Field trials with D-D mixture against potato-root eelworm

A D-D mixture has been tested against Heterodera rostochiensis at seven 2-acre sites on sands, silts and blackland soils. Apart from a pilot trial where soil was injected in spring, injections were carried out in the autumn, and potatoes were grown the following year. Factors investigated were rate of application (0, 200, 400 and 800 lb. D-D/acre), depth of injection (4 or 8 in.) and the effect of rolling after injection. At the most responsive of the sites (Wainfleet), increases in yield, kill, and the post-crop eelworm population were all roughly proportional to the rate of application. Under favourable circumstances a 50% increase in yield and something like a 50% reduction in eelworm population 4 weeks after injection can be expected from 800 lb./acre, but the reduction is more than made good during the growth of the subsequent crop; accelerated multiplication of eelworm on the treated plots leads to their having a larger population than the untreated controls at lifting time. Of the sites tested, the blackland soils gave a lower eelworm kill and a much lower yield increase from D-D than silts or sands. After autumn injection the nematocidal, and probably the phytocidal, effects of D-D persist in the soil for many weeks. The hypochlorite method of 'hatching' eelworm larvae for counting has proved unreliable.     

The effect of pot size on growth and transpiration of maize and soybean during water deficit stress

Many experiments are conducted in greenhouses or growth chambers in which plants are grown in pots. Considerable research has shown that pots can have a limiting effect on overall plant growth. This research was undertaken to examine the effects of pot size specifically on transpiration response of maize (Zea mays L.) and soybean (Glycine max L.) plants undergoing water-deficit stress. Maize and soybean experiments were conducted similarly, but as separate experiments. Maize plants were grown in 2.3, 4.1, 9.1, and 16.2 l pots sealed to prevent water loss except by transpiration. For each pot size, plants were divided into two watering regimes, a well-watered control and a water-deficit regime. Water deficits were imposed by simply not rewatering the pots. Soybean was examined in a similar manner, but only the three larger pot sizes were used in the experiment. For both maize and soybean, and in both watering regimes, there was a significant reduction of shoot dry weight and total transpiration with decreasing pot size. However, there were no significant differences among pot sizes in the fraction of transpirable soil water (FTSW) point at which transpiration began to decline (FTSW0.31 for maize and 0.35 for soybean) or in the overall relationship of transpiration rate to soil water content in response to water deficits. These results indicated that, regardless of pot size or plant size, the overriding factor determining transpirational response to drought stress was soil water content.     

Assessing the agronomic and environmental effects of the application of cattle manure compost on soil by multivariate methods

Multivariate analysis was used for interpreting data from a pot experiment using samples of three Spanish soils. Samples of soil fertilized with compost were compared with untreated control samples. We also compared the effect of adding the compost to soil with a controlled moisture content of 50% of its water holding capacity (WHC), and to a near-saturated soil (95% WHC). Hierarchical cluster analysis (HCA) and principal component analysis (PCA) were used; they perfectly differentiated sample groups both as a function of the treatment applied and by sampling date. The compost samples were characterized by higher pH, electrical conductivity (EC), organic matter (OM) content and cation exchange capacity (CEC), together with nutrient concentrations than the control pots. The pots with a soil–compost mixture at 95% WHC presented lower values of EC, CEC, inorganic N, K, Na and B than the mixtures at 50% WHC. Multivariate methods may therefore be useful for the analysis and interpretation of a large number of data in soil research.     

The effect of container porosity on root environment and plant growth

Summary Comparison of clay and plastic pots for tomato propagation in six experiments showed plastic pots to give significantly better results than clay pots in winter and the converse to be true in summer. In each experiment the ratio of plant growth (dry weight) in clay and plastic pots was related to both the mean daily solar radiation and the mean outside night minimum temperature. In winter, plants in both types of container made significantly more growth when stood on open benches than when stood on benches with solid surfaces. These differences in growth were related to soil temperature, clay pots being cooler than plastic pots, the temperature difference between the types of pot ranging from approximately 1°C by night in winter to 4°C under high intensity solar radiation in summer. In winter, soil temperatures were often below the optimum, and in summer in excess of the optimum. By day, temperature within the pots showed highly significant correlation with solar radiation, and by night in winter pot temperature was negatively correlated with the difference between the glasshouse and the outside air temperature. Well-defined horizontal thermal gradients were found, and these were positively correlated with soil temperature. In wet soils the thermal gradients were less than in dry soils, and because of their higher thermal conductivity wet soils were warmer than dry soils. When the normal evaporative cooling from the porous walls of clay pots was prevented by a bituminous coating, the soil temperature during the night was not significantly different from that in plastic pots. By day, however, soil temperature in non-evaporating clay pots was less than that in evaporating clay pots, due to the lower thermal conductivity of the dry clay wall.     

