The effect of foliar supplements of potassium nitrate and urea on the yield of winter wheat

Winter wheat crops were grown with ostensibly adequate supplies of all soil nutrients in 1990 and 1991 with the aim of testing if late foliar supplements of K and N, applied at key development stages, could improve grain yield and grain N content. Foliar sprays of KNO₃ solution, supplying up to 40 kg K ha^–1 in total, at flag leaf unfolded, inflorescence completed and the watery-ripe stage of grain filling, had no effect on yield, yield components or grain N. Urea, supplying 40 kg N ha^–1 at flag leaf unfolded, had no effects on grain yield and grain N in 1990, but in 1991 grain N was increased by 0.14% whilst yield was reduced by up to 0.6 t ha^–1. Urea scorched flag leaf tips in both years. In 1990, the spring was very dry and foliar supplements might have been expected to have had an effect, but on this highly fertile soil all crop K and N requirements were met from the soil.     

Aflatoxin in Arizona cottonseed: Field inoculation of bolls byAspergillus flavus spores in wind-driven soil

Conditions typical of an Arizona monsoon were mimicked in the field to inoculate cotton plants withAspergillus flavus. Spores, mixed with autoclaved local soil, were blown onto cotton plants having bolls at all stages of maturity, using a modified commercial leaf blower. Half the plants were sprayed with water following inoculation. After one month, plants were pulled and the position of bolls mapped. All bolls were examined for bright-green-yellow fluorescence (BGYF) of lint, and ginned seeds from each boll were assayed for aflatoxin. Control non-wetted, non-inoculated bolls had no BGYF lint and no aflatoxin-containing seed. In contrast, 15% of the bolls from wetted, inoculated plants exhibited BGYF; 18% of these BGYF bolls had toxin. Only 3% of the non-wetted bolls had BGYF lint and none contained toxin. Lower bolls (fully fluffed at inoculation) were not infected, nor were upper bolls (flower stage at inoculation). Infection occurred only in bolls that had opened during the 30 days following inoculation. While the position of BGYF bolls on naturally contaminated plants was the same as for the inoculated, the ratio of toxic bolls to BGYF bolls was different. All BGYF bolls from plants naturally contaminated withA. flavus contained aflatoxin.     

Foliar NPKS application to cotton from full flowering to boll filling

Two field experiments were carried out at different locations to test the effect of NPKS sprays on cotton in addition to soil applied fertilizers. The differences in lint yield and average boll weight between treatments were not significant. Four foliar application (10 kg N, 1 kg P, 3 kg K and 0.5 kg S/ha/application) tended to increase the lint yield and the average boll weight in the location with the lower fertility. It seems that utilization of foliar nutrient application is dependent upon the availability of these nutrients in the soil. N was added mainly as urea, P and K as potassium polyphosphate and S as potassium or ammonium sulphate.Contribution from the Dept. of Soil Chemistry and Plant Nutrition, Agricultural Research Organization. The Volcani Center. Bet Dagan, Israel No 2167-E 1987 series.     

Growth response,yield and yield components of upland cotton (Gossypium hirsutum L) as affected by rates and time of nitrogen application in the Nigerian savannah

Effects of rate and time of nitrogen fertilization on growth, yield and yield components of upland cotton (Gossypium hirsutum L) were studied in two years (1975–76). Four rates of nitrogen application (0, 26, 52 and 78 kg ha^–1) timed at 3 or 8 weeks after sowing were compared. Seed cotton yield components increased significantly with increased N application at least up to 52 kg N ha^–1, with yield increases between 49% and 73%. Seed cotton yield was influenced by treatments mainly through boll number. Both crop growth rate and fruiting were enhanced by nitrogen fertilization. Applying N at 8 weeks (flowering) favoured yield only slightly over that at 3 weeks (thinning), but improved crop growth and fruiting by about 64% and 24%, respectively. There were significant N rate × time interactions in favour of fertilization at flowering. Applying 52 kg N ha^–1 at 8 weeks seems best for cotton in the Nigerian savannah.     

