Quality studies on wheat grown in different cropping systems: a holistic perspective

Spring wheat from a conventional (CONV) and an organic (ORG1) cropping system, both with animals, and from an organic system without animals (ORG2) was evaluated with respect to baking quality for the years 1995–2002. Amino acid (AA) composition was studied in both spring and winter wheat in 1993 and 2000–2002. The data were combined in multivariate analysis for exploration of the main factors responsible for the variation in quality. The most important factor for baking quality was weather conditions. High rainfall in May favoured baking quality in both cropping systems with animals, as did high temperature in May and high rainfall in July in the ORG1 system, and low rainfall in August in the CONV system. The only significant difference between the cropping systems was falling number, which was higher in ORG1 (252 s) than in CONV (205 s), probably due to a heavier CONV crop stand causing more difficult drying conditions. AA composition differed more between years than between cropping systems for both winter and spring wheat. The content of essential amino acids was high under the weather conditions associated with poor baking quality. The contents of threonine and leucine in spring wheat were significantly higher in ORG1, 1.76 and 8.11 g/100 g crude protein than in CONV, 1.63 and 7.72, respectively. In the interaction between AA and baking quality in spring wheat, it was possible to determine a correlation between phenylalanine, histidine, lysine and good baking properties. The primary effect was associated with weather conditions, but there was also an effect of differences between the cropping systems.     

Changes in N leaching and crop production as a result of measures to reduce N losses to water in a 6‐yr crop rotation

The effects of various measures introduced to increase nitrogen (N)‐use efficiency and reduce N losses to water in a 6‐yr crop rotation (winter wheat, spring barley, green manure, winter wheat, spring barley, spring oilseed rape) were examined with respect to N leaching, soil mineral N (SMN) accumulation and grain yield. An N‐use efficient system (NUE) with delayed tillage until late autumn and spring, direct drilling of winter wheat, earlier sowing of winter and spring crops and use of a catch crop in winter wheat was compared with a conventional system (CON) in a field experiment with six separately tile‐drained plots in south‐western Sweden during the period 1999–2011 (two crop rotation cycles). Total leaching of NO₃‐N from the NUE system was significantly 46 and 33% lower than in the CON system during the first and second crop rotation cycle, respectively, with the most pronounced differences apparently related to management strategies for winter wheat. Differences in NO₃‐N leaching largely reflected differences in SMN during autumn and winter. There was a tendency for lower yields in the NUE system, probably due to problems with couch grass. Overall, the measures for conserving N, when frequently used within a crop rotation, effectively reduced NO₃ concentrations in drainage water and NO₃‐N leaching losses, without severely affecting yield.     

Nitrogen Leaching Of Spring Wheat Genotypes (Triticum Aestivum L.) Varying In Nitrogen-Related Traits

Efficient use of nitrogen (N) by wheat crop and hence prevention of possible contamination of ground and surface waters by nitrates has aroused environmental concerns. The present study was conducted in drainage lysimeters for three years (1998–2000) to identify whether spring wheat genotypes (Triticum aestivum L.) that differ in N-related traits differ in N leaching and to relate parameters of N use efficiency (NUE) with parameters of N leaching. For this reason two spring wheat cultivars (‘Albis’ and ‘Toronit’) and an experimental line (‘L94491’) were grown under low (20 kg N ha^?1) and ample N supply (270 kg N ha^?1). The genotypes varied in parameters of NUE but not in N leaching. Grain yield of the high-protein line (‘L94491’) was, on average, 11% lower than that of ‘Toronit’ but among genotypes had significantly higher N in the grain (%), grain N yield, and N harvest index. Nitrogen lost through leaching was considerably low (0.42–0.52 g m^?2) mainly due to low volume of percolating water or the ability of the genotypes to efficiently exploit soil mineral N. There were no clear relationships between N-related genotype traits and N leaching, but across all treatments significantly negative correlations between volume of leachate and the amount of N in the total biomass and grain N yield existed.     

