玉米螟杀虫剂的室内筛选

[目的]筛选对玉米螟幼虫和卵具有较好毒杀作用的药剂,为玉米螟的化学防治提供科学依据。[方法]采用人工饲料混药法和浸渍法分别测定10种杀虫剂对玉米螟幼虫和卵的毒杀作用。[结果]印楝素、甲维盐和氯虫苯甲酰胺对玉米螟幼虫具有较高毒力,对3龄幼虫的加50值分别为0．0006,0．0250和0．0387mg／L;印楝素浓度为10．0mg／L时,卵的孵化率为17．80％。[结论]印楝素、甲维盐和氯虫苯甲酰胺可作为玉米螟的防治药剂。     

华北灌溉区秸秆焚烧与直接还田生态效应研究

2年试验研究初步表明,华北灌溉地区夏季麦秸覆盖直接还田较焚烧处理可保持土壤水分,降低土壤温度,有利于玉米的生长发育,作物产量增加。秸秆焚烧初期的土壤速效养分含量(P、K)高于秸秆还田处理,尤其是速效磷含量远高于秸秆还田处理,但至收获时差异不大;秸秆焚烧比秸秆还田处理除草效果好,且可使部分病虫害减轻,但有的病虫害却因秸秆直接还田而加重。     

京郊畜禽粪肥资源现状及其替代化肥潜力分析

随着都市型规模化养殖业快速发展,畜禽粪尿废物大量排放因缺乏足够面积土地消纳所带来的环境压力很大,而粪尿中的氮磷钾养分与化肥一样对作物同等重要,如何合理利用这些废物资源决定了都市化农业的可持续发展。该文针对京郊养殖业和农用地面积现状,结合调研、收集畜禽养分排泄系数和农田养分需求等参数,估算京郊固液粪便养分资源现状及其替代化肥的潜力。结果表明:京郊畜禽固液粪便中N、P、K养分量分别为58.7×103、21.3×103、29.8×103 t,其中固体粪便N、P、K养分分别为43.1×103、20.3×103和19.7×103 t,京郊畜禽固液粪便可分别满足农田N、P、K养分需求量的99.3%、185.2%、62.7%。大部分区县粪肥中P养分产生量超过作物P需求量,粮田秸秆还田可带入的N、P、K养分分别为11.0×103、1.6×103和15.0×103 t,情景分析表明在秸秆还田条件下,按照磷素平衡原则估算本地区所能消纳的粪肥所带入N、P和K养分数量分别为18.3×103、9.9×103和10.3×103 t,同时需要补充N、K化肥分别为29.8×103和22.2×103 t,其余粪肥则需经过堆肥化处理并输往外地。经过堆肥处理,固体粪肥可提供的N、P、K养分分别下降了23%、11%和12%,外输固体粪肥堆肥可进一步减少农田氮磷负荷以及可能的环境风险。     

The drilosphere concept: Fine-scale incorporation of surface residue-derived N and C around natural Lumbricus terrestris burrows

Anecic (deep-burrowing) earthworms are important for soil biogeochemical functioning, but the fine-scale spatial range at which they incorporate C and N around their burrows (the drilosphere sensu stricto) needs to be investigated under realistic conditions. We conducted a field experiment to delimit spatially the extent to which soil around natural Lumbricus terrestris burrows is influenced biochemically. We placed plant litter dual-labelled with ¹³C and ¹⁵N stable isotope tracers on L. terrestris burrow openings and we measured residue-derived ¹³C and ¹⁵N in thin concentric layers (0–2, 2–4, 4–8 mm) around burrows with or without a resident earthworm. After 45 days, earthworms were significantly enriched in ¹³C and ¹⁵N as a result of feeding on the plant litter. At 0–5 cm soil depth, soil ¹⁵N concentrations were significantly higher around occupied than unoccupied burrows, and they were significantly higher in all burrow layers (including 4–8 mm) than in bulk soil (50–75 mm from burrow). This suggests that biochemical drilosphere effects of anecic earthworms, at least in the uppermost portion of the burrow, extend farther than the 2 mm layer assumed traditionally.     

