Field observations on nitrogen catch crops

Nitrogen catch crops help to reduce the loss of nitrogen from arable cropping systems during autumn and winter. The ability of catch crops to absorb nitrogen from the soil profile is affected by rate and depth of colonization of the soil by roots. The aim of the current work was to analyze total root length and root length density of catch crops in relation to above ground growth, nitrogen supply and crop species. In two field experiments roots were sampled with an auger. Experimental factors included crop species (winter rye, Secale cereale and forage rape, Brassica napus ssp. oleifera (Metzg.) Sinsk., or oil radish, Raphanus sativus spp. oleiferus (DC.) Metzg.), two sowing dates S1 and S2 (end of August and three weeks later) and two nitrogen treatments: N0, no nitrogen applied, and N1, nitrogen applied at non-limiting rate.The natural logarithm of the total root length, measured in the top 40 cm, L_0–40 (km m^-2), was linearly related to natural logarithm of the dry weight of the shoot, W (g m^-2). There was no effect of species or sowing date on this relation. For a given W, N1 treatments showed lower values of L_0–40 than N0 treatments. The decline in root length density, D (cm cm^-3), with depth, X (cm), was described with the function ln D = ln D₀ – qX, where D₀ is the value of D at zero depth and q the linear coefficient. D₀ was linearly related to L_0–40, without effect of species, time of observation or N supply. The ratio D₀/q, an estimate of the absolute root length, was 1.24 × L_0–40.Together the relations enable estimates to be made of total root length and of root length distribution with depth using shoot dry weight of catch crops and its change with time as input. The generation of such estimates of root distribution is necessary for model studies in which the efficacy of catch crops to prevent N losses is evaluated in relation to sowing dates, distribution of N in the soil profile and the distribution of rainfall in the season.     

Field observations on nitrogen catch crops. III. Transfer of nitrogen to the succeeding main crop

In temperate climates with a precipitation surplus during autumn and winter, nitrogen (N) catch crops can help to reduce nitrogen losses from cropping systems by absorbing nitrogen from the soil and transfer it to a following main crop. In two field experiments the catch crop species winter rye (Secale cereale) and forage rape (Brassica napus ssp. oleifera (Metzg.) Sinsk) or oil radish (Raphanus sativus spp. oleiferus (DC.) Metzg.) were planted end of August and 3 weeks later with a non-limiting supply of N and zero-N controls. In the next spring catch crops were incorporated into the soil. In Expt 1, N transfer was measured as (i) the N uptake of a potato test crop, grown with zero and 12.5 g m^–2 N applied, and (ii) the increase in soil mineral N (0–30 cm) in uncropped soil covered with polythene film. In Expt 2, N transfer was measured as the increase in soil mineral N in covered cylinders placed in uncropped soil (in situ incubation). Subsidiary laboratory incubations were performed in Expt 2. In Expt 1, the apparent recovery in potato of fertilizer N (R _f) was 0.56. The recovery in potato of N mineralized from 'native' N pools other than catch crop material (R _n) ranged from 0.43 to 0.51, depending on the value assumed for the depth of N extraction by potato roots. The average recovery in potato of incorporated catch crop N (R _c) was 0.34. Expressed as `fertilizer N replacement factor' (F _r) the latter was 0.61 (i.e. 1 kg of N in catch crop material counts for 0.61 kg fertilizer N). Under the film in Expt 1 the fraction net mineralization of incorporated catch crop N (M _n) was 0.36 on August 11 and 0.43 on October 18. In Expt 2, the average value of M _n was 0.31, which was lower than in Expt 1 and probably associated with the drier soil in Expt 2. In the laboratory incubations (20°C) M _n showed values up to 0.54 after 84 days with the largest rates of change in mineralization occuring early after the start of the incubation. In conjunction with literature data it is concluded that cultivation of nitrogen catch crops shows promise as a means to reduce N input and N losses in temperate climates with wet winters.     

油菜地上部干物质分配与产量形成模拟模型

利用油菜器官生长与发育进程及环境因子之间的定量关系,构建了基于分配指数的油菜地上部器官干物质分配动态模拟模型.各器官干物质分配指数随着生理发育时间而变化,基因型、播期、氮素及水分水平影响各器官干物质在地上部分配的大小.其中,氮素营养水平对绿色叶片干物质分配影响最大,氮素营养水平越高,绿色叶片分配指数越大;播期影响角果分配指数,晚播的角果分配指数高于早播.模型引入氮素营养指数、水分及播期影响因子来定量油菜各器官在实际生产条件下的分配强度,同时考虑了品种遗传特性的影响.通过不同品种氮肥处理试验建立模型,利用不同品种播期试验资料对模型进行了初步检验,表明模型具有较好的预测性和适用性.     

