring barley, wheat and sorghum. The energy balance variables considered were net energy produced (energy output minus energy input), the energy output/input ratio and energy productivity (crop yield per unit energy input). Results showed small differences between treatments. Total energy inputs varied from 9.86 GJ ha^?1 year^?1 (WOA) to 11.14 GJ ha^?1 year^?1 in the FYM system. For the three crops, total energy inputs increased with increasing rates of mineral N. Energy output was slightly lower in the WOA (33.40 GJ ha^?1 year^?1) than in the two organic systems (37.34 and 34.96 GJ ha^?1 year^?1 for FYM and straw respectively). Net energy followed a similar trend. At the end of the 27-year period, the stocks of SOC and total N had increased noticeably in the soil profile (0–30 cm) as a result of application of the two organic amendments. Most important SOC changes occurred in the FYM plots, with mean increases in the 0–10 cm depth, amounting an average of 9.9 Mg C ha^?1 (667 kg C ha^?1 year^?1). Increases in N stocks in the top layer were similar under FYM and straw and ranged from 0.94 to 1.55 Mg N ha^?1. By contrast, simultaneous addition of increasing rates of mineral N showed no significant effect on SOC and total N storage.     

A Four-Year Study on Influence of Biosolids/MSW Cocompost Application in Less Productive Soils In Alberta: Nutrient Dynamics

Composting municipal solid waste and biosolids and applying it on arable land have become an alternative way to treat waste in large municipalities in North America. However, cost of compost transportation and application constrains the compost use on the land further away from where it is produced. A four-year experiment was conducted (1998-2001) in less productive soils in Alberta to determine the effect of once in four year application of cocompost on soil nutrient dynamics and crop N uptakes. There were three crop blocks: barley (Hordeum vulgare L.), wheat (Triticum aestivum L), and canola (Brassica rapa), and they were rotated annually. The compost was only applied in 1998 at a rate of 50, 100 and 200 t/ha. Soil samples were taken in spring of every year after initial compost application to determine extractable N, P, K, S, Cu, Zn, Soil pH and EC. Each year, crops were harvested and N uptake was determined. Total concentrations of an array of heavy metals in the first year and fourth year after compost application were determined as well. The results showed that the release of N from the compost was high in the first year after compost application and then declined in each subsequent year. Similar to that release pattern was sulphur. The release of phosphorus from compost was steady throughout the four-year experimental time. Crop N uptake from compost application varied with crops and sites. The over all N use efficiency for three crops and two sites was 11%, 3%, 1% and 2% for the first and subsequent three years. The total heavy metal concentrations in the compost amended soils in the first and fourth year after compost application were similar, and they were below the standard of Canadian Fertilizer Act. Our results showed that N released from compost occurred mostly in the first two years after application, suggesting that an application frequency of once in every second year may be better than the once in every four year application strategy, especially with 100 t/ha application rate.     

The Effect of MSW Compost on Metal Uptake and Yield Of Wheat,Barley and Canola in Less Productive Farming Soils of Alberta

Experiments were started in May 1998 at two sites to measure various crop responses to a mixed municipal solid waste-biosolids cocompost (named Nutri Plus) and examine the fate of certain metals associated with Nutri Plus compost. There were six treatments: Check, 50, 100, and 200 T compost/ha, NPKS (75 kg nitrogen (N) /ha, 20 kg phosphorus (P)/ha, 45 kg potassium (K) and 18 kg sulphur (S)/ha), PK (20 kg P, 45 kg K/ha), and three crops: canola (Brassica rapa cv. ‘Hysyn 110’), wheat (Triticum aestivum L. cv. ‘Roblin’) and barley (Hordeum vulgare L. cv. ‘Lacombe’). Each treatment was replicated four times and was in a complete randomized block design. In the compost treatments, 20 kg P and 45 kg K were applied due to low concentration of these two nutrients in the compost. Soil and plant samples were analyzed for nutrient content such as N, P and K. In addition, plant samples and soil samples after the compost application were also analyzed for elemental content of As, B, Cr, Co, Cu, Zn Se, Mo, Cd, Hg and Pb. The research results show that the compost slightly increased heavy metal concentrations in the soil but did not cause any phytoxicity to crops. Yield from 100 and 200 T/ha application was higher with the compost than with NPKS treatment. However, the yield of the 50 T/ha application was similar to that of NPKS treatment. Comparing the two sites, the compost apparently was more beneficial at Site 1 than at Site 2 in the year of application. This is likely due to the lower indigenous soil fertility and poor soil physical properties at Site 1. The N content in cereal grains was similar among the compost treatments but lower than the Check and NPKS treatments due to the diluting effect of higher yield. The oil content in canola seed was similar among all treatments. The results suggest that Nutri Plus compost applications generated positive yield responses in all three crops. Crop yield increased as the application rate increased. Heavy metal loading was not an immediate problem with the compost application, although it will limit total compost application over time to the same soil     