Bacterial salt tolerance is unrelated to soil salinity across an arid agroecosystem salinity gradient

In arid and semi-arid ecosystems, salinization is a major threat to the productivity of agricultural land. While the influence of other physical and chemical environmental factors on decomposer microorganisms have been intensively studied in soil, the influence of salinity has been less exhaustively assessed. We investigated the influence of soil salinity on soil bacterial communities in soils covering a range of salt levels. We assessed tolerance of the bacterial communities from Libyan agricultural soils forming a salinity gradient to salt (NaCl), by extracting bacterial communities and instantaneously monitoring the concentration-response to added NaCl with the Leucine incorporation technique for bacterial growth. To maximise our ability to detect differences in bacterial salt tolerance between the soils, we also repeated the assessment of bacterial growth tolerance after one month incubation with 1 or 2% added organic matter additions to stimulate microbial growth levels. We could establish clear concentration-response relationships between bacterial growth and soil salinity, demonstrating an accurate assessment of bacterial tolerance. The in situ soil salinity in the studied soils ranged between 0.64 and 2.73 mM Na (electrical conductivities of 0.74-4.12 mS cm⁻¹; cation exchange capacities of 20-37 mmol_c kg⁻¹) and the bacterial tolerance indicated by the concentration inhibiting 50% of the bacterial growth (EC₅₀) varied between 30 and 100 mM Na or between electrical conductivities of 3.0 and 10.7 mS cm⁻¹. There was no relationship between in situ soil salinity and the salt tolerance of the soil bacterial communities. Our results suggest that soil salinity was not a decisive factor for bacterial growth, and thus for structuring the decomposer community, in the studied soils.     

Comparison of factors limiting bacterial growth in different soils

Lack of carbon has been assumed to be the most common limiting factor for bacterial growth in soil, although there are reports of limitation by other nutrients, e.g. nitrogen and phosphorus. We have studied which nutrient(s) limited instantaneous growth rates of bacteria in 28 Swedish soils using the thymidine or leucine incorporation technique to measure increased growth rate after adding different combinations of organic carbon (glucose), nitrogen and phosphorus. The soils ranged in pH between 3.1 and 8.9, in organic matter content between 1% and 91% and in soil C/N ratio between 10 and 28. We also tested the effect of adding different amounts of carbon on the bacterial change in growth rate for two soils with different organic matter content. We found that bacterial growth in most of the 28 soils was limited by a lack of carbon, indicated by an increased bacterial growth rate 48 h after adding glucose. In some soils, adding carbon together with nitrogen increased the bacterial growth rates even further. In three soils no effects were seen upon adding nutrients separately, but adding carbon and nitrogen together increased bacterial growth rates. Nitrogen addition tended to decrease bacterial growth rates, while phosphorus addition had little effect in most soils. No correlations were found between the soil C/N ratio, ammonium or nitrate content in soil and bacterial growth limitation, indicating that even soils with a C/N ratio of 28 could be carbon limited. Although the interpretation of the effects of a single limiting nutrient was in most cases straightforward, an interaction between the amount of carbon added and the organic matter content of the soil confounded the interpretation of the extent of a second limiting nutrient.     

稻麦轮作下秸秆还田对稻麦产量和稻田可溶性有机碳含量的影响

为阐明稻麦轮作体系下秸秆还田对作物产量与稻田可溶性有机碳（DOC）的影响,通过连续2年盆栽试验研究了两种典型土壤（壤土和黏土）在无秸秆还田、半量秸秆还田、全量秸秆还田3种处理下稻麦产量和稻季土壤溶液DOC浓度的动态变化。结果表明,秸秆还田显著增加了两种土壤大多数处理的水稻产量,增幅1.6%~11.9%,其中全量秸秆还田的增产效果大于半量秸秆还田（第1年不显著,第2年显著）。秸秆还田对小麦产量的影响因土壤类型而异,壤土中小麦产量显著增加7.2%~10.6%（第1年）或增产不显著（第2年）,但全量秸秆还田和半量秸秆还田处理之间没有显著差异;黏土中小麦显著减产（5.0%~9.3%）,其中第2年的全量秸秆还田减产效应显著大于半量秸秆还田。秸秆还田及土壤类型显著影响水稻前期（烤田之前）的土壤溶液DOC浓度,全量秸秆还田、半量秸秆还田分别比无秸秆还田处理平均增加141.7%、61.9%,壤土比黏土平均增加89.6%;间歇淹水之后,所有秸秆还田处理及土壤类型的DOC浓度均迅速降低。总体上,秸秆还田对两种土壤的水稻增产都有利,但对黏土小麦增产不利,秸秆还田显著增加了稻田前期的DOC浓度,间歇淹水可以迅速降低稻田DOC浓度。     