Influence of sowing windows and genotypes on growth,radiation interception,conversion efficiency and yield of guar

Crop growth largely depends on radiation. Radiation is the main impetus for photosynthesis and movement of photosynthates from source to sink. Therefore, identification of the optimum sowing windows and suitable cultivars for efficient utilization of radiation is of prime importance. A field study was conducted in red clay soil during 2014 and 2015 Kharif season and the treatments consisted of three genotypes and three sowing windows by using randomized complete block design with three replications. The effect of genotypes and sowing windows was found significant with respect to number of trifoliate leaves, leaf area ratio, dry matter production, grain numbers, pod length, test weight, grain yield, and stover yield of guar during 2014 as compared to 2015 sown crop. Statistically significant plant height, number of trifoliate leaves, number of branches, leaf area ratio, absolute growth rate, leaf area index, dry matter, grain number, pod length, grain yield, stover yield and a higher cumulative radiation interception were recorded with 15th August sown crop as compared to other sowing windows. The plant height, number of trifoliate leaves, number of branches, leaf area ratio, absolute growth rate, leaf area index, dry matter, grain number, pod length, grain yield, stover yield and maximum cumulative interception of radiation were significant with RGC-1003 as compared to RGC-936 and HG-365. It is observed that the incident PAR to dry matter accumulation conversion efficiency was varied with cultivars and different sowing windows which ranges from 0.74 g MJ⁻¹ to 0.79 g MJ⁻¹.     

Modelling and measuring the effect of nitrogen catch crops on the nitrogen supply for succeeding crops

Nitrogen catch crops are grown to absorb nitrogen from the rooting zone during autumn and winter. The uptake of N (N_upt) from the soil inorganic N pool (N_min) to a pool of catch crop nitrogen, will protect the nitrogen against leaching. After incorporation, a fraction (m) of the catch crop nitrogen is mineralized and becomes available again. However, not all available nitrogen present in the soil in the autumn is lost by leaching during winter. A fraction (r) of the nitrogen absorbed by the catch crop would, without a catch crop, have been retained within the rooting zone. The first year nitrogen beneficial effect (N_eff) of a catch crop may then be expressed b N _eff = m*N _upt - r* N _upt The soil-plant simulation model DAISY was evaluated for its ability to simulate the effects of catch crops on spring N_min and N_eff. Based on incubation studies, parameter values were assigned to a number of catch crop materials, and these parameter values were then used to simulate spring Nmin. The model was able to predict much of the vairiation in the measured spring Nmin (r² = 0.48***) and there was good agreement between the measured and the simulated effect of winter precipitation on spring N_min and Neff.Scenarios including variable soil and climate conditions, and variable root depth of the succeeding crop were simulated. It is illustrated that the effect of catch crops on nitrogen availability for the succeeding crop depends strongly on the rooting depth of the succeeding crop. If the succeeding crop is deep rooted and the leaching intensity is low, there is a high risk that a catch crop will have a negative effect on nitrogen availability. The simulations showed that the strategy for the growing of catch crops should be adapted to the actual situation, especially to the expected leaching intensity and to the rooting depth of the succeeding crop.     

Solar radiation interception by leafless, semi-leafless and leafed peas (Pisum sativum) under contrasting field conditions

Foliage composition, photosynthetic area index (PAI) and radiation interception were measured for crop canopies of leafless (var. Filby), semi-leafless (var. BS3) and leafed (var. Birte) peas (Pisum sativum). Tendrils and petioles contributed more than 60% of total leaf area for leafless peas but less than 30% for semileafless and leafed pea canopies. PAI was related to radiation interception by calculating attenuation coefficients which indicated that leafless peas intercepted more radiation per unit PAI than either semi-leafless or leafed peas. Data interpretation, however, was complicated because of difficulties in estimating the tendril and petiole surface area contribution to PAI. Radiation interception was related to dry matter accumulation by calculating photosynthetic efficiencies. Leafless and semi-leafless peas converted intercepted radiation into dry matter as efficiently as leafed peas. Under conditions of moisture stress, leafed and leafless peas both intercepted radiation more effectively but converted it into dry matter with reduced photosynthetic efficiency.     