荒漠绿洲区临泽小枣及枣农复合系统需水规律研究

在大田环境下,通过建造2m×2m×2m的封底观测池,利用水量平衡法,研究了甘肃省河西走廊中部黑河中游绿洲临泽小枣、春小麦、紫花苜蓿单作及临泽小枣/春小麦、临泽小枣/紫花苜蓿间作复合系统的需水规律。结果表明,内部绿洲和边缘绿洲的临泽小枣从根系开始活动到落叶的需水量分别为497.2mm和859.2mm,春小麦从播种到收获需水量分别为447.9mm和809.9mm,紫花苜蓿从返青到霜降需水量分别为583.7mm和945.7mm,临泽小枣/春小麦复合系统需水量分别为647.7mm和1009.7mm,临泽小枣/紫花苜蓿复合系统需水量分别为980.3mm和1342.3mm。边缘绿洲临泽小枣/春小麦复合系统增加的需水量为枣树需水量的17.5%,小麦需水量的24.7%;临泽小枣/紫花苜蓿复合系统增加的需水量为枣树需水量的56.2%,紫花苜蓿需水量的41.9%。内部绿洲临泽小枣春季(4月25日~5月31日)需水量为84.6mm,夏季(6月1日~8月31日)为351.3mm,秋季(9月1日~10月5日)为61.3mm;7月份需水强度最大,为4.8mm·d-1,6月份次之,为4.3mm·d-1,生长期平均需水强度为3.1mm·d-1。临泽小枣灌溉应保证4个关键水,即花前水、果实膨大水、丰果水和越冬水,灌水定额为1200m3·hm-2。     

Manure management practices applied to a seven‐course rotation on a sandy soil: effects on nitrate leaching

This experiment tested whether it was possible to incorporate broiler litter (BL) or cattle farmyard manure (FYM) into a 7‐yr arable rotation on a sandy soil without causing an increase in nitrate‐nitrogen (NO₃‐N) leaching. Four manure treatments (with adjusted fertilizer inputs), varying in frequency and timing of application, were imposed on the rotation and compared with a control that received inorganic fertilizer according to recommended rates. Over seven winters, the annual average NO₃‐N leached from the inorganic fertilizer treatment (control) was 39 kg/ha in 183 mm drainage. Total manure N loadings over the period of the experiment ranged between 557 and 1719 kg/ha (80–246 kg/ha/yr) for the four treatments. Three of the four manure treatments significantly increased NO₃‐N leaching over the rotation (P < 0.001). Annual applications of FYM (1719 kg/ha manure N or 246 kg/ha/yr) increased NO₃‐N leaching by 39%. We hypothesize that this was due to increased mineralization of the organic N accumulating from repeated FYM applications. BL applied each year (1526 kg/ha manure N or 218 kg N/ha/yr) increased NO₃‐N leaching by 52% above the control; BL applied 5 of 7 yr (972 kg/ha manure N or 139 kg N/ha/yr on average) and including inadvisable autumn applications increased leaching by 50%. BL applied in late winter or early spring every 2–3 yr (557 kg/ha manure N or 80 kg N/ha/yr on average) resulted in NO₃‐N leaching similar to the control. This suggests that to avoid additional NO₃‐N leaching from manure use in an arable rotation, manure should not be applied every year and autumn applications should be avoided; there are real challenges where manure is used on an annual basis.     