EUF-extrahierbarer Stickstoff und dessen Beziehung zu Stickstoffaufnahme und Ertrag von Weizen

EUF extractable nitrogen and its relation to nitrogen uptake and yield of wheat The investigations were focussed on the question whether nitrogen extracted from soils by EUF may reflect nitrogen availability for cereals. Soil samples were taken from the upper soil layer of farmers' fields differing in soil type and texture. Samples still taken in the autumn after the harvest of sugar beets as well as samples taken under cereals in January had relatively high contents of EUF extractable organic N and low contents of NO₃. Decrease in EUF extractable N during spring (March until end of May) under winter wheat was significantly correlated with the N uptake of the wheat and with grain yield. In the plots not treated with fertilizer N the organic N of the EUF-extracts was as a mineralizable N source more important for crop nutrition than the EUF extractable NO₃. The correlation between the EUF extractable N in spring and the grain yield of wheat was highly significant (r = 0.79***). In this correlation 20 different locations were implicated. Similar good correlations were found between the EUF extractable N and the N uptake of wheat.     

Yield and uptake of fertilizer nitrogen by direct-drilled winter barley growing on a chalk soil

Abstract. This paper reports the growth and yield of grain and the utilization of fertilizer nitrogen applied on either one or two occasions in spring to a crop of winter barley established by direct drilling on a chalk soil in southern England. Nitrogen, as ammonium nitrate, was applied at rates of 0 to 140 kg N ha⁻¹ in a range of proportions on two occasions (March and April 1981); nitrogen-15 was used to facilitate study of the nitrogen utilization by the crop.
When sampled before the second top-dressing in April, the greatest number of tillers were found on plants treated with 70 and 100 kg N ha⁻¹ in March. The total above ground dry matter production at harvest was greatest when the split nitrogen dressing totalled more than 100 kg N ha⁻¹, although the apparent efficiency of nitrogen usage (kg DM per kg N applied) was greatest when 60 kg N ha⁻¹ was divided equally between the two application dates. Grain yield was heaviest (6.471 ha⁻¹) at the largest rate of nitrogen applied (140 kg N ha⁻¹); the lightest yield from the nitrogen treated crops was recorded from 100 kg N ha⁻¹ applied as a single dressing in April that stimulated shoot production and decreased individual grain weight. The recovery in grain and straw of labelled fertilizer nitrogen applied only in March averaged 42.2% and was 49.8% when the nitrogen was applied only in April. The recovery of nitrogen applied in both March and April at the total rate of 100 kg N ha⁻¹ but split 30/70 or 70/30 was 44.5% and 42.5% respectively. Non-fertilizer sources of nitrogen contributed 60.7–71.7% of the total nitrogen uptake by the crop at harvest.     

Residual nitrogen effects on a succeeding oat (Avena sativa L.) Crop of clover species and ryegrass (Lolium perenne L.) undersown in winter wheat (Triticum aestivum L.)

The aim of the present investigation was to study the effect of white clover (var. Milka and Donna), red clover (var. Fanny) and ryegrass (var. Tove) undersown in winter wheat on a succeeding oat crop. Under the climatic conditions prevailing in Sweden, growing a catch crop after winter cereals is of particular interest because the latter are usually followed by a spring sown crop, leaving the ground bare during autumn and winter. Field trials were carried out during three growing seasons in an integrated farming system and for one year in an organic farming system. Competition from the dense wheat crop in the integrated farming system had a negative effect on the undersown species, and at harvest of the wheat they showed quite poor growth in all three years, with nitrogen contents under 5 kg ha^?1. No significant yield increase was measured without added nitrogen when the averages for all three years were calculated. On average, the grain yields were improved by 750 kg ha^?1 (14% moisture content) for the treatments with undersown clover for all three years when 90 kg N ha^?1 were added. The experiment within the organic system showed a different pattern with a better development of the undersown clover species, with nitrogen contents approximately 25 kg ha^?1 and an improvement in oat grain yield, from around 2?000 kg ha^?1 for the control to almost 3?500 kg ha^?1 with clover undersown the previous year.     

Animal manure slurries as a source of nitrogen for cereals; effect of application time on efficiency

Abstract. Field experiments undertaken at 14 sites, on a range of soil types, in lowland England, during the cropping years 1989–1993, tested the effectiveness of cattle or pig slurry as a source of nitrogen for cereal cropping. Slurry was applied in autumn, winter and spring, to autumn and spring sown cereal crops. Assessments included slurry nitrogen efficiency relative to N in spring applied fertilizer in terms of both grain yield and grain protein production, apparent crop recovery and content of mineral nitrogen in soil profiles. Crop response to nitrogen was poor at seven sites where high residues of soil mineral nitrogen (SMN) were present. On the seven responsive sites, spring slurry applications proved more efficient (mean 40%) as a source of N than autumn (mean 24%) or winter applications (mean 32%). These differences were smaller than reported in a number of other studies, probably as a result of relatively low excess winter rainfall, resulting in less nitrate leaching during the period of the investigation. Rapid incorporation into the topsoil of slurry applied in autumn, increased (28 kgN/ha) the SMN of samples taken early in the winter. However this increase did not lead to a consistent improvement in crop N uptake. Slurry dressings, whenever applied, can be expected to make a significant contribution to the N requirement of the succeeding crop and need to be taken into account when calculating the appropriate spring fertilizer application.     