Effect of soil compaction on growth, yield and light interception of selected crops

The response of spring barley (Hordeum vulgare, cvs Carnival and Atem), faba beans (Vicia faba, cv. Maris Bead), sugar beet (Beta vulgaris, cv. Monoire), forage maize (Zea mays, cv. Leader), forage peas (Pisum sativum, cv. Poneka) and white turnip (Brassica campestris, cv. Barkant) to topsoil compaction was investigated in a three year trial. Soil compaction was induced by tractor wheeling after crop sowing. Compaction reduced leaf area and dry matter accumulation in all crops in every season. Yield of barley was reduced by 29%, 27% and 40% in 1984, 1986 and 1987 respectively. Yield of maize, peas and turnip decreased by 33%, 14% and 13% in 1986 and 25%, 16% and 19% in 1987. Yields of beans and sugar beet were decreased by 34% and 35% respectively in 1984. Light interception was decreased in all crops in all three years of study but, with the exception of maize in 1987, the efficiency of conversion of radiant energy to dry matter was not significantly affected by soil compaction. It is concluded that reduced dry matter production and yield due to soil compaction was more a consequence of reduced light interception because of restricted leaf area development rather than as a result of an impaired ability of crops to utilise intercepted radiant energy.     

氮肥运筹对晚播冬小麦氮素和干物质积累与转运的影响

氮素平衡对干物质积累与分配的影响是农业生态系统研究的重要内容,在保障产量前提下减少氮肥施用量可减少环境污染与温室气体排放。以晚播冬小麦为研究对象,设置4个施氮量水平:0 kg/hm2(N0)、168.75 kg/hm2(N1)、225 kg/hm2(N2)、281.25 kg/hm2(N3),每个施氮量水平下设置2个追氮时期处理:拔节期(S1)、拔节期+开花期(S2),研究了氮肥运筹对晚播冬小麦氮素和干物质积累与转运及氮肥利用率的影响。结果表明:拔节期追施氮肥(S1)条件下,在225 kg/hm2(N2)基础上增施25%氮肥(N3)对开花期氮素积累总量和营养器官氮素转运量无显著影响;拔节期+开花期追施氮肥(S2)条件下,随施氮量增加,开花期氮素积累总量和花后营养器官氮素转运量升高;S2较S1显著提高成熟期籽粒及营养器官氮素积累量、花后籽粒氮素积累量及其对籽粒氮素积累的贡献率。同一施氮量条件下,S2较S1提高了成熟期的干物质积累量、开花至成熟阶段干物质积累强度和花后籽粒干物质积累量。同一追氮时期条件下,籽粒产量N2与N3无显著差异,氮肥偏生产力随施氮量增加而降低;同一施氮量条件下,S2较S1提高了晚播冬小麦的籽粒产量和氮肥吸收利用率。拔节期+开花期追施氮肥,总施氮量225kg/hm2为有利于实现晚播冬小麦高产和高效的最优氮肥运筹模式。     

分期施氮与CO2浓度升高对小麦光合及其物质积累和产量的互作效应

采用开顶式气室和盆栽方法,以冬小麦品种‘小偃22’为材料,探讨了分期施氮与CO2浓度升高对小麦抽穗期和灌浆中期旗叶光合、地上部物质积累和产量的互作效应.结果显示:(1)不施氮条件下CO2浓度升高对小麦旗叶叶绿素含量(SPAD)和可溶性蛋白含量、光合能力、地上部花后干物质和氮素累积量、籽粒产量的影响不明显(P>0.05)或产生显著负效应;在施氮(300mg/kg土)条件下各指标均不同程度增加,且大多数达到显著水平.(2)与氮肥全部基施相比,分期施氮时CO2浓度升高使灌浆期旗叶光合能力、地上部花后干物质和氮素累积以及产量增加的幅度较大,其中以播前、返青期和孕穗期施氮比例为5∶3∶2时最明显.研究表明,适当分期施氮可能更有利于发挥CO2浓度升高对冬小麦的增产作用.     

