大气CO2浓度升高对稻季土壤中麦秸降解及氮素分趋的影响

利用中国唯一的稻麦轮作FACE(free-air carbon dioxide enrichment,开放式空气CO2浓度增高)试验平台,研究大气CO2浓度升高对稻季土壤中小麦秸秆降解速率及其氮素分趋的影响.试验设置Ambient(目前空气对照)和FACE(Ambient+200 μmol·mol-1)两个CO2浓度以及低氮处理(LN,150 kg·hm-2)和高氮处理(HN,250 kg·hm-2)两个氮肥水平,在稻季之初按标记麦秸/土壤重量比0.3%添加15N标记小麦秸秆,根据水稻生长时期依次采样测定秸秆降解速率,并通过分析土壤全氮、植株全氮及其15N丰度来观察已降解秸秆的氮素分趋情况.结果发现,大气CO2浓度升高对高氮处理土壤中小麦秸秆降解速率没有显著影响,但显著促进了低氮处理土壤中小麦秸秆的降解(p < 0.05),使其提高到与高氮处理土壤相当水平;大气CO2浓度升高显著增加了已降解秸秆中氮素的流失,在高氮处理土壤中尤为严重,而对植物吸收已降解秸秆中的氮素没有显著影响.结果表明,大气CO2浓度升高在土壤氮素相对不足时会加速土壤中小麦秸秆的降解,而在土壤氮素相对充足时又会加大降解秸秆中氮素的流失.     

The interaction of protectants with EPTC on field bean, and tri-allate on wheat

Protectants (antidotes) were tested for their potential to protect field beans (Vicia faba L.) from EPTC damage, or wheat (Triticum aestivum L.) from triallate damage. For both crops there was considerable variation in the degree of protection shown from similar treatments in different experiments. For field bean, a seed treatment of 1,8-naphthalic anhydride (NA) at 5 mg/g seed gave some protection from EPTC applied pre-planting at 4–8 kg a.i./ha but not in all experiments. NA also caused marked chlorosis of the foliage. N, N-diallyl-2, 2-dichloroacetamide (R25788) at 20 mg/g seed severely damaged field bean in the absence of herbicide but 5 mg/g gave comparable protection from EPTC to that given by NA and did not cause chlorosis. Mixing R25788 with EPTC in the spray tank gave reduced protection. In a single experiment R4115 (chemistry undisclosed) gave some protection against EPTC damage. For wheat, a seed treatment of 5–20 mg/g NA sometimes countered damage from tri-allate applied pre-planting at 1 kg a.i./ha but not generally from higher doses. R25788 sometimes protected from weight loss due to tri-allate at 1 kg a.i./ha but not from damage symptoms, whereas R4115 at 20 mg/g seed alleviated these symptoms but did not prevent weight loss. R25788 at 4 kg a.i./ha mixed in the spray tank with the herbicide partially reduced weight loss and damage symptoms from a dose of 2 kg a.i./ha. Some treatments of R29148 gave complete protection from tri-allate at 1 kg a.i./ha. The results are discussed in the context of the full data from the two series of experiments.     

Investigations into the movement of glyphosate from treated to adjacent untreated plants

Transfer of glyphosate from treated to adjacent untreated plants was investigated under glasshouse conditions using wheat and Agropyron repens. When glyphosate was used at concentrations characteristic of conventional field application rates, and where shoot contact was prevented, no symptoms were observed on untreated plants. When there was shoot contact, and when glyphosate was used at 2 kg a. i./ha (10 g a. i./litre), phytotoxic effects were observed on untreated plants. At higher concentrations of glyphosate (90 or 180 g a. i./litre), typical of selective applications with ropewick or roller applicators, evidence of root transfer of herbicide was found. In pot experiments these phytotoxic effects were variable, due, perhaps, to variable amounts of root contact. Confining the roots, by growing the plants in tubes, increased the level of phytotoxicity.     