Cotton Plant, Gossypium hirsutum L., Defense in Response to Nitrogen Fertilization

Plants respond to insect herbivory by producing dynamic changes in an array of defense-related volatile and nonvolatile secondary metabolites. A scaled response relative to herbivory levels and nutrient availability would be adaptive, particularly under nutrient-limited conditions, in minimizing the costs of expressed defensive pathways and synthesis. In this study, we investigated effects of varying nitrogen (N) fertilization (42, 112, 196, and 280 ppm N) on levels of cotton plant (Gossypium hirsutum) phytohormones [jasmonic acid (JA) and salicylic acid (SA)], terpenoid aldehydes (hemigossypolone, heliocides H₁, H₂, H₃, and H₄), and volatile production in response to beet armyworm (Spodoptera exigua) herbivory. Additional bioassays assessed parasitoid (Cotesia marginiventris) host-searching success in response to cotton plants grown under various N fertilizer regimes. At low N input (42 ppm N), herbivore damage resulted in significant increases in local leaf tissue concentrations of JA and volatiles and in systemic accumulation of terpenoid aldehydes. However, increased N fertilization of cotton plants suppressed S. exigua-induced plant hormones and led to reduced production of various terpenoid aldehydes in damaged mature leaves and undamaged young leaves. While increased N fertilization significantly diminished herbivore-induced leaf volatile concentrations, the parasitism of S. exigua larvae by the parasitoid C. marginiventris in field cages did not differ among N treatments. This suggests that, despite significant N fertilization effects on herbivore-induced plant defenses, at short range, the parasitoids were unable to differentiate between S. exigua larvae feeding on physiologically different cotton plants that share large constitutive volatile pools releasable when damaged by herbivores.     

Growth,yield components and micronutrient nutrition of field-grown maize (Zea mays L.) as affected by nitrogen fertilization and plant density

Growth and yield components in field-grown maize (Zea mays L.) were enhanced by nitrogen fertilization ranging from 50 to 200 kg N ha^–1. Ear diameter, kernel depth, grain: stover ratio, number of ears plant^–1, plant height and dry matter production increased as N fertilization rate was increased up to 100 or 150 kg N ha^–1. Tasselling in maize was hastened by N fertilization. Increasing plant density from 25000 to 75000 plants ha^–1 increased plant height, dry matter production and delayed tasseling but reduced ear diameter, kernel depth, grain: stover ratio and number of ears plant^–1. Increased N supply and plant density had no influence on the concentrations of Mn, Zn, Cu, and Fe in ear leaf; except that Mn concentration increased as N fertilization rate was increased up to 150 kg N ha^–1. Nitrogen × plant density interactions on the concentrations of the micronutrients in maize ear leaf were not significant.     

1.8%复硝酚钠水剂对棉花生长的调节作用

通过田间小区试验,筛选了1.8%复硝酚钠水剂对棉花生长的调节作用,结果表明:药后10d和20d时,1.8%复硝酚钠水剂均能增加棉花的株高,枝条数和棉铃数。随着药量的增加,1.8%复硝酚钠水剂对棉花株高、枝条数、棉铃数促进作用增加。棉花品质和测产结果表明:1.8%复硝酚钠水剂各处理剂量对棉花的品质没有明显的影响作用,但对棉花的铃重和小区籽棉产量都有所提高。     

Stabilized Double-Stranded RNA Strategy Improves Cotton Resistance to CBW (Anthonomus grandis)

Cotton is the most important crop for fiber production worldwide. However, the cotton boll weevil (CBW) is an insect pest that causes significant economic losses in infested areas. Current control methods are costly, inefficient, and environmentally hazardous. Herein, we generated transgenic cotton lines expressing double-stranded RNA (dsRNA) molecules to trigger RNA interference-mediated gene silencing in CBW. Thus, we targeted three essential genes coding for chitin synthase 2, vitellogenin, and ecdysis-triggering hormone receptor. The stability of expressed dsRNAs was improved by designing a structured RNA based on a viroid genome architecture. We transformed cotton embryos by inserting a promoter-driven expression cassette that overexpressed the dsRNA into flower buds. The transgenic cotton plants were characterized, and positive PCR transformed events were detected with an average heritability of 80%. Expression of dsRNAs was confirmed in floral buds by RT-qPCR, and the T₁ cotton plant generation was challenged with fertilized CBW females. After 30 days, data showed high mortality (around 70%) in oviposited yolks. In adult insects fed on transgenic lines, chitin synthase II and vitellogenin showed reduced expression in larvae and adults, respectively. Developmental delays and abnormalities were also observed in these individuals. Our data remark on the potential of transgenic cotton based on a viroid-structured dsRNA to control CBW.     