Biomass yield and nitrogen fixation of legumes monocropped and intercropped with rye and rotation effects on a subsequent maize crop

The research is focused on an ecologically sound and highly productive cultivation system for fodder and/or biomass for thermal power generation on the basis of winter legumes and maize as subsequent summer crop, managed without additional nitrogen fertiliser. Therefore the yield of biomass and N-fixing capacity of a winter pea (Pisum sativum L.) and crimson clover (Trifolium incarnatum L.) monocropped and intercropped with rye (Secale cereale L.) were examined for five years in a field trial. In mid-June above-ground biomass of winter crops was removed and maize transplanted. The winter crops achieved maximum dry matter yield about three to five weeks before maturity. Mixed stands yielded more biomass than pure stands and exhibited greater yield stability. The relative advantage of intercropping, expressed as land equivalent ratio (LER), determined for intercropped winter pea/rye were 1.1 to 1.2 and for crimson clover/rye 1.3. At maturity, the amount of fixed nitrogen ranged between 178 kg N for crimson clover and 242 kg N ha^-1 for winter pea, respectively. At the end of anthesis (middle of June, harvesting stage for silage fodder) 75% and 88% of the total fixed nitrogen was achieved, for clover and pea, respectively. In intercropping the amount of fixed nitrogen was lower than in pure stands due to a lower seed density of the legume; however, the N-fixing efficiency was greater than in pure stands. N-release of the winter pea in a pure stand produced a maximum yield in maize (Zea mays L.) without additional N-fertiliser. An additional N mineral fertilisation of 75 to 150 kg N and 75 to 225 kg N was necessary to achieve maximum yields in maize following intercropped winter pea and crimson clover, respectively. Legumes in mixed stands with rye resulted in lower amounts of residual nitrogen after maize harvest. The beneficial effect of legumes on maize can be divided into N-effects and rotation effects. Both effects were positive regarding winter pea. The rotation effect of crimson clover in pure stands on maize was negative. Allelopathic effects and the high sensitivity of crimson clover to mineral nitrogen in the soil, released by residues of the preceding crop, winter rape (Brassica rapa L.), were discussed as the reason for this observation. The combination of the winter pea in pure stand and maize achieved the highest total biomass yield from winter and summer crops, unfertilised (156 dt ha^-1 dry). The combinations of intercropped legumes and maize produced biomass yields of 142 to 145 dt ha^-1. Because winter pea is highly susceptible to lodging, intercropping with low seed density of rye is recommended (3/4 winter pea, 1/4 rye). The rye crop prevents lodging by providing support and high rates of N-fixation are achieved with high seed density of pea. Intercropping with crimson clover and rye should be based on high seed densities of legumes, too because rye is highly competitive within those mixtures. This revised version was published online in August 2006 with corrections to the Cover Date.     

Warming impacts on the dry matter accumulation,and translocation and nitrogen uptake and utilization of winter wheat on the Qinghai-Xizang Plateau

Aims Global warming is expected to be the strongest in high altitude mountainous areas, which are more ecologically fragile and economically marginalized. The Qinghai-Xizang Plateau is among such areas most vulnerable to global warming, and more than 80% of its population depends on subsistence agriculture. The aim of this study is to understand the impacts of warming on indigenous crop production, which can help to devise better strategies for crop adaptation and food security in this area.Methods A field warming experiment using a facility of free air temperature increase was conducted to simulate the predicted warming level in Caigongtang town, Lhasa City, China. The experiment consisting of two treatments (warmed and non-warmed) was performed using a completely random design with three replicates. An infrared heater (180 cm in length and 20 cm in width) of 1 500 W was suspended 1.5 m above the ground in each warmed plot. In each non-warmed plot, a ‘dummy’ heater of same dimensions was also suspended to mimic the shading effects. The warming treatment was performed from the sown date to the harvest date. We measured dry matter and nitrogen accumulation, partition and translocation of winter wheat (Triticum aestivum) using ‘Shandong 6’ under warming and control treatments.Important findings Results showed that, with 1.1 °C increase in daily mean air temperature during winter wheat growing season, the dry matter accumulation rate at population level from sowing to anthesis stage, grain dry matter partition ratio and contribution of dry matter translocation amount to grain after anthesis were 27.5%, 5.6% and 68.6% higher, respectively, in the warmed plots than those in the non-warmed plots. Meanwhile, warming increased nitrogen accumulation rate at population level of winter wheat. Nitrogen distribution proportions in grain and nitrogen translocation efficiency from vegetative organs to grain after anthesis in the warmed treatment were 6.0% and 5.5% higher than those in the non-warmed treatment, respectively. Compared with non-warmed treatment, warming decreased harvest index by 3.1%, though the difference was not statistically significant. Grain yield, nitrogen uptake efficiency, nitrogen partial factor productivity and nitrogen harvest index were 8.1%, 20.8%, 8.1% and 6.0% higher, respectively, in the warmed plots than those in the non-warmed plots. In conclusion, an increase in daily mean air temperature of about 1.1 °C can enhance plant growth during the pre-anthesis phase by mitigating the low temperature limitation, and accelerate dry matter and nitrogen partition and translocation to the grain after anthesis in winter wheat. These results suggest that warming may benefit winter wheat production through increasing nitrogen use efficiency in high altitude areas.     