高低畦种植模式下水氮耦合对冬小麦产量和水氮利用效率的影响

高低畦种植是在生产实践中摸索出的一套节水增产的冬小麦种植模式,尽管已被山东省列为农业主推技术,但由于建立时间尚短,其背后机理研究仍较薄弱,很大程度上制约了该模式的完善与推广应用。为探索高低畦冬小麦最佳的水氮管理制度,于2020—2022年开展田间试验,设置3个灌水定额(W1:120 mm、W2:90 mm、W3:60 mm)和3个施氮水平(N1:300 kg/hm²、N2:240 kg/hm²、N3:180 kg/hm²),以水氮充足的平作种植为对照(CK,灌水定额120 mm,施氮量300 kg/hm²),测定了不同生育期土壤含水率、成熟期地上部生物量和产量,并计算了麦田耗水量、水分利用效率、氮肥偏生产力和净利润等指标。结果表明：1)与平作种植相比,高低畦种植的麦田耗水量无明显差异,但冬小麦产量、水分利用效率、氮肥偏生产力和净利润分别提高14.8%～17.6%、15.9%～16.9%、14.8%～17.6%和58.9%～112.6%,说明高低畦种植模式具有增产与节水有机统一的良好潜力。2)灌水水平...     

Nitrogen balance in a soil‐wheat system under plow‐ and no‐tillage in the argentine humid pampa

Abstract

Changing conventional tillage to conservation tillage systems affects nitrogen (N) cycling in agroecosystems. Our objective was to evaluate the role of soil organic pools, specially plant residues, as sources‐sinks of nitrogen in an humid and warm temperate environment cropped to wheat, under plow‐ and no‐tillage. The experimental site was in the Argentine Pampa on a Typic Hapludoll. A balance‐sheet method was used: Nupt+Nres=Nsow+Nmin, where Nupt=N uptake by the crop at harvest; Nsow=soil mineral N as NH₄ and NO₃ at 0–90 cm depth, one month before sowing, plus N added as fertilizer; Nres=residual soil mineral N as NH₄ and NO₃ at 0–90 cm depth, at harvest; Nmin=N mineralized from humus and plant residues during wheat growing period. Nupt did not differ between tillage systems. Nitrogen supply by the mineral N pool, estimated by the difference Nsow‐Nres, was ca. 150 kg N ha^‐1 in both tillage systems. Plant residues decomposed and released N under both treatments. This organic N pool decreased 77% along the crop cycle. Nmin, calculated using the balance equation was 83 kg N ha^‐1, and did not differ between tillage managements, representing 35% of Nupt. This results highlight the importance of the organic pools as sources of N for wheat in the Humid Pampa. They also brink our attention on the importance for evaluate residue decomposition and humus mineralization in warm‐temperate regions when fertilizer requirements are determined, in order to minimize environmental hazard and economic losses by overfertilization.     