Rotation and tillage effects on available soil water for winter wheat in a semi-arid environment

The recent adoption of conservation farming systems in the semi-arid Canadian prairies opens up the possibility of replacing the traditional fallow period with non-cereal crops (oilseeds, legumes). However, information on changes to soil water regimes by inclusion of these crops, especially in combination with zero tillage, is sparse. A study was initiated in 1984 on a sandy clay loam soil at Lethbridge, Alberta, to investigate the performance of winter wheat (Triticum aestivum L.) under conventional, minimum and zero tillage in monoculture and in 2-year rotations with fallow, canola (Brassica campestris L.) or lentils (Lens culinaris Medic.)/flax (Linum usitatissimum L.). Conventional tillage in the Lethbridge region is shallow cultivation (10 cm) with a wide-blade (sweep) cultivator. Continuous cropping greatly depleted soil water reserves, resulting in some crop failures. Averaged over 10 years, available water for establishment of winter wheat in fall was least after canola (45 mm), followed by continuous winter wheat (59 mm), lentils/flax (74 mm) and fallow (137 mm). In this semi-arid region, the effect of rotation on soil water was much greater than that of tillage. Zero tillage had relatively little impact on available water to 1.5 m depth. However, once the experiment had been established for 6–7 years, available water in the 0–15 cm depth under winter wheat in spring was greatest under zero tillage. Precipitation storage efficiency during the fallow year was generally unaffected by tillage system.     

COMPARING FERTILIZER PHOSPHORUS REQUIREMENTS OF CANOLA,LUPIN, AND WHEAT

Increases in yield due to applications of phosphorus (P) (0, 5, 10, 15, 20, and 40 kg P/ha) applied as single (ordinary) superphosphate were measured for canola (Brassica napus), lupin (Lupinus angustifolius) and wheat (Triticum aestivum) in a field experiment on a deep sandy soil near Esperance, south-western Australia (WA). There are no data comparing the P requirements of these species grown at the same time, which was done by determining the amount of P required to produce 90% of the maximum yield for each species. The amount of P required was about 50% less for canola than wheat and about 10% more for lupin than wheat (60% more than canola). For each amount of P applied, the concentration of P in shoots and grain was greater for canola, followed by lupin and then wheat, suggesting that canola and lupin roots were better at accessing soil P than wheat. The critical concentration of P (diagnostic) required for 90% maximum yield of dried shoots measured in September was about 2.3 g/kg P for wheat, 2.8 g/kg P for lupin, and 3 g/kg P for canola. Similar critical values were obtained when P concentration in the shoots was related to grain yield (prognostic).     

Carbon input from 13C-labeled crops in four soil organic matter fractions

This study quantified the fate of new carbon (C) in four crop sequences (lentil–wheat, canola–wheat, pea–wheat, and continuous wheat). Lentil–wheat and continuous wheat were grown in intact soil cores from a Brown Chernozem (BCz) and canola–wheat, pea–wheat, and continuous wheat in cores from a Dark Brown Chernozem (DBCz). In the first growing cycle, plants were pulse-labeled with ¹³C-CO₂. Soil ¹³C pools were measured once after the labeled growing cycle to quantify root biomass contribution to soil organic matter (SOM) in a single cycle and again after a second growing cycle to quantify the fate of labeled root and shoot residues. ¹³C was quantified in four SOM fractions: very light (VLF), light (LF), heavy (HF), and water extractable organic matter (WEOM). For BCz lentil, BCz wheat, DBCz canola, DBCz pea, and DBCz wheat in the labeling year, root-derived C estimates were 838, 572, 512, 397, and 418 mg of C per kg soil, respectively. At the end of the second growing cycle, decreases in root-derived C were greater in the VLF, which lost 62 to 95 % of its labeled ¹³C, than the LF (lost 21 to 56 %) or HF (lost 20 to 47 %). Root-derived C in WEOM increased 38 to 319 %. On DBCz, even though wheat and pea produced less aboveground biomass than canola, they generated similar amounts of SOC by fraction indicating that their residues were more efficiently stabilized into the soil than canola residues. Combining ¹³C repeat-pulse labeling and SOM fractionation methods allowed new insights into C dynamics under different crop sequences and soil types. This combination of methods has great potential to improve our understanding of soil fertility and SOM stabilization.     

