Effect of Different Preceding Crops and Crop Rotations on Yield of Winter Oil-seed Rape (Brassica napus L.)

To determine the effect of different preceding crops and crop rotations on the grain yield of oil-seed rape, a long-term rotation experiment was conducted at the Hohenschulen experimental station in Kiel, NW Germany. Additional factors included the nitrogen fertilization and the fungicide application. The results reported herein are based upon the harvest years 1988 to 1993. Averaged over the different rotations and husbandry treatments, the grain yields in the 6 experimental years varied between 2.71 t ha^?1 and 3.99 t ha^?1. In contrast, the effect of the different husbandry treatments was smaller and non significant. Averaged over 6 years, only the fungicide application caused small yield increase of 0.2 t ha^?1. The highest grain yields of 3.77 t ha^?1 or 3.65 t ha^?1 occurred when oil-seed rape was directly following peas. Low yields between 3.15 tha^?1 and 3.33 tha^?1 were obtained when oil-seed rape was grown after oilseed rape. The lowest grain yield of 3.13 t ha^?1 was produced with oil-seed rape grown in monoculture only. In rotations with oil-seed rape following a preceding cereal crop (wheat or barley), the grain yields averaged between 3.22 tha^?1 in a two course rotation and up to 3.44 tha^?1 in a four course rotation. In general, the yields of oil-seed rape increase with the length of the rotation and the length of the break between two oilseed rape crops. The yield component number of seeds per m² was affected by the previous cropping accordingly, whereas the thousand seed weight did not respond to the cropping history. Based upon disease assessments in the first years of this experiment, we argue that an increase in the incidence of fungal diseases has considerably contributed to the yield decrease of oil-seed rape in short rotations.     

The Effect of Different Preceding Crops on the Development, Growth and Yield of Winter Barley

Reliable estimations of the yield response of winter barley to different preceding crops are necessary for the design of crop rotations.
The grain yield and yield components of winter barley (cv. Tapir ) following either rapeseed, oats, wheat or barley were determined in five years of field experiments on a sandy loam (Luvisol) at the Hohenschulen experimental station near Kiel, Germany, F.R. The growth, development and incidence of take-all ( Gaeumannomyces graminis var. tritici ) was measured in a total of three years. On average over the five years barley grown after oats yielded 0.8 t per ha (11 %) more than barley following wheat which was mainly due to a higher number of ears per m². Barley following either oats or rapeseed produced a higher dry weight and a larger number of tillers per m² compared with barley grown after wheat or barley. This effect was already-present at the sampling date before winter. Take-all ratings were constantly higher in barley following a susceptible crop, but only reached a severe level late in the season and therefore could not explain the observed differences in growth, development and subsequently grain yield. Since no other pathogens affected the development other non-pathogenic causes must be considered as main causes for the described observations and yield differences.     

前作、土壤有效氮及烤烟施氮对烟叶产量和产值的影响

针对玉溪田烟前作蔬菜面积增加及其肥料用量较大,对后作烤烟的施肥及烟叶产质量产生明显影响的实际问题,于2004-2006年采用大区试验方法开展相关试验研究。结果表明：在同一土壤有效N水平内及施N量基本相近的条件下,小麦及油菜、蚕豆、大蒜及叶菜类、菜豌豆等不同前作的烤烟产量、产值及中上等烟比例有明显差异。烤烟施N量,除考虑土壤有效N含量外,还要考虑前作;烤烟前作为大蒜、叶菜类、菜豌豆等施氮量较大的田块,要严格控制烤烟的施氮量;提出了土壤有效N及不同前作与烤烟施N量的关系表,丰富和完善了烤烟科学施肥的内涵。     

Effect of Presprouting on Yield of Maincrop Potatoes (Solanum tuberosum L.) in Organic Farming