Growth and transpiration of maize and winter wheat in response to water deficits in pots and plots

Pots used for experiments conducted on plants grown in them create rooting environments that are affected by limited soil volume, which can affect various physiological processes, including transpiration, and plant growth. However, the applicability of results from pot experiments to the field has received limited attention. The objective of this study was to compare the growth and transpiration of maize (Zea mays L.) and winter wheat (Triticum aestivum L.) when grown in pots and field plots under various constant water deficits. The experiments were conducted under similar environmental conditions for both pots and plots. Transpirational responses at both transient (RTTr) and daily (RDTr) time scales to a decreasing fraction of available soil water (FASW) were analyzed. For a comparable FASW, there was a significant reduction in shoot dry weight and total transpiration for plants in pots compared to those in plots. A parabolic relationship between shoot dry weight and total transpiration existed and was not influenced by soil volume or crop type. The plot experiment data for both crops was consistent with pot data for the response of RDTr and RTTr to changes in FASW, which was represented by a linear-plateau function. However, the threshold values were significantly different for the two time scales. The threshold values and slopes of the linear-plateau function for maize and wheat were not significantly different in the response of RTTr to FASW, but were significantly different in the response of RDTr to FASW. Therefore, the transpirational responses of the selected maize and winter wheat hybrids to soil drought were different at the daily and transient time scales.     

EFFECTS OF REPEATED FIELD INJECTIONS OF D-D MIXTURE AGAINST POTATO-ROOT EEL-WORM

Autumn injections of D-D mixture have been annually repeated for three years on a silt soil at Moulton (Holland, Lincolnshire) and a black fen soil at Prickwillow (Ely, Cambridgeshire), with different results. At Moulton there was an increased yield of tubers each time D-D was used, with no significant residual effects after the first year, and no marked long-term effect on the eelworm population. At Prick-willow D-D gave an increased yield in the first season only, with no positive residual effects on yield, and an apparent stimulating effect on the eelworm population. At Moulton in 1948 and 1950 (but not in 1949) the cost of the D-D treatment was heavily outweighed by the value of the resultant increase in crop. However, on the organic soil at Prickwillow D-D treatment was ineffective in 1949 and 1950 and the eelworm population, initially higher than at Moulton, remained at a level inducing failure of the potato crops.     

MOVEMENT OF EELWORMS

Experiments on vertical migration through saturated soil fractions, horizontal migration through soil fractions at different pressure deficiencies and migration in single layers of particles showed that the beet eelworm, Heterodera schachtii Schmidt, attained maximum speed when the pore diameters were between 30–60 μ. Speed of the eelworms increased as lateral displacement of the body was restricted by external resistances acting perpendicularly to the body axis; at the maximum speed there was no lateral movement, each part of the body following the part immediately in front of it. The speed of beet eelworm larvae in water films of various thickness was measured; maximum speed occurred in a film 2–5 μ thick. Four arbitrarily classified types of progression were observed in the pore spaces. It is suggested that the 'moisture characteristic' supplies most of the information required about the physical properties of the soil in relation to eelworm movement. By examining such a curve the pore size distribution can be ascertained and the probable behaviour of beet eelworm larvae in the medium predicted.     