超高产栽培条件下冬小麦对磷的吸收、积累和分配

为明确超高产栽培条件下（9000 kg/hm2）冬小麦的磷素营养规律,为合理施肥提供研究依据,于20042006年冬小麦生长期间,通过田间取样,分器官测定磷素含量,研究了超高产冬小麦对磷的吸收、积累和分配特点。结果表明:在产量水平为9000 kg/hm2左右的条件下,不同品种各器官中的含磷量及全生育期中磷的总积累量存在一定差异,但一般不显著,显示出不同品种磷素营养特点的共性特征。地上部不同器官的含磷量（P2O5,下同）为0.25%～2.32%（干重）。不同生育时期含磷量最高的器官随生育进程逐渐更替,生育早期为叶鞘,中期为茎秆和穗,后期为籽粒。不同品种小麦各器官对磷的积累量,生育前期一般以叶片中最高,生育后期以籽粒中最高。小麦吸收的磷在孕穗期前主要分配在叶片中,多数品种在50%以上。成熟期磷在籽粒中的分配率最高,各品种均达到60%以上。在本研究的超高产栽培条件和产量水平下,冬小麦全生育期地上部器官中磷的最高积累量为110.8～151.4 kg/hm2,每生产100 kg籽粒吸收磷素1.25～1.66 kg。各品种对磷吸收量最高的阶段,一般都在起身到开花期之间,其次是在冬前的苗期。这表明,冬前和起身到开花期是冬小麦吸收磷的关键时期。根据上述磷的吸收积累特点,在确定施肥方案时,磷肥应以底肥为主,以促进小麦生长和对磷的吸收。     

Effects of Broad-Leaf Crop Frequency in Various Rotations on Nitrate Nitrogen and Extractable Phosphorus in a Black Chernozem Soil

In the Canadian prairies, current recommendations allow growing of canola or pea once every 4 years on a particular field to effectively mange diseases, insects, and weeds, but producers are interested in increasing frequency of these crops to optimize economic returns. A 4-year (from 1999 and 2002) field experiment, with treatments consisting of rotations of monoculture canola and pea to rotations that contained these crops every 2, 3, and 4 years with wheat and flax, was conducted on a Black Chernozem (Udic Boroll) silty clay at Melfort, Saskatchewan, to determine the impact of frequency of broad-leaf crops canola and pea in various crop rotations on accumulation and distribution of nitrate nitrogen (N) and extractable phosphorus (P) in the soil profile after 4 years. Two cultivars of canola, an herbicide-tolerant blackleg- resistant variety (hybrid) and a conventional (not herbicide tolerant) open-pollinated, blackleg-susceptible variety (OP), were included. Mean effects of crop rotation or rotation length on soil nitrate N were not significant, though the amount of soil nitrate N in different soil layers tended to be greatest with monocultures and least in the 4-year rotation with flax. Effects of crop phase (i.e., individual crops that make up the rotation)?×?crop rotation interactions on soil nitrate N were significant for all layers in the soil profile. The amounts of nitrate N in soil after canola, especially hybrid canola, were lowest in most crop rotations, suggesting the importance of canola in minimizing downward movement of nitrate N in the soil profile. Soil extractable P in the 0- to 15-cm layer was least with monocultures and greatest in the 4-year rotation with flax. There was a significant effect of crop phase on soil extractable P, but soil P levels varied with crop phase in different rotations. In conclusion, residual nitrate N in soil can be reduced by extending crop rotations and using high-yielding disease-resistant canola cultivars, most likely by improving crop yields.     

Comparison of the decomposition and N and P mineralization of canola, pea and wheat residues

Insight into nutrient cycling is gained by understanding the dynamics and quantifying nutrient mineralization from decomposing crop residues. Since wheat (Triticum aestivum L.), canola (Brassica napus L.) and pulse crops such as pea (Pisum sativum L.) are commonly grown in rotation, our objectives were to: (1) compare, using the mesh bag technique, the dry matter (DM) loss and release of N and P of straw and root residues of those crops in the 10-11 months following harvest, and (2) determine the influence of N fertilizer on residue decomposition and nutrient release. The no-tillage study started in autumn 1997 when straw residues were placed on the soil surface and root residues were buried in the soil, and sampled periodically through the 1998 growing season. Wheat was grown in 1998 and received 0 or 60 kg N ha^-1. The study was repeated in 1998/1999. Wheat straw decomposed more slowly than canola or pea straw (losing an average of 12%, 24% and 25%, respectively, of initial DM in 10-11 months), however, the converse was noted for root residues (42%, 26% and 19% of initial DM). Average net N mineralization from wheat, canola and pea straw was essentially 0, 0.7 and 5.6 kg N ha^-1, respectively. Phosphorus released from straw ranged from 0.5 kg ha^-1 for pea to 0.75 kg ha^-1 for canola. Net N and P mineralization from root varied little between crop species: 0.9-1.6 kg N ha^-1 and 0.1-0.3 kg P ha^-1. Nitrogen fertilization increased DM loss, and N and P release from straw residues.