From 1991 to 1993 field trials at two sites (Bruchkobel and Gladbacherhof) were carried out to study the coti-tribtition of presprouting in securing the yield of main-crop potatoes (cvs. Agria. Granola. Linda and Nicola) in organic farming. In several cases presprouting diminished significantly the number of stems and tubers per plant. While in July (sample harvest) presprouting resulted in significant higher total yields with nearly all cultivars, in September (main harvest) the presprouting effect on total yield differed from year to year and partially from site to site, Presprouting reduced the percentage of undersized tubers, especially in 1992. Significant increases of the percentage of oversized tubers caused by presprouting were found especially with cv. Agria. The presprouted potatoes showed significantly higher marketable yields in 1991 at Bruchkobel (+28%), in 1992 at Bruchkobel (+ 14%) and Gladbacherhof (+ 18%) and in 1993 at Bruchkobel (+ 3%), Considerable yield increases caused by presprouting were observed when the foliage was destroyed early in the growing season by the Colorado beetle (Bruchkobel 1991) or by late blight (both sites 1992). Presprouting proved to be an important method to ensure yields in a farming system using no chemical pesticides.     

Germination Responses of Cañahua (Chenopodium pallidicaule Aellen) to Temperature and Sowing Depth: A Crop Growing Under Extreme Conditions

Cañahua (Chenopodium pallidicaule) is grown in the Altiplano of Bolivia and Peru, between 3810 and 4200 m a.s.l. Rural indigenous households have cultivated the cañahua as a subsistence crop for millennia. The seeds have a high content and quality of protein. We studied the relation between the following: (i) temperature and seed germination and (ii) the effect of temperature and sowing depth on seedling emergence of five cultivars and one landrace. Three experiments were conducted as follows: (i) seeds of a cultivar were germinated in Petri dishes at six temperatures (3, 5, 10, 14, 20 and 24 °C), (ii) sown at five depths (0, 5, 10, 25 and 50 mm) in a mixed peat soil substrate at three temperatures and (iii) one landrace (Lasta) and 5 cultivars (Lasta and Saihua growth habit) were sown in 6 depth (0, 5, 10, 25, 35 and 50 mm) in a sandy loam at two temperatures (5 and 15 °C). Temperature had significantly effect on the germination percentages of the plants (P < 0.001). Seeds germinated at the lowest temperature (3 °C). The estimated base temperature was close to 0 °C. A polynomial function described well the relation between time to 50% germination (t₅₀) and temperature in the interval from 3 to 24 °C resulting in a linear relationship between germination rate and temperature. Shallow sowing depth (5–25 mm) resulted in 80% germination at 15 °C. There were significant differences of emergence in relationship to burial depth (P < 0.001). Only few seedlings emerged when seeds were sown at 50 mm depth. We did not find significant differences in emergence of seedlings between Lasta and Saihua at 15 °C. Nevertheless, at 5 °C, seedlings of cañahua belonging to the Lasta growth habit form did have higher germination rate as were shown for the Kullaca cultivar and the Umacutama landrace. This may be attributed to larger seed size of these cultivars.     

施氮对涝渍胁迫下作物生长和产量影响的研究进展

随着气候变化的加剧,涝渍灾害发生的频率和强度不断增加,严重制约着作物的可持续生产。充分挖掘作物自身潜力,提高其对水分胁迫等非生物逆境的抵抗力是适应气候变化的内在要求。随着作物抗逆生理生化机制研究的深入,人们越来越重视施氮在作物抗逆中所发挥的重要作用。为了进一步了解氮肥对涝渍条件下作物生长和产量的调控效应及调控机制,本文总结了涝渍胁迫对作物地上部光合作用、抗氧化酶活性、膜质氧化作用、内源激素含量、根系生长及产量形成的影响及其氮素调控效果,明确了氮肥施用调控作物生长和产量形成的生理机制,指出了氮肥调控涝渍胁迫下作物生长和产量研究中存在的问题,在此基础上笔者指明了未来的一些研究方向,如应用新型氮肥、现代高科技技术、培育氮高效且抗逆的品种等提高作物的抗逆性。     