The effect of glyphosate on frond regeneration, bud development and survival, and storage rhizome starch content in bracken

In addition to very effectively suppressing bracken frond regeneration for two years at levels of 2.24 kg a. i./ha and above, glyphosate had considerable effects on the rhizome system. Dry weight of frond-bearing rhizomes, number of living apices and developed buds, number and viability of dormant buds and starch content of storage rhizomes were all markedly reduced. The effects on dormant buds and starch content are particularly important when considering frond regeneration and as a consequence of these, glyphosate is likely to give long lasting control of bracken. Low levels of glyphosate (0.02 and 0.07 kg a. i./ha) did not stimulate bracken growth, while the addition of NH₄SCN apparently inhibited the action of the sub-lethal rate of 0.56 kg a. i./ha.     

Field control of brown leaf rust (Puccinia recondita) of wheat with a triazole compound in north India

RH-124 (4-n-butyl-i,2,4-triazole) when applied as one or two foliar applications (at the rate of i-6 1 a.i./ha) or given by watering soil (at the rate of 0–8 1 a.i./ha) controlled brown leaf rust ( Puccinia recondita ) of wheat in microplot experiments. In north India where the rust appears 80–90 days before harvest, one foliar or soil application was sufficient to mitigate loss in yield. Seed treatment was not found useful when tested in one trial.     

The effect of varying rates of glyphosate and an organosilicone surfactant on the control of gorse

The herbicidal effect of glyphosate applied to gorse (Ulex europaeus L.) was improved by the addition of increasing amounts (0.5–20 g/litre) of Silwet L-77, an organosilicone surfactant. Increasing the rate of herbicide also enhanced control. There was a highly significant interaction between surfactant rate and herbicide dosage; as the amount of Silwet L-77 was increased the rate of glyphosate could be reduced without loss of herbicide efficacy. However, without any added organosilicone surfactant, glyphosate did not provide more than 73% control of gorse at any rate up to 6.5 kg a.i./ha. With the addition of Silwet L-77, complete mortality of all plants could be achieved with 2.2 kg glyphosate/ ha.     

Urea fertilization effects on nutrient uptake and growth of Platanus occidentalis during plantation establishment

Summary The benefit of fertilizer application during establishment of a tree plantation depends on effective nutrient uptake and the utilization of the nutrients in growth. Five urea treatments (0, 50, 75, 150, and 450 kg N/ha) were applied in a completely randomized plot design to a field planted with American sycamore (Platanus occidentalis L.) seedlings to evaluate growth responses and nitrogen use efficiency during the first season of plantation establishment. The site was in the Oak Ridge Reservation in eastern Tennessee on a highly weathered soil. Harvests were conducted on 3 occasions during a 22 week experimental period, and dry weights of stems, leaves, and large and small roots were measured. Chemical analyses were conducted on plant tissues from the 0, 75, and 450 kg N/ha treatments. Plant dry weight increased with urea application and growth analysis showed that this was mainly associated with increase in leaf area and to a minor extent with increase in net assimilation rate. Root weight increased significantly with urea application. The specific absorption rate of roots for several nutrients was greater at higher urea levels for the first 2 harvest periods, but this pattern reversed during the 3rd growth period. Surprisingly, manganese uptake and the specific absorption rate for manganese were enhanced with higher urea application. The acidifying effect of urea nitrification is a likely explanation for the increased Mn availability, and nitrate leaching and/or nitrogen immobilization contributed to low uptake of urea-N by the seedlings. The proportion of the applied nitrogen incorporated into the seedlings was 1.5 and 0.6% for the 75 and 450 kg N/ha urea treatments, respectively. Broadcast fertilizer application is not an effective way of supplying nutrients to seedlings during plantation establishment.     