冬小麦上短控释期尿素的适宜施用量与施用方法研究

【目的】控释尿素受土壤温度、 水分等环境条件的影响,应用效果不一。对比相同施氮量下一次性基施控释尿素与尿素分期施用,以及控释尿素和普通尿素追施对冬小麦籽粒产量、 品质, 氮肥利用率及综合经济效益的影响,可为控释尿素的合理施用提供理论和技术依据。【方法】采用大田试验,选用新麦26为供试材料,随机区组试验设计,调查了冬小麦籽粒产量、 主要品质性状、 氮肥利用率及经济效益。设两个试验,试验1: 控释尿素和普通尿素各设5个氮肥水平,即N 0、 120、 160、 200和240 kg/hm2; 试验2: 设不施氮肥、 N 200 kg/hm2总氮量下普通尿素和控释尿素均40%返青期追施3个处理。【结果】 1)与不施氮(CK)相比,控释尿素和普通尿素均可显著提高小麦籽粒产量,且随着施氮量的增加而增加,其中以分期施用普通尿素N 240 kg/hm2处理籽粒产量最高。相同施氮量下,分期施用普通尿素处理小麦籽粒产量显著高于一次性基施控释尿素处理(N 160 kg/hm2除外)。然而,返青期追施控释尿素处理小麦籽粒产量显著高于同期追施普通尿素处理,增产率达15.8%; 2)相同施氮量下,分期施用普通尿素处理较一次性基施控释尿素处理的小麦籽粒容重、 蛋白质含量、 水分含量、 湿面筋含量均有所提高,且两种尿素处理间籽粒容重在N 160 kg/hm2和N 200 kg/hm2时差异达显著水平。然而,返青期追施控释尿素处理小麦籽粒容重、 湿面筋含量、 蛋白质含量等品质指标显著高于同期追施普通尿素处理; 3)两种尿素处理氮肥农学利用率和氮肥偏生产力随施氮量的增加而降低,在相同施氮量下分期施用普通尿素处理显著高于一次性基施控释尿素处理。此外,与分期施用普通尿素处理相比,一次性基施控释尿素处理减少了小麦拔节期追肥人工成本投入,但由于一次性基施控释尿素处理籽粒产量较低和氮肥价格较高,导致经济效益相对较低。然而,试验2结果表明,返青期追施控释尿素处理氮素利用率(氮肥农学效率、 氮肥偏生产力及氮素回收率)和经济效益显著高于同期追施普通尿素处理。【结论】本研究地区较适宜的推荐氮肥施用量为N 200 kg/hm2,一次性基施控释尿素较适宜于劳力欠缺的农户,而对于个别劳力充足的农户则适宜采用分期追施普通尿素或者小麦返青期追施控释尿素的氮肥管理技术。因此,在当前农村劳动力日益减少,用工成本日益增加以及种粮比较效益持续降低的大环境下,氮素肥料合理选择和施用技术要依据实际情况而定。     

Effect of nitrogen rate on plant nitrogen loss in winter wheat varieties 1

Gaseous nitrogen (N) loss from winter wheat (Triticum aestivum L.) plants has been identified, but has not been simultaneously evaluated for several genotypes grown under different N fertility. Two field experiments were initiated in 1993 and 1994 at the Agronomy Research Station in Stillwater and Perkins to estimate plant N loss from several cultivars as a function of N applied and to characterize nitrogen use efficiency (NUE). A total of five cultivars were evaluated at preplant N rates ranging from 30 to 180 kg·ha^‐1. Nitrogen loss was estimated as the difference between total forage N accumulated at anthesis and the total (grain + straw) N at harvest. Forage, grain, straw yield, N uptake, and N loss increased with increasing N applied at both Stillwater and Perkins. Significant differences were observed among varieties for yield, N uptake, N loss, and components of NUE in forage, grain, straw, and grain + straw. Estimates of N loss over this two‐year period ranged from 4.0 to 27.9 kg·ha^‐1 (7.7 to 59.4% of total forage N at anthesis). Most N losses occurred between anthesis and 14 days post‐anthesis. Avoiding excess N application would reduce N loss and increase NUE in winter wheat varieties. Varieties with high harvest index (grain yield/total biomass) and low forage yield had low plant N loss. Estimates of plant loss suggest N balance studies should consider this variable before assuming that unaccounted N was lost to leaching and denitrification.     

Untersuchungen zur Stickstoff-Immobilisation in mineralisch gedüngten Ackerböden aus Löß während der Vegetationszeit von Winter-Weizen

Experiments on nitrogen immobilization in minerally fertilized soils from loess during the growing season of winter wheat The nitrogen regime has been simulated during the growing period of winter wheat 1984/85 on a stagnigleyic cambisol using a simple, functional computer model. The model includes N mineralization from soil organic matter, transport of water and nitrate as well as growth of wheat and N uptake by the crop. Simulation starts at harvest of the previous crop. Simulated and measured N supply (soil mineral nitrogen plus N uptake by the plant) were in good agreement between september and december 1984. On this loess plot as well as on 10 other ones an over-estimation of mineral nitrogen in the soil up to 40 kg/ha was observed with beginning of december/january 1984/85 reflecting a seasonal trend. Experiments with ¹⁵N enriched Ca-nitrate 1984/85 on microplots of the same field point to a non-consideration of nitrogen immobilization. Fertilizer-N-immobilization amounted up to 35 kg/ha in the soil and to further 15 kg/ha in the straw material. The pool of fixed ammonium was of no importance with respect to the mobilization-immobilization-turn-over of fertilizer nitrogen. Experiments 1988/89 on microplots of a colluvial loess soil indicate a change of biomass nitrogen being responsible for the seasonal N-immobilization. An increase of biomass-N of about 30 kg/ha was observed under the growing wheat crop. An additional N-immobilization of nearly 40 kg/ha was observed with straw incorporation. A similar increase of microbial biomass nitrogen under winter wheat has been observed during the growing period 1987/88.     