蔗糖对不同基因型马铃薯试管苗生长和长期保存的影响

研究不同蔗糖浓度对四个基因型马铃薯试管苗生长和长期保存的影响,为培育马铃薯健壮试管苗和长期保存马铃薯种质资源提供理论依据。以‘大西洋’、‘夏波蒂’、‘克新一号’和‘费乌瑞它’四个不同基因型马铃薯脱毒试管苗为试验材料,测定在不同蔗糖浓度下及经长期保存后恢复生长的马铃薯试管苗相关生理指标。结果表明:随着蔗糖处理浓度的增加,四个基因型马铃薯株高、有效节位数及腋芽萌发率均出现先增加后降低的生长趋势,当蔗糖浓度达到3%～4%时,除‘克新一号’外其余三个基因型均达到了最大值,6%的蔗糖浓度对‘大西洋’、‘夏波蒂’和‘费乌瑞它’的生长有明显的抑制作用;3%～6%的蔗糖浓度均能有效促进‘克新一号’的正常生长,8%的蔗糖浓度对其生长有显著的抑制作用;同时随着蔗糖浓度的增加均能有效延长四个基因型马铃薯试管苗的保存时间,当蔗糖浓度达到10%时,经保存一年均能达到90%以上的存活率,随着保存时间的延长其存活率又会有所下降。因此,3%的蔗糖浓度适合于‘大西洋’、‘夏波蒂’和‘费乌瑞它’基础苗扩繁,4%的蔗糖可作为三个基因型的壮苗培养基;4%的蔗糖浓度可同时作为‘克新一号’的扩繁和下地培养基;10%的蔗糖浓度可将四个基因型马铃薯脱毒试管苗的保存时间延长至1年,存活率均可达到90%以上,且长期保存后对试管苗继代生长无影响。本研究通过系统研究蔗糖对马铃薯试管苗生长和长期保存的影响,既有助于降低马铃薯试管苗工厂化生产成本,同时还可规避传统保存法造成的耗时耗工、种质资源易丢失等弊端,降低以植物生长抑制剂保存马铃薯种质造成的成活率低、变异率高等不安全因素。     

不同前茬对烤烟生长、产量和质量的影响

以烤烟K326品种为材料,在石林和寻甸两个不同气候生态点通过田间试验研究了一年两熟条件下油菜、小麦、大麦、绿肥和休闲5种前茬对烟株生长及烟叶产量、质量的影响。结果表明,不同前茬明显影响烟株的生长、成熟、产量、产值和评吸质量,且因生态区不同而有差异。前茬为小麦,两个试点烤烟均表现出前期生长较快、后期落黄较好;前茬为绿肥,烤烟前期生长较慢、后期生长过旺、落黄较迟;前茬为绿肥或休闲地,两试点烤后烟叶产量最高;但产值在石林点则以前茬为大麦、绿肥或油菜,寻甸点以前茬为大麦、绿肥或小麦的处理为最好。烟叶评吸质量在石林以油菜或小麦为前茬、寻甸以小麦或绿肥为前茬的处理最佳。综合而言,烟株生长期间气温较高的石林烟区烤烟前茬以油菜为宜,而气候冷凉的寻甸烟区则以小麦或绿肥为最佳前茬。     

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

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

不同施肥模式对菜稻轮作产量和菜田氮磷平衡的影响

通过马铃薯-毛豆-晚稻轮作制2 年定位田间试验,研究不同施肥模式对菜稻轮作产量和菜田氮磷浓度的影响。结果表明：经济施肥使三季作物获得显著增产效果,一个轮作周期下净增收比CK处理增加23.7%,比习惯施肥处理增加10.5%。一个轮作制中,氮磷肥表观利用率分别达到60.5%和16.0%,比习惯施肥提高了15.6 个百分点和7.3 个百分点。马铃薯-毛豆连作在经济施肥下,土柱渗漏水硝态氮和总磷浓度分别比基础土壤提高了63.3%和30.6%,但与晚稻轮作后,土柱渗漏水硝态氮和总磷浓度与基础土壤大致持平。因此,菜稻轮作结合经济施肥是菜田养分管理的有效技术模式。     