秸秆全量还田对稻田土壤溶解有机碳含量和水稻产量的影响

以南粳44为供试材料,在粘土和砂土土壤中,设置麦秸秆不还田和全量还田(6000 kg·hm^-2)及3种施氮量(0、225、300 kg·hm^-2)试验,研究了麦秸秆全量还田的腐解率和有机碳释放量动态变化,及其对稻田0～45 cm土壤溶解有机碳(DOC)含量和水稻产量的影响.结果表明： 麦秸秆还田的前期(0～30 d)其腐解率和有机碳释放量最高,腐解率为35.0%(粘土)和31.7%(砂土),有机碳释放率为34.1%(粘土)和33.1%(砂土);30 d后两者均减小.施用氮肥可显著促进秸秆腐解和有机碳释放量,粘土中麦秸秆腐解率和有机碳释放量明显大于砂土.麦秸秆还田后土壤DOC含量逐渐增加,至25 d达最大值,粘土和砂土分别为60.18和56.62 mg·L^-1,此后逐渐减小并趋于稳定.麦秸秆还田处理15 cm处土壤DOC含量显著高于未还田处理,但两者在30和45 cm处土壤DOC含量差异不显著,说明秸秆还田主要增加了稻田0～15 cm土层DOC含量.与不施氮处理相比,施氮处理土壤DOC含量降低,2种施氮处理间差异不显著.秸秆还田减少了水稻前期分蘖发生量,显著降低了有效穗数,增加了穗粒数、结实率和千粒重,显著提高了水稻产量.     

Control of Globodera rostochiensis in Relation to Method of Applying Nematodes

Soaking potato tuber pieces for 15 min in 8,000 μg/ml of oxamyl just before planting reduced the number of Globodera rostochiensis cysts that developed on potato roots, but this treatment was phytotoxic. Five foliar applications of 1.12 kg a.i./ha of oxamyl or carbofuran at 10-day intervals beginning when 90% of the plants had emerged suppressed increase in G. rostochiensis densities. Similar foliar applications of phenamiphos were ineffective in controlling G. rostochiensis. Soil applications (in the row at planting) of aldicarb, carbofuran, phenamiphos, ethoprop, and oxamyl at 5.6 kg a.i./ha reduced the numbers of white females that developed on potato roots, but only those treatments involving aldicarb and oxamyl suppressed G. rostochiensis population increase. Combined soil and foliar treatments did not provide any advantage over soil treatment alone, as soil applications of 5.6 kg a.i./ha alone were equal to, or better than, combined soil (3.4 kg a.i./ha) and foliar (2.2 kg a.i./ha) applications in controlling G. rostochiensis.     

镁、锰、活性炭和石灰及其交互作用对小麦镉吸收的影响

采用盆栽试验,研究了在镉污染土壤上施用石灰、硫酸镁、硫酸锰和活性炭不同用量以及交互作用对小麦生长和吸收重金属镉的影响.研究结果表明,在试验条件下施用适量的硫酸镁、硫酸锰或与石灰配合能明显提高小麦籽粒产量,单施石灰或与活性炭配合施用降低了小麦籽粒产量;与对照(CK)相比,所有处理秸秆产量均下降.施用硫酸镁能显著降低小麦籽粒和秸秆中Cd浓度,且随用量的增加两增大.低量硫酸锰能有效降低小麦籽粒和秸秆中Cd浓度,高量反而增加小麦对Cd的吸收.石灰、活性炭单独施用或配合施用都能明显减少小麦对Cd的吸收,但籽/杆中Cd比却随石灰用量的增加呈明显的上升趋势.叶面喷施硫酸镁对降低小麦吸收镉的效果与土施相当,但叶面喷施硫酸锰却比土施硫酸锰显著降低了小麦籽粒中的镉浓度与吸收量.硫酸镁与硫酸锰,或石灰、硫酸镁和硫酸锰3种物质配合施用,对小麦籽粒镉浓度和吸收量的降低表现出明显的正交互作用,对抑制小麦体内镉从秸秆向籽粒的转移具有显著效果.     

Effect of rates of nitrogen and relative efficiency of sulphur-coated urea and nitrapyrin-treated urea in dry matter production and nitrogen uptake by rice

Summary A field experiment conducted for two rainy seasons (1974 and 1975) on a sandy clay loam soil at the Indian Agricultural Research Institute, New Delhi showed that at 100kg N/ha the apparent recovery of urea nitrogen by the rice crop was only 28%, which was raised to 41.7% by treating urea with Nitrapyrin and to 47.4% by coating urea withneem (Azadirachta indica Juss) cake. The recovery with sulphur-coated urea was 37.7%. Dry matter production nitrogen concentration in plant and uptake by rice were increased as the rate of nitrogen was increased from 0 to 150kg N/ha. Advantage of treating urea with Nitrapyrin or coating withneem cake was seen more in grain than straw yield.     