水分亏缺和施氮对冬小麦生长及氮素吸收的影响

利用管栽试验研究了不同生育期,水分亏缺和施氮对冬小麦生长及氮素吸收的影响.结果表明：任何生育期水分亏缺都会影响冬小麦的株高、叶面积、干物质累积及对氮素的吸收.冬小麦对水分亏缺的敏感期为拔节期,其次为开花期、灌浆期和苗期.苗期干旱后复水对后期生长有显著的补偿效应,开花期适度干旱后复水对生物量形成和氮素吸收有一定的补偿作用,拔节期干旱对小麦的生长影响明显.相同氮肥处理下, 与不亏水处理比较, 苗期水分亏缺、拔节期水分亏缺、开花期水分亏缺、灌浆期水分亏缺的根系氮素积累量分别平均降低25.82%、55.68%、46.14%和16.34%,地上部氮素积累量分别平均降低33.37%、51.71%、27.01%和2.60%.在相同水分处理下冬小麦含氮量、累积吸收氮量都表现为高氮处理（0.3 g N·kg^-1FM）>中氮处理（0.2 g N·kg^-1FM）>低氮处理（0.1 g N·kg^-1FM）.水分逆境条件下施用氮肥对冬小麦植株生长和干物质累积及氮吸收具有明显的调节效应.     

氮肥后移对抽穗后水分胁迫下冬小麦光合特性及产量的影响

采用子母桶栽土培法模拟冬小麦抽穗后不同的水分胁迫状态,研究了氮肥后移对冬小麦光合特性及产量的影响.设置3个氮肥处理,分别为N₁(基肥∶拔节肥∶开花肥=10∶0∶0)、N₂(6∶4∶0)和N₃(4∶3∶3),模拟冬小麦抽穗后2种水分胁迫(渍水胁迫、干旱胁迫),设正常供水为对照.结果表明：相同供水条件下,N₂和N₃处理较N₁处理显著提高冬小麦灌浆期旗叶的SPAD和光合速率,确保了收获时较高的穗数、穗粒数和地上部分生物量;氮肥后移处理显著提高了冬小麦的耗水量,但其籽粒产量和水分利用效率也显著提高.相同氮肥条件下,干旱胁迫和渍水胁迫处理较正常供水显著降低了冬小麦开花期和灌浆期旗叶的光合速率、千粒重、穗粒数和产量.与正常供水相比,各氮肥条件下干旱胁迫和渍水胁迫处理花后旗叶光合速率及籽粒产量的减小幅度均表现为N₁＞N₂＞N₃.表明氮肥后移通过提高旗叶SPAD、减缓花后旗叶光合速率的下降幅度、增加地上部分干物质积累量,调控产量及其构成要素,以减轻逆境灾害(干旱和渍水胁迫)对产量的影响.     

江汉平原不同氮肥运筹模式下豆麦和稻/麦轮作系统小麦产量和经济效益差异

研究江汉平原豆麦(大豆/小麦)和稻麦(水稻/小麦)轮作系统中冬小麦生长规律对氮肥运筹模式的响应,可为缩小两种轮作模式下的小麦产量差异提供理论依据。试验设置传统施肥(70%底肥,30%越冬期追肥)和优化施肥(1/3底肥,1/3越冬期追肥,1/3拔节期追肥)2个处理,并以不施氮处理为对照,分析了豆麦和稻麦轮作系统中冬小麦的生长规律、产量及产量构成因素、肥料利用率和施肥效益等。结果表明: 施氮和轮作模式均对小麦产量有显著影响,优化施肥产量显著高于传统施肥,两者产量差异在豆麦轮作系统下为920 kg·hm^-2,在稻麦轮作系统下为2195 kg·hm^-2。相同轮作模式下,传统施肥冬季、春季群体茎蘖数高于优化施肥,而优化施肥在整个生育期干物质总积累量较传统施肥高5%~31%(豆麦)和14%~28%(稻麦)。传统施肥下豆茬小麦产量较高的原因是穗数、成穗率、群体干物质积累量等均高于稻茬小麦;优化施肥下稻茬小麦产量较豆茬小麦增加幅度更大,表明优化氮肥模式可缩小豆麦与稻麦轮作中小麦的产量差异。两种轮作模式中小麦花后粒重分别呈现“慢-快-中”(豆麦)和“中-快-慢”(稻麦)的增加趋势;氮肥农学效率、小麦季纯收益等指标均以稻麦轮作优化施肥处理最高。综上,在江汉平原地区,稻麦轮作优化施肥处理下小麦群体结构合理,干物质积累量较高,产量和施肥效益增加显著,是江汉平原地区兼顾产量与施肥效益的最佳模式。     