15N Fertilizer recovery in different tillage–straw systems on a Vertisol in north‐west Mexico

Tillage and residue retention affect nitrogen (N) dynamics and nutrient losses and therefore nitrogen use efficiency (NUE) and crop fertilizer use, however, there is little information about residual fertilizer effects on the subsequent crop. Micro‐plots with ¹⁵N‐labelled urea were established in 2014/2015 on a long‐term experiment on a Vertisol in north‐west Mexico. N fertilizer recovery (NFR) and the effects of residual fertilizer N for summer maize (Zea mays L.) and the subsequent wheat (Triticum durum L.) crop were studied in three tillage–straw management practices (CTB: conventionally tilled beds; PB‐straw: permanent raised beds with residue retention; PB‐burn: permanent raised beds with residue burning). Fertilizer ¹⁵N recovery rates for maize grain across all treatments were low with an average of 11%, but after wheat harvest total recovered ¹⁵N (¹⁵N in maize and wheat straw and grain, residual soil ¹⁵N) was over 50% for the PB‐burn treatment. NFR was lowest in CTB after two cropping cycles (32%). Unaccounted N from applied fertilizer for the maize crop averaged 120 kg ¹⁵N ha^?1 after wheat harvest. However, more than 20% of labelled ¹⁵N was found in the 0–90 cm soil profile in both PB treatments after wheat harvest, which highlights the need for long‐term studies and continuous monitoring of the soil nutrient status to avoid over‐application of mineral N fertilizer.     

圆褐固氮菌对春小麦产量和氮肥利用效率的影响

利用盆栽和田间试验,探讨了圆褐固氮菌Azotobacter chroococcum beijerinckN45及用其研制的生物氮肥对春小麦产量和氮肥利用效率的影响,旨在为生物氮肥的研制及其与化学氮肥的最佳配比用量提供理论依据。结果表明,盆栽试验中供试菌株N45具有对春小麦的增产作用和对氮肥利用效率的促进作用。将其研制为生物氮肥后,其效果在田间得到了很好的再现,盆栽与田间试验均是与半量化学氮肥配施效果最佳,相比同量化肥处理分别提高春小麦秸秆产量12.70%和16.34%;籽粒产量15.31%和11.77%;氮素收获指数0.68%和0.13%;氮肥农学利用率30.37%和59.39%;氮素吸收利用率26.53%和88.66%;氮肥偏生产力15.27%和11.77%;氮肥生理利用率12.24%和35.24%,同时还能够提高秸秆和籽粒中全氮、全磷和全钾的累积量。     

Functional traits associated with nitrogen use efficiency in wheat

The association between functional traits and nitrogen use efficiency (NUE) was investigated to assist the breeding of nitrogen (N) use-efficient bread wheat (Triticum aestivum ssp. aestivum) varieties. This study combined results from a climate chamber experiment involving 41 spring wheat varieties and a field experiment involving six winter and six spring wheat varieties grown with and without the application of mineral N fertiliser. The climate chamber experiment was analysed by partial least squares (PLS) regression, with several predictors and NUE as response, to identify traits related to NUE. Specific hypotheses were then tested in the field experiment. The PLS indicated six traits of particular importance for overall NUE: leaf chlorophyll (SPAD value) of the top leaf at stem elongation, grains ear^?1, ears pot^?1, straw biomass pot^?1, days between emergence and anthesis, and days between emergence and completed senescence. In the field experiment, the SPAD value of flag leaves of winter wheat around anthesis was positively correlated with NUE and total grain N, at both N levels. Fast development was positively correlated with high NUE and N uptake efficiency in spring wheat. Early senescence of the flag leaf was positively correlated with grain N concentration and negatively correlated with grain-specific N efficiency in winter wheat at low N fertilisation levels. The results indicate that high SPAD value of the top leaf might be a candidate trait that could be used in wheat breeding for improved NUE, while genetic variation in senescence could possibly be used to tailor varieties for different end-use quality when grown at low N. More studies are needed to validate these findings in other environments and for other genotypes.     