Yield,water use and nitrogen uptake for different water and N levels in winter wheat

In an effort to establish an optimum combination of water and nitrogen for winter wheat a field investigation was carried out on a coarse loamy sand soil during 1984–85 and 1985–86 to assess effects of irrigation regime (IR) and N application on yield, water use and N uptake. The treatments compromised all combinations of three irrigation regimes (IR) based on ratios of irrigation water to cumulative pan evaporation viz.1.2 (I-1), 0.9 (I-2) and 0.6 (I-3) and four rates of N, viz. 0, 60, 120 and 180 kg ha^–1. Grain yield increased with increase in frequency of irrigation. In spite of wide differences in weather during the two years, scheduling of irrigation at IW/CPE = 1.2 gave the highest wheat yield on the coarse-textured soil. During 1984–85, the rainless year, grain yield under I-1 was 20 and 32 per cent higher than I-2 and I-3, respectively. With increasing N rate the yield and water use efficiency increased progressively upto 180 kg N under I-1 and upto 120 kg N ha^–1 under I-2 and I-3 regimes. During 1985–86, the wet year, grain yield response to IR was relatively low. Irrespective of IR, yield increased progressively upto 180 kg N ha^–1 during the wet year. Irrigation water regimes and N application also influenced leaf area index and root growth of wheat. The yield of unfertilized wheat was relatively less affected by seasonal rainfall and IR.Both N uptake and grain yield of wheat were found to increase linearly with increase in water use. Water use efficiency was highest under I-1 regime at all levels of N in the dry season of 1984–85 and under I-3 regime in the wet season of 1985–86. Increase in N uptake with increasing N rates was significantly higher under I-1 than I-2 and I-3 regimes. The N use efficiency being maximum at 60 kg N ha^–1, decreased at higher N levels irrespective of IR.     

Semiochemicals from Herbivory Induced Cotton Plants Enhance the Foraging Behavior of the Cotton Boll Weevil, Anthonomus grandis

The boll weevil, Anthonomus grandis, has been monitored through deployment of traps baited with aggregation pheromone components. However, field studies have shown that the number of insects caught in these traps is significantly reduced during cotton squaring, suggesting that volatiles produced by plants at this phenological stage may be involved in attraction. Here, we evaluated the chemical profile of volatile organic compounds (VOCs) emitted by undamaged or damaged cotton plants at different phenological stages, under different infestation conditions, and determined the attractiveness of these VOCs to adults of A. grandis. In addition, we investigated whether or not VOCs released by cotton plants enhanced the attractiveness of the aggregation pheromone emitted by male boll weevils. Behavioral responses of A. grandis to VOCs from conspecific-damaged, heterospecific-damaged (Spodoptera frugiperda and Euschistus heros) and undamaged cotton plants, at different phenological stages, were assessed in Y-tube olfactometers. The results showed that volatiles emitted from reproductive cotton plants damaged by conspecifics were attractive to adults boll weevils, whereas volatiles induced by heterospecific herbivores were not as attractive. Additionally, addition of boll weevil-induced volatiles from reproductive cotton plants to aggregation pheromone gave increased attraction, relative to the pheromone alone. The VOC profiles of undamaged and mechanically damaged cotton plants, in both phenological stages, were not different. Chemical analysis showed that cotton plants produced qualitatively similar volatile profiles regardless of damage type, but the quantities produced differed according to the plant’s phenological stage and the herbivore species. Notably, vegetative cotton plants released higher amounts of VOCs compared to reproductive plants. At both stages, the highest rate of VOC release was observed in A. grandis-damaged plants. Results show that A. grandis uses conspecific herbivore-induced volatiles in host location, and that homoterpene compounds, such as (E)-4,8-dimethylnona-1,3,7–triene and (E,E)-4,8,12-trimethyltrideca-1,3,7,11-tetraene and the monoterpene (E)-ocimene, may be involved in preference for host plants at the reproductive stage.     

百草枯和乙烯利混配对棉花催熟效果好

本试验设计百草枯和乙烯利不同混配比例７个处理，于１９９５年１０月６日在棉花上进行催熟试验。结果表明，每公顷用２０％百草枯水剂６００毫升和４０％乙烯利水剂９００毫升混配对棉花催熟效果最佳，落吐速度、吐絮率，霜前花分别比对照不催熟高５４．４６％、２１．３８％、１４．５１％，幼铃脱落率比用乙烯利单剂下降５２．２０％，亩产比对照提高８．９１％。     

春油菜菌核病药剂防治试验

通过１９９０￣１９９２年药剂防治汨菜菌核病实验表明：以５０％农利灵ＷＰ效果最好。用量１．５ｋｇ／ｈｍ＾２,在盛花期叶面喷雾控制叶部病害效果最佳。     

Die physiologische Ertragsanalyse der Sonnenblume (Helianthus annuus L.) Teil III. Agronomische Faktoren und Produktionstechnik