N-lignin and margosa (neem) seed cake-blended urea as nitrogen source for wheat

Summary In a field experiment on wheat, N-lignin was found as effective as urea in increasing grain yield and nitrogen uptake by the crop. N-lignin also left higher amount of fertilizer residue in the hydrolysable organic-N fraction in the soil than did urea. The effect of margosa (neem) seed cake blended urea on the grain yield, N uptake and soil N was similar to ordinary urea. Supplementing N-lignin with urea did not show any advantage.Phosphorus uptake by wheat crop was enhanced and potassium uptake was depressed by application of N-lignin. Neem seed cake also stimulated phosphorus uptake slightly but had no effect on potassium uptake.     

Control of potato cyst-nematode, Heterodera rostochiensis, in three soils by small amounts of aldicarb, Du Pont 1410 or Nemacur applied to the soil at planting time

Aldicarb or Du Pont 1410 (S-methyl 1-(dimethylcarbamoyl)-N-[(methylcarbamoyl) oxy] thioformimidate) at 2.6–11.2 kg a.i./ha applied to the soil at planting time controlled potato cyst-nematode, Heterodera rostochiensis, in sandy loam, peaty loam and silt loam and greatly increased tuber yields of susceptible potatoes. Nemacur (O-ethyl-O-(3-methyl-4-methylthiophenyl) isopropylamido-phosphate) controlled potato cyst-nematode in sandy loam at 2.9–10.3 kg a.i./ha and in silt loam at 11.2 kg a.i./ha but did not control the nematode well in peaty loam even at 22.4 kg a.i./ha. In peaty loam aldicarb and Nemacur were more effectively incorporated by rotavation than by a modified power harrow.     

Efficacy of Aldicarb to Rotylenchulus reniformis and Biodegradation in Cotton Field Soils

The microbial degradation of aldicarb was examined in the greenhouse using soil from four cotton fields with a history of aldicarb use. The addition of aldicarb at 0.59 kg a.i./ha to natural soil increased Rotylenchulus reniformis numbers 6.6% in one soil and decreased R. reniformis numbers only 25.8% in another soil as compared to the corresponding natural soil without aldicarb. The use of increasing rates of aldicarb did not increase the efficacy of aldicarb in these soils. Rotylenchulus reniformis numbers were reduced 39.8, 22.6, and 6.8%, and increased 5.7% for aldicarb applied at 0.29, 0.59, 0.85, and 1.19 kg a.i./ha, respectively, in one natural soil. In another natural soil, R. reniformis numbers were reduced 42.5 and 21.9% for aldicarb applied at 0.29 and 1.19 kg a.i./ha, respectively, but increased 19.1 and 10.6% for aldicarb applied at 0.59 and 0.85 kg a.i./ha, respectively. Autoclaving the soils restored aldicarb toxicity in both soils, and R. reniformis numbers were reduced 96 and 99%, respectively, as compared to autoclaved soil without aldicarb. Bacterial populations were greater in the natural soils where aldicarb did not reduce R. reniformis numbers relative to the same soils that were autoclaved. However, no bacterial species was consistently associated with aldicarb degradation.     

Control of pea cyst-nematode, Heterodera goettingiana, by small amounts of aldicarb, Du Pont 1410, Ciba-Geigy 10576 or Dowco 275 applied to the soil at planting time

Aldicarb, or Du Pont 1410 (S-methyl-I-(dimethylcarbamoyl)-N-[(methyl-carbamoyl)oxy]thioformimidate), at 2.8–22.4 kg a.i./ha incorporated in the seed-bed before sowing greatly increased the yield of peas in a clay loam and two sandy clay soils infested with pea cyst-nematode, Heterodera goettingiana, and lessened or prevented increase in the number of nematodes. CibaGeigy 10576 (an organophosphorus compound) at 5.6–22.4 kg a.i./ha was similarly effective in a sandy clay soil. Dowco 275 (O, O-diethylO-(6-fluoro-2 pyridyl) phosphorothioate) at 5.6 or 11.2 kg a.i./ha also controlled the nematode well in the clay loam and in a sandy clay soil but although it greatly increased the yield of peas in the clay loam, it did not increase yield in the sandy clay.     