Post-harvest residues of field pea/spring rye mixtures as a valuable source of biological nitrogen for winter triticale

ABSTRACT

The purpose of the work was to determine the effect of the post-harvest residue biomass of field pea, spring rye and their mixtures on mineral nitrogen content in the soil profile after the forecrop harvest, as well as the yield and quantity of nitrogen accumulated in winter triticale grain. An experiment was conducted to examine the following two factors: (I) forecrop – mixtures: field pea – pure stand 100%, spring rye – pure stand 100%, field pea 75%?+?spring rye 25%, field pea 50%?+?spring rye 50%, field pea 25%?+?spring rye 75%; (II) forecrop harvest date: field pea flowering stage, field pea green pod stage. The results revealed that the lowest mineral nitrogen content in after harvesting spring rye in the flat green pod phase in the soil layer 0–30?cm and 30–60?cm respectively 2.36 and 1.41?mg?kg^?1 soil. Also, mineral nitrogen content was low in the 0–30 and 30–60?cm soil layers following field pea/spring rye mixtures, in particular the mixture containing 25?+?75% of the respective components. Winter triticale cultivation after field pea/spring rye mixtures harvested at the stage of field pea flat green pod contributes to high grain yield.     

Comparisons among cultivars of wheat,hulless and hulled oats: Dry matter,N and P accumulation and partitioning as affected by N supply

A better understanding of the impact of fertilizer nitrogen (N) on biomass and N accumulation, and their partitioning into different plant components is needed to optimize crop yield and quality. A field experiment with spring wheat (Triticum aestivum), hulless (Avena nuda), and hulled (Avena sativa) oats was conducted for 3 years in Ottawa, ON, Canada, to determine the crop responses to N addition (0, 75, and 150 kg N ha^–1). Biomass, N, and phosphorus (P) accumulation and partitioning into different plant components were examined during the growth season. Lodging score was determined for all crops when it occurred and again at harvest. During the growth season, both hulless and hulled oats and the wheat cultivar showed almost similar patterns of N and P accumulation with maximum contents at late grain filling or at harvest. Plant N concentration was up to 60 g kg^–1 during the seedling stage, decreased gradually with advancing growth stages, and was lowest at harvest. Nitrogen treatments significantly increased plant N and P contents. At heading stage, N treatments enhanced dry matter (24%–45%), N (35%–135%), and P (27%–45%) contents in plant components (i.e., culm, leaf, and head), but also enhanced crop lodging, especially in oats. Both hulled and hulless oats had higher total plant N (5%–35%), N : P ratio, and dry‐matter content in leaf (6%–43%) and head (0%–129%) along with higher P (up to 27%) in culm than the wheat cultivar. The wheat cultivar accumulated greater dry matter and higher N content in kernels than both hulled and hulless oats at harvest. Both hulled and hulless oat cultivars exhibited similar lodging susceptibility to N addition (75 or 150 kg N ha^–1), produced lower dry weight and lower kernel N, and hence lower grain yield than the wheat cultivar. The larger vegetative dry‐matter accumulation at heading coupled with higher P content in culms under high‐N‐supply conditions may be related to severe lodging in oat cultivars.     

氮肥对节水栽培冬小麦产量、土壤硝态氮残留的影响

在节水栽培条件下，研究了不同施氮量及氮肥运筹对冬小麦产量、氮肥利用率及生育期间土壤硝态氮的时空变化特征。同时计算了成熟期土壤硝态氮残留量。结果表明。节水栽培条件下冬小麦产量对氮肥反应不明显。氮肥利用率则随施氮量增加而显著降低。同时氮肥用量的增加显著增加了成熟期土壤硝态氮残留量。不同生育期0～60cm土层硝态氮含量均随施氮量增加而增加，开花期表现为施氮量157．5kg／hm^2或226．5kg／hm^2时氮肥一次性底施处理硝态氮含量均低于分次施用处理，成熟期表现为施氮量157．5kg／hm^2时氮肥分次施用处理高于一次性底施处理，而施氮量226．5kg／hm^2则相反。由此可见，节水栽培条件下施氮量157．5kg／hm^2一次性底施既可满足冬小麦高产的要求，同时土壤硝态氮残留量较低。     