Effects of temperature on the development and growth of winter wheat roots

Winter wheat was sown on 2 dates with 3 levels of nitrogen fiertiliser (0, 50 and 200 kg N ha⁻¹) in one year and on 2 sites in a followign season. Shoot and root development and growth were measured between emergence and anthesis in the first season and emergence and 7 mainstem leaves in the second. Differences in temperature and light regime led to significant differences in shoot and root development and growth between sowing dates. A thermal time-scale, based on soil surface or air temperatures, with a base of 0°C, adequately described the production of mainstem leaves and nodal root axes over all treatments. Autumn applied nitrogen had little effect on development. Shoot growth and green area index increased exponentially with thermal time prior to spring nitrogen application and the completion of canopy development. Early-sown crops had larger root systems than late-sown crops prior to winter and this divergence was retained until anthesis. The relationship between root growth and thermal time was little better than with days after sowing and was not improved by either varying the site of temperature measurement or the base temperature used for calculation. Differences in soil texture and drainage, between sites, led to significant changes in root length distribution. Although spring applied nitrogen generally increased root length, its effects were inconsistent. There was a curvilinear relation between root length and the amount of photosynthetically active radiation (PAR) intercepted; this relation was unaffected by sowing date or nitrogen treatment. The amount of root produced per unit PAR decreased as the season progressed, reflecting the decrease in the proportion of total dry matter partitioned to the root system.     

The potential of hemp (Cannabis sativa L.) for sustainable fibre production: a crop physiological appraisal

Hemp (Cannabis sativa L.) fibre can be used as a raw material for paper and textile production. A comprehensive research programme in the Netherlands has concluded that fibre hemp is a potentially profitable crop, having the right profile to fit into sustainable farming systems. This paper presents an appraisal of the crop physiological characteristics and the agronomic potential of hemp. Parameter values of basic crop physiological characteristics such as light interception potential, radiation use efficiency and dry matter partitioning coefficients are given. The effect of crop management decisions such as cultivar choice, sowing date, plant density, and harvest date on the value of these parameters is discussed. A simple crop growth model was used to assess the yield potential of hemp for the climate of the Netherlands. Calculations made for a non-stressed late-flowering hemp crop sown on 15 April and harvested on 15 September give a stem dry matter yield of 17.1 t ha^-1. The effects of advancing or delaying sowing or harvest date on stem yield were calculated. Crop physiological characteristics of hemp are compared to those of kenaf (Hibiscus cannabinus L.). Radiation use efficiency and dry matter partitioning coefficients of the two crops are similar. Base temperatures for development and growth are lower in hemp than in kenaf. In a temperate climate with cool springs, canopy establishment will be more rapid in hemp than in kenaf. Hemp seems an excellent candidate to fill the niche for an annual fibre crop in a temperate climate.     