外源锌对氮胁迫下薏苡幼苗生长及抗氧化系统的影响

为缓解薏苡氮胁迫伤害,为缺氮地区薏苡栽培提供参考依据。以贵州省黔西南薏苡种子为试验材料,采用盆栽试验方法,测定分析外源锌与氮胁迫对薏苡幼苗形态生长、叶绿素含量、生物量积累与分配、过氧化氢酶(CAT)、过氧化物酶(POD)活性及丙二醛(MDA)积累的影响。结果表明,（1）缺氮时薏苡幼苗株高、根长、主根数、总叶片数及各部分生物量显著下降（P<0.05,下同）,致使总生物量较对照显著降低80.65%,CAT、POD活性受到显著抑制,MDA含量显著增加26.29%。（2）施锌显著增加了薏苡株高、叶面积及茎生物量,叶绿素含量整体呈上升趋势,CAT、POD活性显著提高;同时,根系对外源锌表现较为敏感,其根长显著降低28.09%,而主根数显著增加16.86%;（3）缺氮施锌显著提高缺氮薏苡幼苗株高和根长,增幅分别为20.30%、17.72%,抗氧化酶CAT活性显著提高171.01%,而对POD活性及MDA积累影响不大。研究认为,氮胁迫下施锌能促进薏苡幼苗生长和抗氧化系统的平衡,提高薏苡幼苗的适应能力,在一定程度上缓解了氮胁迫所导致的不良影响。     

The Effect of Different Shade Levels on Growth and Tuber Yield of Sweet Potato: II. Tuber Yield

Eight sweet potato cultivars ( Ipomoea batatas Lam.) were grown under four different light regimes (0, 26, 42 and 60 % light reduction (LR)) at two experimental sites of the International Potato Center (CIP) in Peru during the 1990 and 1991 growing season. Increasing shade diminished the tuber yield of five cultivars, two showed a tolerance for slight (26 % LR) and moderate (42 % LR) shade and one had the same yield in full sunshine and slight shade. Shade mainly reduced the sink-size (tubers m ⁻²) of sweet potato and to a lesser extent the sink-strength. The growth of the plant top was hardly affected by shade; slight shade even favoured shoot development of some cultivars. The plant top was the stronger sink under shade conditions and tuber yield was not only reduced by lesser assimilate production as a whole but also by an altered assimilate partitioning.     

Drip Irrigation Frequency: The Effects and Their Interaction with Nitrogen Fertilization on Maize Growth and Nitrogen Use Efficiency under Arid Conditions

Differences in soil moisture and wetting pattern under different irrigation frequencies mean that vegetative growth and nitrogen use efficiency in maize can differ even when the same total amount of irrigated water is applied under different frequency regimes. The goal of this study was to evaluate the effects of drip irrigation frequency and its interaction with nitrogen fertilization on vegetative growth and nitrogen use efficiency of a maize crop at different growth stages and on grain quality at maturity stage in a sandy soil. The experiment was conducted for 2 years (2005 and 2006) using a randomized complete block split–split plot design with four irrigation frequencies (once every 2, 3, 4 and 5 days), two nitrogen levels (190 and 380 kg N ha^?1) and two maize hybrids (three‐way cross 310 and single cross 10) as the main‐plot, split‐plot and split–split plot variables, respectively. Irrigation water, totalling 524 mm ha^?1, applied for each irrigation frequency was divided into 28, 21, 17 and 14 doses for the F2, F3, F4 and F5 treatments, respectively. Results indicated that vegetative growth, crop growth and nitrogen efficiency parameters at the 10‐leaf and tasseling growth stages increased with increasing drip irrigation frequency, whereas grain protein content decreased. Although the values of the vegetative growth and crop growth parameters increased with increasing nitrogen levels, significant decreases in nitrogen efficiency parameters were also observed indicating the need for further optimization with a reduced nitrogen application rate. Significant interaction effects between irrigation frequency and nitrogen levels were detected for all parameters measured. In most cases, the parameters were not significantly different between the two nitrogen levels at an irrigation frequency of once every 5 days, but did differ significantly at irrigation frequencies of once every 2, 3 or 4 days. The relationship between the nitrogen use efficiency parameters and retained available soil water content at the 10‐leaf and tasseling growth stages was best represented by a second order polynomial equation with an R² ranging from 0.73 to 0.98. Based on our findings, an irrigation frequency of once every 2 and 3 days is recommended to enhance growth and nitrogen use efficiency of drip‐irrigated maize in sandy soil in Egypt.     