Pot size affects expression of Mn efficiency in barley

Mn efficiency is defined here as an ability of a genotype to grow and yield well in a soil which is limiting in available Mn for a standard genotype (Graham, 1984). Screening for Mn efficiency in soil-based pot testing had been producing inconsistent results, and thus improvement of pot screening became an objective. One possible factor, pot size was examined as the cause, using two sizes of pot. In large pots, the expectation of higher dry matter and shoot Mn concentration in a Mn-efficient genotype compared to a Mn-inefficient genotype was realised over a wide range of Mn supply, whereas in small pots, the genotypic differences were expressed at only one, low rate of Mn supply (10 mg kg soil^-1). Plants in the small pots strongly responded to root restriction by decreasing yields and increasing root/shoot ratios and Mn concentrations of shoots. The critical value of Mn concentration for shoot growth was not affected by the small pots, but the Mn mobilization by plants might be affected in the small pots. The practical outcome of these results is that using an adequate size of pot and measuring the Mn concentration of shoots, soil-based pot screening for Mn efficiency can be improved.     

三维土壤异质性对种子萌发影响的实验研究

三维土壤异质性对种子萌发影响的实验研究 种子萌发受其生长环境的影响，但土壤异质性对种子萌发的作用还不太清楚。本文通过控制实验研究了三维土壤异质性对草本植物种子萌发的影响，实验设置了两种水平的土壤异质性，即通过在花盆内的三维空间上相间填充营养丰富和贫瘠两种土壤来构建不同的土壤异质性水平。两种水平土壤异质性的斑块大小分别为7.5和15.0 cm。实验采用两种草本植物(黑麦草Lolium perenne和垂穗披碱草Elymus nutans)，每种植物选择大小一致的种子50粒，这些种子要么放在异质性土壤中萌发，要么放在培养皿中萌发。实验过程中，每天统计这些种子的萌发率。实验发现，斑块小的花盆内种子萌发率较低，这个结果与我们的预期相符，我们认为斑块小的花盆内，两种土壤斑块之间的间距较小，植物遭遇不同土壤斑块资源变动的几率较大，植物为了减小这种变动带来的不利影响，会倾向于降低萌发率和延迟萌发。我们的研究还发现，斑块小的花盆内种子萌发的变异性也较大，即与大斑块内的种子萌发率相比，小斑块内的种子萌发率在各重复间的差异性较大。与二维土壤异质性相比，三维土壤异质性更接近于真实情况，这样的土壤设置能够促进我们更好地理解土壤空间异质性对种子萌发等动态过程的影响.     

Petroleum-degrading microbial numbers in rhizosphere and non-rhizosphere crude oil-contaminated soil

Phytoremediation can be a cost-effective and environmentally acceptable method to clean up crude oil-contaminated soils in situ. Our research objective was to determine the effects of nitrogen (N) additions and plant growth on the number of total hydrocarbon (TH)-, alkane-, and polycyclic aromatic hydrocarbon (PAH)-degrading microorganisms in weathered crude oil-contaminated soil. A warm-season grass, sudangrass (Sorghum sudanense (Piper) Stapf), was grown for 7 wk in soil with a total petroleum hydrocarbon (TPH) level of 16.6 g TPH/kg soil. Nitrogen was added based upon TPH-C:added total N (TPH-C:TN) ratios ranging from 44:1 to 11:1. Unvegetated and unamended controls were also evaluated. The TH-, alkane-, and PAH-degrading microbial numbers per gram of dry soil were enumerated from rhizosphere and non-rhizosphere soil for vegetated pots and non-rhizosphere soil populations were enumerated from non-vegetated pots. Total petroleum-degrading microbial numbers were also calculated for each pot. The TH-, alkane-, and PAH-degrading microbial numbers per gram of dry soil in the sudangrass rhizosphere were 3.4, 2.6, and 4.8 times larger, respectively, than those in non-rhizosphere soil across all N rates. The presence of sudangrass resulted in significantly more TH-degrading microorganisms per pot when grown in soil with a TPH-C:TN ratio of 11:1 as compared to the control. Increased plant root growth in a crude oil-contaminated soil and a concomitant increase in petroleum-degrading microbial numbers in the rhizosphere have the potential to enhance phytoremediation.     