A greenhouse study on the effect of inoculation of N-fixing blue-green algae in an alluvial soil treated with P and Mo on the yield of rice and changes in the N-content of soil

Summary The efficiency of the inoculation of three cultures of N-fixing blue-green algaeviz. (i)Aulosira fertilissima (A₁), (ii)Nostoc muscorum (A₂) and (iii) their mixture (A₃) in increasing the grain and straw yield of rice, nitrogen uptake in grain and nitrogen content in soil was studied in a green house experiment with an alluvial soil in presence or absence of urea nitrogen application. Inoculation significantly increased the grain and straw yield of rice and nitrogen uptake in grain, but the efficiency of inoculation gradually decreased with the increase in the levels of urea nitrogen application, the extent of decrease varying with the algal cultures inoculated. The nitrogen content in the soils after the crop harvest recorded a significant increase due to inoculation but after air drying the soil a marker decrease of the same was observed, which indicated that most of the nitrogen added to the soil by blue-green algae through fixation did not persist after air drying the soil.     

Nitrogen immobilization by rice straw incorporated in lowland rice production

Summary The nitrogen supplying power of rice straw for flooded rice production was studied in three field experiments. The net nitrogen immobilization was observed to be 0.54 per cent of the original dry weight of the straw as determined by grain yield responses over single growing seasons. Straws with higher nitrogen concentrations increased grain yield on nitrogen deficient soil, and straws with lower nitrogen concentrations depressed yield.Supplemental nitrogen applied in either urea or vetch resulted in yield increases in the presence of both high and low nitrogen straws. No significant immobilization of supplemental nitrogen was found to result from straw applications.The net nitrogen immobilization percentage obtained in these experiments is approximately one-third the average of values obtained by other workers. We infer that the anaerobic environment of the flooded rice field and its associated bacterial microflora are the cause for the lesser nitrogen requirement for the field decomposition of rice crop residues.     

Amelioration of growth reduction of lowland rice caused by a temporary loss of soil-water saturation

Decreases in nutrient availability after loss of soil-water saturation are significant constraints to productivity in lowland rainfed rice soils. The effectiveness of soil amendments like lime and straw in ameliorating these constraints are poorly understood. This pot experiment was conducted in Cambodia to investigate changes in soil chemical properties and nutrient uptake by rice after applying lime or straw to continuously flooded or intermittently flooded soil. In continuously flooded soils, exchangeable Al decreased to below 0.2 cmolc/kg. Liming (pH 6.5–6.8) the continuously flooded soil decreased the levels of acetate extractable Fe and P, plant P uptake and shoot dry matter, but had no effect on either Bray-1 or Olsen extractable P values. By contrast, the addition of straw (3.5 g dry straw/kg soil) increased Bray-1, Olsen, and acetate extractable P, plant P uptake, shoot P, and shoot dry matter. The non-amended soils became strongly acidic after loss of soil water saturation: extractable Al increased to 1.0 cmol_c/kg, a potentially harmful level for rice. By contrast, extractable P decreased markedly under loss of soil water saturation as did plant P uptake, shoot P, and shoot dry matter. With loss of soil water saturation, liming substantially depressed the levels of Al but it did not increase plant P uptake, shoot P, and shoot dry matter. Straw addition not only decreased extractable Al levels to well below 0.6 cmol_c/kg under loss of soil water saturation, but it also increased extractability of soil P, plant P uptake, shoot P, and shoot dry matter. Thus, in rainfed environments, the incorporation of straw may be more effective than liming to pH 6.8 for minimising the negative effects of temporary loss of soil-water saturation on P availability, P uptake, and growth of rice.     

Cd、Zn、Pb及其相互作用对烟草、小麦的影响

烟草对Cd、Zn、Pb是一种敏感性作物,Cd、Zn、Pb对烟草的影响比对小安、水稻都大。 Cd、Zn、Pb在烟草各器官中的累积随土壤Cd、Zn、Pb浓度的增高而增大。 Cd、Zn、Pb在烟草各器官中含量的次序为:茎叶>根>籽粒。它们在根中受阻,而较易转移到茎叶和籽粒中。 烟草对Pb的吸收比对Zn和Cd明显地低。Pb仍然是一种低吸收性元素。 土壤Zn增加,减低了烟草对Cd的吸收,而土壤Pb的增加,则促进了烟草对Cd的吸收。