The Effect of Seed-Tuber Physiological Age and Cultivar on Early Potato Production

Enhancing physiological aging of seed‐potatoes has the potential to substantially affect production, especially for short‐season growing areas. This study analysed the effect of seed‐tuber age and cultivar, jointly, to identify the combination for optimum early crop production, based on field experiments conducted at two locations in Nova Scotia, Canada. The potato cultivars Superior, AC‐Novachip, Niska, and Yukon Gold were aged by exposing seeds stored at 4 °C to warming periods of 0, 242 (3 weeks), and 484 (6 weeks) day‐degrees, prior to planting. Cultivar and age levels were completely randomized within each location and replicated four times. Harvest periods at 65, 80 and 95 days after planting (DAP) were analysed as an unbalanced split‐plot factorial, with year as a random blocking factor, location as a whole plot treatment, and cultivar and age crossed as subplot treatments. Total yield and marketable yield from Yukon Gold improved with physiological age when harvested early at 65 and 80 DAP, while that from AC‐Novachip improved when aged only 3 weeks. Niska was not affected by age. Overall, AC‐Novachip was consistently better than the remaining cultivars, regardless of age. The best treatment combination that maximized marketable yield was Yukon Gold aged 6 weeks planted at a commercial farm and harvested 95 DAP. For early harvest (65 DAP), however, AC‐Novachip aged 3 weeks and Yukon Gold aged 6 weeks generated the highest yields. Niska and Superior generated lower yield and higher culls.     

Effect of Water Stress on Physiological Attributes and their Relationship with Growth and Yield of Wheat Cultivars at Different Stages

The effects of water stress on physiological attributes of drought‐sensitive (Kalyansona) and drought‐tolerant (C‐306) wheat cultivars were studied in a pot experiment. Water stress was imposed by withholding irrigation at boot and anthesis stages. Leaf water potential, leaf osmotic potential and leaf turgor potential (measured with pressure chamber and osmometer), as well as leaf diffusive resistance, leaf transpiration rate and leaf‐to‐air transpiration gradient (measured with a steady‐state porometer) were measured diurnally. Growth and yield parameters were recorded after harvesting of the crop. Triplicate data were analysed using a completely randomized design and correlations amongst these parameters were computed. Water stress was found to reduce diurnal leaf water potential and leaf osmotic potential in both the genotypes but leaf osmotic potential was significantly higher in the drought‐tolerant cultivar C‐306 than in the drought‐sensitive cultivar Kalyansona. Positive turgor was recorded in both the genotypes under water stress and non‐stress conditions. Water‐stressed plants showed significantly lower turgor potential than control plants. In diurnal observations, water‐stressed plants exhibited significantly higher leaf diffusive resistance in both genotypes at both stages. The diffusive resistance of C‐306 was predominantly higher than that of Kalyansona. Water stress decreased leaf transpiration rate at both stages but the reduction was higher at the anthesis stage. The leaf‐to‐air temperature gradient was much higher in C‐306 than in Kalyansona at the boot stage but at the anthesis stage genotypic variation was non‐significant. The capacity to maintain cooler foliage was lower at the anthesis stage than at the boot stage in both the cultivars. Shoot dry weight, number of grains, test weight, grain yield, biological yield and harvest index decreased to a greater extent when water stress was imposed at the anthesis stage, while imposition of water stress at the boot stage caused a greater reduction in plant height and number of tillers. Similarly, water stress caused a smaller reduction in growth, yield and yield attributes in C‐306 than in Kalyansona. In general, the correlation coefficient of grain and biological yield with water potential and its components was positive and highly significant. Similarly, turgor potential was also correlated positively and significantly with grain yield at both the stages, but with biological yield it was significant only at the anthesis stage. A negative and significant correlation was obtained for diffusive resistance and leaf‐to‐air temperature gradient with grain yield at the boot and anthesis stages. The rate of transpiration was also positively and significantly correlated to grain and biological yields at both the stages. Amongst the yield attributes, number of leaves and number of tillers were positively correlated at the anthesis stage, whereas leaf area and shoot dry weight were significantly correlated with grain and biological yields at both the stages.     