土壤水分对强筋小麦‘豫麦34’氮素同化酶活性和籽粒品质的影响

 以强筋型小麦(Triticum aestivum)品种‘豫麦34号’为材料,采用盆栽方法研究了土壤水分对氮素同化酶活性及籽粒品质的影响。结果表明：旗叶硝酸还原酶（NR）活性于花后呈下降趋势,且土壤含水量为田间持水量（FC）60%的处理活性最强,其次为40%FC,活性最低的是80%FC。旗叶和籽粒中谷氨酰胺合成酶（GS）活性于开花15 d前均呈下降趋势,15 d后均为上升趋势,各水分处理间酶活性大小关系是：80%FC＞60%FC＞40%FC。各水分处理间旗叶和籽粒谷氨酸合成酶（GOGAT）活性的大小关系同GS。60%FC籽粒产量及品质最优,80%FC产量次之,40%FC产量最低;40%FC品质次之,80%FC品质最低。不同水分处理下籽粒蛋白质含量与叶片NR、GS 和籽粒GOGAT活性均呈正相关,与旗叶GOGAT活性呈负相关。且40%FC和80%FC下籽粒蛋白质含量只与旗叶GS活性相关性达显著水平, 60%FC下蛋白质含量则与旗叶NR和籽粒GS活性均达显著相关,与旗叶GS活性达极显著相关。     

Ca(NO3)2对NaCl胁迫下木麻黄扦插苗生理特征的调控

用不同浓度 Ca(NO3) 2 · 4 H2 O(0 .7、1.4、2 .1g Ca2 / kg土 )对 1年生的处在两种 Na Cl胁迫 (10和 2 0 g/ kg)处理下的木麻黄扦插苗进行化学调控 ,研究硝酸钙盐加氯化钠处理的木麻黄幼苗的生长量、木麻黄幼苗抗氧化酶系统活性和渗透调节物质的含量的变化 ,研究结果表明 :中度 Na Cl胁迫加硝酸钙处理下的木麻黄扦插苗的可溶性蛋白质含量增加 ,MDA含量降低说明膜脂过氧化作用减轻 ,而且抗氧化酶活性 (SOD、POD)之间协调变化有利于提高清除自由基的速率 ,中度盐胁迫下钙盐可以促进木麻黄体内脯氨酸的积累 ;但重度 Na Cl胁迫下钙盐对木麻黄的调控作用不显著 ,重度盐胁迫下钙盐反而降低木麻黄 SOD、POD活性和脯氨酸的含量 ,减弱了抗氧化酶系统对活性氧的清除作用 ,同时高浓度钙盐还会加重 Na Cl胁迫对木麻黄幼苗的损伤 ,这说明适量的钙盐有利于木麻黄幼苗抵抗盐胁迫能力的提高 ,而高浓度钙盐则可能会加重盐胁迫     

Limitations to CO2-induced growth enhancement in pot studies

Recently, it has been suggested that small pots may reduce or eliminate plant responses to enriched CO₂ atmospheres due to root restriction. While smaller pot volumes provide less physical space available for root growth, they also provide less nutrients. Reduced nutrient availability alone may reduce growth enhancement under elevated CO₂. To investigate the relative importance of limited physical rooting space separate from and in conjunction with soil nutrients, we grew plants at ambient and double-ambient CO₂ levels in growth containers of varied volume, shape, nutrient concentration, and total nutrient content. Two species (Abutilon theophrasti, a C₃ dicot with a deep tap root andSetaria faberii, a C₄ monocot with a shallow diffuse root system) were selected for their contrasting physiology and root architecture. Shoot demography was determined weekly and biomass was determined after eight and ten weeks of growth. Increasing total nutrients, either by increasing nutrient concentration or by increasing pot size, increased plant growth. Further, increasing pot size while maintaining equal total nutrients per pot resulted in increased total biomass for both species. CO₂-induced growth and reproductive yield enhancements were greatest in pots with high nutrient concentrations, regardless of total nutrient content or pot size, and were also mediated by the shape of the pot. CO₂-induced growth and reproductive yield enhancements were unaffected by pot size (growth) or were greater in small pots (reproductive yield), regardless of total nutrient content, contrary to predictions based on earlier studies. These results suggest that several aspects of growth conditions within pots may influence the CO₂ responses of plants; pot size, pot shape, the concentration and total amount of nutrient additions to pots may lead to over-or underestimates of the CO₂ responses of real-world plants.     