不同播期冬小麦氮素出籽效率与氮素利用及转运的相关性

为探讨不同播期冬小麦氮素出籽效率与氮素利用及转运的关系,在2014—2016年2个生长季,比较了不同播期(S₁:9月24日;S₂:10月1日;S₃:10月8日;S₄:10月15日;S₅:10月22日)冬小麦氮素出籽效率、氮素利用和转运的差异及相互间的关系.结果表明: 籽粒产量和单位面积粒数在不同播期处理间未发生显著差异.推迟播期降低了地上部氮素积累量和穗部氮素积累量,从而降低了氮素吸收效率,但明显提高了氮素利用效率和氮素出籽效率.氮素出籽效率与氮素利用效率呈正相关,而与氮素吸收效率呈负相关,与氮素利用率无显著相关关系.氮素营养指数随播期推迟趋于最佳状态,与氮素出籽效率的改善展现出同步性.推迟播期显著降低了花前营养器官氮素转移量和花后氮素积累量,但明显改善了花前营养器官氮素转运效率.氮素出籽效率与氮素转运效率之间存在正相关关系,说明氮素转运效率的改善一定程度上有利于穗部氮素生产籽粒能力的提升.综合来看,适当推迟播期减少了氮素吸收,但提高了氮素利用效率和氮素出籽效率,改善了氮素供应状态.研究结果为本地区冬小麦生产中氮素减施增效的实施提供了理论依据.     

氮高效利用基因型大麦的物质生产与氮素积累特性

通过土培盆栽试验,研究了22份大麦材料在低氮(125 mg·kg^-1)和正常氮(250 mg·kg^-1)处理下氮素吸收利用效率的基因型差异,探讨氮高效大麦干物质生产与氮素积累特性.结果表明： 大麦氮素吸收利用效率基因型差异显著.低氮处理下籽粒产量、氮素籽粒生产效率及氮素收获指数的最高值分别是最低值的2.87、2.92、2.47倍;氮高效基因型大麦籽粒产量、氮素籽粒生产效率和氮素收获指数均显著大于低效基因型,低氮处理下高效基因型3个参数较低效基因型分别高82.1%、61.5%和50.5%.氮高效基因型大麦各生育期干物质和氮素积累优势明显,干物质积累高峰出现在拔节-抽穗阶段,氮素积累高峰出现在拔节前;低氮处理下高效基因型典型材料DH61、DH121+的干物质量较低效基因型典型材料DH80分别高34.4%、38.3%,氮素积累量较DH80分别高54.8%、58.0%.供试大麦干物质和氮素的阶段性积累量对籽粒产量的影响为拔节前最大,且低氮处理下贡献率最高,分别为47.9%和54.7%;而干物质和氮素的阶段性积累量对氮素籽粒生产效率的影响在抽穗 成熟阶段最大,其次是播种-拔节阶段,低氮处理下这两个阶段的贡献率分别为29.5%、48.7%和29.0%、15.8%.氮高效基因型大麦在各生育期的物质生产和氮素积累能力强,低氮处理下优势较为明显,能够提高拔节前干物质生产和氮素积累能力,并协同提高大麦产量和氮素利用效率.     

氮对冬玉米干物质生产及生理特性的影响

通过对不同施氮水平下冬玉米的干物质生产及其生理特性的研究表明 :(1 )随着施氮量的提高 ,叶面积指数增大 ,叶片衰老延缓 ,花后保持有更大的叶面积持续期和光合势 ,有利于干物质的生产 ;(2 )施氮量的增加促进了花丝期前后植株各部分氮和干物质的累积 ,产量显著提高 ,但是营养体干物质和氮的转移率降低 ,尤其高氮条件下尚有大量干物质不能转移 ,库 /源比不协调 ,氮的生产力随之降低。     

基于遥感与模型耦合的冬小麦生长预测

遥感的空间性、实时性与作物生长模型的过程性、机理性优势互补,将两者有效耦合已成为提高作物生长监测预测能力的重要手段之一。提出了一种基于地空遥感信息与生长模型耦合的冬小麦预测方法,该方法基于初始化/参数化策略,以不同生育时期的小麦叶面积指数(LAI)和叶片氮积累量(LNA)为信息融合点将地面光谱数据(ASD)及HJ-1 A/B CCD、Landsat-5 TM数据与冬小麦生长模型(WheatGrow)耦合,反演得到区域尺度生长模型运行时难以准确获取的部分管理措施参数(播种期、播种量和施氮量),在此基础上实现了对冬小麦生长的有效预测。实例分析结果表明,LNA较LAI对模型更敏感,以之作为耦合点的反演效果较好。另外,抽穗期是遥感信息与生长模型耦合的最佳时机,对播种期、播种量和施氮量反演的RMSE值分别达到5.32 d、14.81 kg/hm²、14.11 kg/hm²。生长模型与遥感耦合后的模拟结果很好地描述了冬小麦长势和生产力指标的时空分布状况,长势指标的模拟相对误差小于0.25,籽粒产量模拟的相对误差小于0.1。因此研究结果可为区域尺度冬小麦生长的监测预测提供重要理论依据。