Analysis of Water Supply of Plants Under Saline Soil Conditions and Conclusions for Research on Crop Salt Tolerance

Abstract In the dry areas of the world there is an increasing pressure to apply low quality brackish waters for plant irrigation (agriculture, horticulture, landscape greening). Consequently there is a demand to improve salt tolerance of conventional crops and to develop adequate irrigation techniques too. The efforts in the past decades to approach the understanding of salt stress mechanism by focusing on biochemical and physiological research were disappointing with respect to progress for crop growth and yields under saline soil conditions. However, it is generally agreed by all disciplines involved in research for crop salt tolerance that under saline soils conditions the reduced water supply of crops is the most critical growth factor. The paper presents some model calculations and field investigations that demonstrate the effect of root water uptake on the salinity of the root surrounding soil fraction (rhizospheric soil). It is shown that root hair length and rhizospheric soil volumes are factors most relevant for understanding crop salt tolerance, when growing in soils. It is postulated that short root hairs contribute to a lower salt tolerance (onions), whereas long root hairs enhance water uptake from saline soils and crop salt tolerance (rape). As interactions between roots and soil contribute to the salt tolerance of crops under field conditions, it is doubtful that selection for salt tolerant varieties and breeding for salt tolerance under conditions of water and flow culture experiments is very efficient. Breeding for more salt-tolerant crops and brackish irrigation techniques should consider root morphology and soil/root contact zone.     

限水灌溉下不同氮肥用量对小麦产量及氮素分配利用的影响

研究了限水灌溉下不同氮肥用量对冬小麦产量和氮素分配利用的影响。结果表明 :氮肥利用率随氮肥量的递增而降低 ,施 2 2 5kg/hm2 纯氮处理达到最高产量 ,在此基础上增施氮肥产量下降 ;随着施氮量的增加 ,植株体内的氮素较多地分配于营养器官 ,地上部器官叶片占的比例最大 ,而收获指数依次降低     

不同施肥条件下苜蓿产量、氮素累积量及肥料氮素利用率研究

旨在探讨不同施肥条件对苜蓿干草产量、植株全氮含量、植株氮素累积动态以及肥料氮素利用率等指标的影响。采用田间小区试验方法,共设5个处理：不施肥对照处理( CK )、单施化肥处理( CF )、化肥与牛粪混施处理(DM1)、化肥与沼液混施处理(DT)和减量化肥与牛粪混施处理(DM2)。结果表明,施用氮肥不仅可以增加苜蓿干物质量和氮素累积量,而且由于大幅增加苜蓿刈割前期的干物质和氮素累积速率而可能缩短其刈割周期、增加年刈割次数;多次刈割的综合结果证实在施用化学氮肥的基础上再增施有机肥仍存在增产的空间,但有机肥由于其活性氮素含量低而不能完全替代化学氮肥。在有机、无机配施情况下,化学氮肥的表观利用率为46.7%~48.1%,腐熟牛粪的氮素利用率为~9.1%,而沼液的氮素利用率为~13.8%,因此,苜蓿生产中有机肥的氮素利用率明显低于化学氮肥。     

包膜尿素对甜瓜产量、氮素吸收和氮肥利用率的影响

采用基质盆栽试验研究了包膜尿素与普通尿素对甜瓜产量、氮素吸收和氮肥利用率的影响.包膜尿素-次性接触施肥于幼苗根部.结果表明:包膜尿素处理的甜瓜产量显著(P<0.01)高于常规施氮处理,增产19.2%-19-4%;相比常规施氮,施用包膜尿素显著降低了果实硝酸盐含量(P<0.05);常规施氮处理的植株叶片叶绿素含量在追肥前后出现较大波动.而包膜尿素处理在甜瓜生长期间均比较稳定;甜瓜植株氮素吸收曲线与包膜尿素氮素释放规律吻合;施用包膜尿素较常规施氮提高氮肥利用率1.1～20.6个百分点.综上所述,施用包膜尿素能实现增产、提高氮肥利用率以及改善品质的目的,是一种有应用前景的新型肥料.     

基施有机肥替代无机氮肥分蘖肥后移对水稻产量及生长的影响

为研究有机肥替代无机N肥的有效途径,以主推粳稻品种“南粳5055”为材料,利用小区试验研究基施有机肥替代无机N肥分蘖肥后移对水稻产量及生长的影响。结果表明：基肥不施无机氮肥或者施用有机肥替代无机N肥高峰苗数会增加,会推迟高峰苗出现时间。有机肥替代无机N肥使抽穗期剑叶、倒2叶、倒3叶叶基角变小,倒3叶叶长增加,延缓抽穗后顶三叶叶绿素含量的下降速度,通过增加有效穗数、千粒重实现增产,对水稻农艺性状影响不大,主要影响是株高。