Remediation of Ammonium-Contaminated Abandoned Animal Waste Lagoon Soil: Physical Properties and Growth of Barley

Remediation of the soil beneath closed animal waste lagoons is an important issue, particularly for lagoons in environmentally sensitive regions. Few studies address the possibility of using plants to remediate these soils. The objectives of this research were to determine whether barley (Hor-deum vulgare L.), a salt-tolerant crop, would grow in lagoon soil and to determine the effect of plant residue amendments on barley growth and soil physical properties. The lagoon soil was collected from a closed swine lagoon. Oat-straw and corn-cob residues were added at rates of 0 (control), 15, 30, 45, 60, and 75?g/kg lagoon soil. Barley grew in all soils, including the soil with no residues. Average grain yield of plants in pots with oat straw was more than twice that of plants in pots with corn cobs (10.7?g/pot and 4.5?g/pot, respectively). Bulk density and oxygen diffusion rate decreased with increasing amounts of residue in the soil. Infiltration was lower in pots with oat straw than in pots with corn cobs. Irrigation water moved rapidly through macropores visible in the soil with corn cobs. The soil amended with corn cobs retained less water, causing poor growth of the barley. The results showed that corn-cob residue created preferential flow paths in the lagoon soil.     

Some effects of the flowerpot on plant growth

Summary This investigation has thus shown that while pots from various sources differ but little in appearance, there are considerable differences in the permeability of the walls, due fundamentally to variations in the pore size. The characteristic features of porous pots in that there is a continuous current of soil solution outwards from the soil through the pot wall, the rate of this current increasing with permeability. Air to replace this water enters the soil at its upper surface, thus, the extent to which the soil is aerated is indirectly determined by the permeability of the pot. This increased aeration has been shown to lead to an increased rate of nitrification in the soil, together with an increase in the available potash, resulting in greater plant yields. Good aeration of the soil also had a beneficial effect on root development.Thus, in general, high permeability is advantageous in pots, unless it is so great as to lead to such rapid drying of the soil that the plant suffers drought effects. Such detrimental effects are particularly likely to occur under extreme conditions of high temperature and low humidity.Another important point, emphasized in this study is the large demand of the pot plant for nitrogen in comparison with the small amount of soil explorable by its roots. Addition of nitrogen is therefore desirable in any case, while for impermeable pots in particular, it is advisable that such nitrogen should be directly assimilable rather than in an organic form.     

Mineralization of15N-labelled legume residues in soils with different nitrogen contents and its uptake by Rhodes grass

Summary Soil was collected from pots that had grown 1,3 or 6 soybean (Glycine max) or Siratro (Macroptillium atropurpureum) crops that had received organic residue returns from each crop.¹⁵N-labelled residues were added to half the pots in the experiment and the other half left unamended. Half of each group was then sown to Rhodes grass (Chloris gayana) which was grown, under glasshouse conditions, for 12 weeks.Ten grams of organic matter residues were added to each pot (1.5 kg soil) and the pots subjected to two wetting and drying cycles. At the end of the second wet cycle, soil mineral N values ranged from 6 to 64 ppm in unamended soils and from 19 to 177 ppm in amended soils. These levels generally declined over a 12 week period both in the presence and absence of sown grass.Nitrogen uptake by the grass increased with the number of previous cycles and was higher in Siratro than soybean soils. Recovery of¹⁵N by plant growth from the incorporated soybean residues was little effected by previous crop history and averaged 15.4%. On the other hand, Siratro recoveries were 13.7, 42.4 and 55.5% from soils that had grown 1, 3 and 6 previous Siratro crops, respectively.The addition of organic residues stimulated the release of native organic N (positive priming effect) on all soils.These results show that the turnover rate of nitrogen from organic residues can be high and the net result of these additions depends on the nature of the organic residues and the soil system to which they are added. These data emphasise the need to consider the rate of nutrient turnover from organic sources rather than concentrate on the nature and size of the resident nutrient pools.     