The Physiological Yield Analysis of Sunflower (Helianthus annuus L.), Part III: Agricultural Factors and Crop Production At enhanced nitrogen (N) supply resp. intraspecific competition dry matter, average yield and leaf area/plant of sunflower are increased resp. decreased. At lower N-supply determination of flower primordia as well as start of flowering are delayed. An increased N-supply resp. higher plant density caused higher variation of positive resp. negative effects on number of achenes/plant than on TKW. Oil content is lowered by increasing N-fertilisation while protein content increased significantly. Optimum sowing date is given when flower initiation takes place under long-day photoperiod. Creation of plant density depends on local water supply and for Europe it is arranged between 5 and 8 plants/m². N-fertilisation should be partitioned to at least two doses. The first dose results at the latest before flower initiation and the second one during the main growing phase. Irrigation before and after flowering is necessary at water deficient locations. Once irrigation has started before flowering it is to be continued absolutly until the post flowering stages.     

Influence of Two Acyclic Homoterpenes (Tetranorterpenes) on the Foraging Behavior of <Emphasis Type="Italic">Anthonomus grandis</Emphasis> Boh

Previous studies have shown that the boll weevil, Anthonomus grandis, is attracted to constitutive and conspecific herbivore-induced cotton volatiles, preferring the blend emitted by cotton at the reproductive over the vegetative stage. Moreover, this preference was paralleled by the release of the acyclic homoterpenes (tetranorterpenes) (E)-4,8-dimethyl-1,3,7-nonatriene (DMNT) and (E,E)-4,8,12-trimethyltrideca-1,3,7,11-tetraene (TMTT) in Delta Opal cotton being higher at the vegetative than at the reproductive stage. Here, we evaluated whether this difference in release of acyclic homoterpenes also occurred in other cotton varieties, and if boll weevils could recognize these compounds as indicators of a specific cotton phenological stage. Results showed that cotton genotypes CNPA TB-90, BRS-293 and Delta Opal all produced higher levels of DMNT and TMTT at the vegetative stage than at the reproductive stage and that these homoterpenes allowed for principal component analysis separation of volatiles produced by the two phenological stages. Electroantennograms confirmed boll weevil antennal responses to DMNT and TMTT. Behavioral assays, using Y-tube olfactometers, showed that adding synthetic homoterpenes to reproductive cotton volatiles (mimicking cotton at the vegetative stage in terms of homoterpene levels) resulted in reduced attraction to boll weevils compared to that to unmodified reproductive cotton. Weevils showed no preference when given a choice between plants at the vegetative stage and the vegetative stage-mimicked plant. Altogether, the results show that DMNT and TMTT are used by boll weevils to distinguish between cotton phenological stages.     

Critical soil level of zinc for wheat grown in alkaline soils

Wheat plants were grown to study the effect of Zn application in a screen house experiment involving 19 alkaline soils having a range of DTPA extractable Zn and widely divergent physical and chemical properties. Soil Zn was positively correlated with organic carbon, clay, Olsen's P and Bray's per cent yield (r = 0.54^*, 0.67^**, 0.54^* and 0.84^**) respectively. There was a significant increase in the leaf, grain and total dry matter yield of plants due to Zn fertilization but no such effect was obvious in stem. Concentration of Zn in different plant parts increased significantly with its application in all the soils irrespective of the initial Zn status. Statistical method indicated 0.65 mg kg^–1 as the critical level of Zn in alkaline soils below which responses to Zn fertilization may be expected in case of wheat.     

Effect of urea management on yield and N use efficiency of lowland rice on an acid sulfate soil

Field experiments were conducted during 1988–1989 at two adjacent sites on an acid sulfate soil (Sulfic Tropaquept) in Thailand to determine the influence of urea fertilization practices on lowland rice yield and N use efficiency. Almost all the unhydrolyzed urea completely disappeared from the floodwater within 8 to 10 d following urea application. A maximum partial pressure of ammonia (pNH₃) value of 0.14 Pa and an elevation in floodwater pH to about 7.5 following urea application suggest that appreciable loss of NH₃ could occur from this soil if wind speeds were favorable. Grain yields and N uptake were significantly increased with applied N over the control and affected by urea fertilization practices (4.7–5.7 Mg ha^–1 in dry season and 3.0–4.1 Mg ha^–1 in wet season). In terms of both grain yield and N uptake, incorporation treatments of urea as well as urea broadcasting onto drained soil followed by flooding 2 d later were more effective than the treatments in which the same fertilizer was broadcast directly into the floodwater either shortly or 10 d after transplanting (DT). The¹⁵N balance studies conducted in the wet season showed that N losses could be reduced to 31% of applied N by broadcasting of urea onto drained soil and flooding 2 d later compared with 52% loss by broadcasting of urea into floodwater at 10 DT. Gaseous N loss via NH₃ volatilization was probably responsible for the poor efficiency of broadcast urea in this study.     