Alysimeter study of the effects of a ryegrass catch crop, during a winter wheat/maize rotation, on nitrate leaching and on the following crop

The effects of an intercrop catch crop (Italian ryegrass) on (i) the amounts and concentrations of nitrate leached during the autumn and winter intercrop period, and (ii) the following crop, were examined in a lysimeter experiment and compared with that from a bare fallow treatment. The catch crop was grown in a winter wheat/maize rotation, after harvest of the wheat, and incorporated into the soil before sowing the maize. A calcium and potassium nitrate fertilizer labelled with ¹⁵N (200 kg N ha^?1; 9.35 atom per cent excess) was applied to the winter wheat in spring. Total N uptake by the winter wheat was 154 kg ha^?1 and the recovery of fertilizer-derived N (labelled with ¹⁵N) was 60%. The catch crop (grown without further addition of N) yielded 3.8t ha^?1 herbage dry matter, containing 43 kg N ha^?1, of which 4.1 % was derived from the ¹⁵N-labelled fertilizer. Two-hundred kg unlabelled N ha^?1 was applied to the maize crop. During the intercrop period the nitrate concentration in water draining from the bare fallow lysimeters reached 68 mg N1^?1, with an average of 40 mg N1^?1. With the catch crop, it declined rapidly, from 41 mg N I^?1 to 0.25 mg N I^?1, at the end of ryegrass growth. Over this period, 110 kg N ha^?1 was leached under bare fallow, compared with 40 kg N ha^?1 under the catch crop. ¹⁵N-labelled nitrate was detected in the first drainage water collected in autumn, 5 months after the spring application. The quantity of fertilizer-N that was leached during this winter period was greater under bare fallow (18.7% of applied N) than when a catch crop was grown (7.1 %). In both treatments, labelled fertilizer-N contributed about 34% of the total N lost during this period. With the ryegrass catch crop incorporated at the time of seedbed preparation in spring, the subsequent maize grain-yield was lowered by an average of 13%. Total N-uptake by the maize sown following bare fallow was 224 kg N ha^?1, compared with 180 kg ha^?1 with prior incorporation of ryegrass; the corresponding values for uptake of residual labelled N were 3% (bare fallow) and 2% (ryegrass) of the initial application. Following the maize harvest, where ryegrass was incorporated, 22.7% of the previous year's labelled fertilizer addition was present in an organic form on the top 30 cm of lysimeter soil. This compares with 15.7% for the bare fallow intercropping treatment. Tracer analyses showed overall recoveries of labelled N of 91.7% for the winter wheat/ ryegrass/maize rotation and 97% for the winter wheat/bare fallow/maize rotation. The study clearly demonstrated the ecological importance of a catch crop in reducing N-leaching as well as its efficient use of fertilizer in the plant-soil system from this particular rotation. However, the fate of the organic N in the ploughed-down catch crop is uncertain and problems were encountered in establishing the next crop of maize.     

冬小麦对基肥和追肥15N的吸收与利用

【目的】 研究不同生育期 (花期、灌浆期和收获期) 肥料氮的去向和氮素的吸收运转对冬小麦产量形成的贡献。 【方法】 采用15N示踪结合盆栽试验,尿素N 90 mg/kg等分为基施和拔节期追施。分别在开花期、灌浆期和收获期破坏性取样,测定冬小麦地上部、根和土壤15N含量等指标。 【结果】 在整个生育期,冬小麦吸氮量42.8%来自土壤,57.2%来自肥料,其中来自基肥和追肥的比例分别为26.6% 和30.6%。冬小麦植株对氮肥15N 的吸收率随作物的生长而增加,从开花期到收获期增加了50%,15N氮肥在土壤中的残留率从开花期到收获期下降约50%。冬小麦收获后,约28.6%的肥料15N残留在土壤中,肥料15N损失率为33.9%,基肥氮的损失率比追肥氮高21%。冬小麦对肥料15N的全部回收率为37.5%,其中籽粒吸收量约是秸秆的4倍,64.9%的籽粒氮素从开花前营养器官吸收转运而来。 【结论】 在整个生育期,冬小麦吸收的氮素来源于肥料和土壤氮的比例约为6∶4,基肥和追肥氮对冬小麦氮素吸收具有同等贡献,在当前N 250 kg/hm2的施氮水平下,适当增加追肥氮的比例可以减少氮肥损失率。残留在土壤中的肥料氮对于补充土壤氮素消耗具有重要意义。