Combinatorial mixture synthesis and biological evaluation of dihydrophenyl triazine antifolates.

The traditional 'one-pot' three component synthesis was adapted successfully for combinatorial mixtures synthesis of dihydrophenyl triazines, which are nonclassical, dihydrofolate reductase (DHFR) inhibitors. Each library was designed to comprise eight reaction mixture pots and in every pot there were three dihydrophenyl triazines. A total of three libraries were synthesized and the final number of compounds harvested was 64. The products precipitated out of the reaction mixture and could be collected easily and cleansed by washing. Solid supports and further purification processes were not required. The reactions were monitored by TLC and a HPLC method was developed to determine the number of products in each pot. All 24 pots were screened for inhibitory activity against the rat liver DHFR. Two pots showed good inhibitory activity and the products in them were individually synthesized, characterized and biologically tested again. One lead compound was identified amongst all the compounds synthesized, and would be further optimized.     

氮肥形态对冬小麦根际土壤氮素生理群活性及无机氮含量的影响

采用大田盆栽方法研究了硝态氮肥、铵态氮肥、酰胺态氮肥3种氮肥形态对冬小麦品种豫麦50生育中后期(拔节期、开花期、花后14 d、花后28 d)根际土壤氮转化相关微生物活性、酶活性和根际土壤NH+4离子、NO-3离子含量的影响。结果表明:随着生育期的推进,除脲酶外,氨化细菌、硝化细菌、亚硝化细菌、反硝化细菌和蛋白酶活性变化的均为"倒V"型变化特征,以花后14 d活性最强;而脲酶活性在拔节期最强,并且其活性远大于其它微生物及酶。氮肥形态对根际土壤氮素生理群及无机氮的影响不同。酰胺态氮肥促进了根际氨化细菌、反硝化细菌、脲酶、蛋白酶的活性,而硝化细菌、亚硝化细菌在硝态氮肥条件下活性较强。除拔节期外,土壤中NH+4离子在铵态氮肥处理下含量较高,NO-3离子在酰氨态氮肥处理下含量较高。因此,酰胺态氮能够促进小麦根际土壤有机氮的分解,硝态氮肥可以促进土壤中氨的转化,以利于小麦根系的吸收与利用。氮肥形态主要是通过影响土壤中氮素生理类群及酶的活性,从而影响土壤中无机氮的含量。     

MOVEMENT OF EELWORMS

Tracks were plotted of about 300 individual eelworms comprising six species among water droplets on a glass surface. Measurements of the tracks indicated that the product of length and activity of an eelworm divided by its speed was a constant. This supports the hypothesis that the speed of an eelworm among water droplets is a function of its length and activity. This principle can only be applied to movement in soil where the length of the eelworm is less than about three times the particle diameter. Under such conditions the eelworms move in thin films or water droplets over particles. Among smaller-sized particles the speed of the eelworms is influenced by particle size. With increasing eelworm length there is an increase in soil particle size for maximum mobility.     

利用发光酶基因标记技术跟踪棉花根圈中的绿针假单胞菌PL9L

采用细菌转化和杂交的方法,成功地将全套发光酶基因标记系统Tn7luxCDABE引入绿针假单胞菌(Pseudomonas chlororaphis)PL9,得到稳定的发光标记菌PL9L。采用发光菌落平板计数法和X射线胶片自显影法,通过盆栽试验和盒裁试验,研究了发光标记菌PL9L在棉花根圈的定殖动态和分布规律。盆栽试验结果表明,在灭菌土盆栽中,播种后6d左右PL9L在棉花根圈的定殖水平达最高(31×109cfu/g根土),播种后56d左右趋向稳定,PL9L数量为17×102cfu/g根土;未灭菌土盆载中,播种后8d左右PL9L的定殖水平达最高(11×109cfu/g根土),46d左右趋向稳定,菌数为14×102cfu/g根土。盒栽试验结果表明,PL9L可从种子向根尖方向扩散,但并不与根的伸长生长同步,播种后36d,灭菌土盒栽中PL9L可扩散至种子下方120cm以内,而未灭菌土盒栽中PL9L扩散至110cm以内。在棉花根尖区域均未检测到PL9L。