Synchronizing N Supply from Soil and Fertilizer and N Demand of Winter Wheat by an Improved Nmin Method

Excessive nitrogen (N) fertilizer application and poor timing of N fertilizer application to winter wheat are common problems on the North China Plain. To study the possibilities of optimizing the timing and rate of N application, a field experiment was conducted from 1999 to 2001 in a suburb of Beijing. A control (no nitrogen) and two N fertilization strategies (conventional N application and optimized N fertilization) were designed to compare their effects on wheat growth, N nutrient status, grain yield and N balance. The conventional N fertilization strategy was given a fixed N rate of 300 kg N ha⁻¹, which was split, half in autumn and half in spring as a top-dressing. The timing and rate of N and application of the optimized N fertilization strategy were determined by the target value of soil mineral nitrogen demand for three growth periods of wheat, which is related to the target yield, and soil mineral N (N_min) in the effective rooting depth at the beginning of these three periods. Based on the optimized N fertilization strategy, a total of 55 and 65 kg N ha⁻¹ had to be applied to winter wheat in the re-greening and shooting stages of the first and second experimental years, respectively. Compared with the high N rate before sowing in the conventional N fertilization treatment, the optimized N fertilization treatment did not require any N fertilizer before sowing of wheat. Despite a much lower N fertilization rate, no significant difference in N nutrient status, growth during the wheat growing period or grain yield was observed between optimized N and conventional N fertilization treatments. As a consequence of optimizing the rate and timing of the N fertilizer application to match wheat demand, a much lower residual N_min and calculated apparent N loss was found as compared to the conventional N treatment. N recovery for the optimized N fertilization treatment (67% in 1999/2000 and 66% in 2000/2001) was much higher than that of the conventional N fertilization treatment (19% in 1999/2000 and 18% in 2000/2001). In conclusion, the optimized N fertilization strategy can synchronize N demand of wheat and the N supply from soil and fertilizer, and therefore drastically reduce N application rates without any yield losses.     

The efficiency of fertilizer nitrogen in irrigated,direct seeded rice (O. sativa L.) in Europe

Data from 35 experiments with direct seeded rice, performed between 1981 and 1991 by national research institutes in five major rice growing countries of Europe were analyzed to estimate the average efficiency of fertilizer nitrogen (N). Pooled data from a four year regional survey (1984–1988) on rice-based farming systems in the Camargueregion (43° 20'–43° 40' N) in the south of France, were used to perform a similar analysis. Experimentation during two years (1989–1990) was carried out to assess the value of the N-utilization efficiency within the range of N-limited growth and to obtain information on the N-efficiency under controlled conditions.At reduced basal dressing of N on soils with high soil organic matter content, the apparent N-recovery was estimated at 0.21 to 0.32 kg N uptake per kg N applied. Average agronomic efficiency ranged from 12 to 17 kg grain dry mass per kg N applied. High basal N-application on these soils resulted in yield loss. No consistent yield response to fertilizer-N input was found on soils with less than two percent organic matter, irrespective of fertilizer timing. These results confirm the important role of soil organic matter in rice cultivation.An average apparent N-recovery of 0.18 was obtained with split application of N under controlled experimental conditions in the Camargue. Using a controlled release fertilizer, values of 0.58 and 32 kg.kg^–1 were obtained for the apparent N-recovery and agronomic efficiency, respectively. Hence, disregarding the economic feasibility, considerable scope exists for improving N-efficiency in European rice cultivation.     

72%2,4-滴胺盐水剂防除春麦田阔叶杂草

72%2,4-滴胺盐水剂450～750mL·hm-2,于春小麦4叶期喷雾处理,防除阔叶杂草总控制效果达85%以上,对春小麦安全,增产13%以上。     

Nitrogen balances in long-term field experiments

The influence of fertilization with different N doses on nitrate-N content of the deeper soil layers were investigated in soils of long-term experiments at the experimental stations of the National Fertilizer Experimental Network in Hungary. Distribution of nitrate-N with depth was also studied in plots fertilized with different N doses. Although these experiments were set up according to an identical experimental plan at every location, after 20 years of experimentation substantial differences could be detected in the nitrate-N contents, nitrate-N distribution profiles on plots of the same treatments, as well as in the yield and the nitrogen uptake of the cultivated plants at the various sites. These differences are attributed to differences in soil properties and in environmental conditions existing at the individual experimental stations. The conclusions drawn from the data are very important when evaluating the role of nitrogen fertilization in the nitrate-contamination of soils, surface water and groundwater, and for a more precise determination of the N doses to be applied under specific soil and environmental conditions.