秸秆深还及配施化肥对土壤腐殖质组成和胡敏酸结构的影响

中国每年农作物秸秆总量巨大,大部分农民选择焚烧,焚烧秸秆会减少表层土壤有机质,损害土壤墒情,引起环境污染,进而危害人类健康。将玉米秸秆施入土壤亚表层(20~40 cm之间),即"秸秆深还"(Corn stover deep incorporation,CSDI),可以有效解决秸秆利用问题,以及由于焚烧秸秆造成的诸多问题,继而达到固碳、蓄水、培肥、稳产的目的。以吉林农业大学试验站玉米连作耕地0~20 cm和20~40 cm土层土壤为研究对象,设CK(未施用秸秆)、CS(秸秆深还)、NPK(单施化肥)、CS+NPK(秸秆深还配施化肥)4种处理,主要研究秸秆深还及配施化肥对土壤腐殖质组成和胡敏酸(HA)结构的影响。腐殖质组成采用腐殖质组成修改法测定,胡敏酸样品采用IHSS方法提取纯化,其结构经元素组成、红外光谱进行研究。结果表明:秸秆深还及秸秆配施化肥对不同土层土壤有机碳(SOC)含量以及腐殖质各组分含碳量均有显著积累作用,PQ值(胡敏酸在腐殖酸中所占的比例)无显著变化。秸秆深还及秸秆配施化肥均能使HA分子的芳香结构比例增加,但CS处理还能同时增加脂族链烃的比例;而CS+NPK处理则使HA的缩合度提高,氧化度下降。说明CS和CS+NPK使HA变稳定的机制有所不同,除了分子结构芳香性提高的作用以外,前者还体现在疏水性的提高上;而后者则体现在分子结构变复杂上。     

稻草不同还田方式对双季水稻产量及稻米品质的影响

通过2年田间定位试验,设置施肥区稻草还田（NPK+S）、 稻草烧灰还田（NPK+SI）和稻草不还田（NPK）以及相对应的不施肥区对照共6个处理,研究了不同稻草还田方式对双季水稻产量及稻米品质的影响。结果表明, 在施用等量氮、 磷、 钾养分条件下, NPK+S处理具有提高早稻分蘖数及成穗率、 中后期叶面积指数及地上部干物质量,增加叶片叶绿素含量（SPAD值）, 增加水稻单位面积有效穗数的显著作用,但对晚稻的作用不明显; 早稻NPK+S处理的产量较其他两个处理两年平均增幅为3.78%~8.77%, 晚稻随着稻草还田次数的增加,NPK+S与NPK+SI处理的产量趋于接近,但较NPK处理增产5.66%~7.32%。不施肥条件下,稻草还田（CK+S）处理对早、 晚稻生长发育的影响明显大于稻草烧灰还田（CK+SI）和稻草不还田（CK）, 且其早、 晚稻产量也极显著高于后两个处理。研究还发现,稻草还田能提高早、 晚稻的稻米食味品质,但降低其外观品质和营养品质以及晚稻稻米的加工品质。以上结果说明,进行稻草全量还田对持续提高双季水稻产量具有重要意义。     

Measurement of ammonia volatilization loss using a dynamic chamber technique: A case study of surface-incorporated manure and ammonium sulfate in an upland field of light-colored Andosol

The present study aimed to elucidate ammonia (NH₃) volatilization loss following surface incorporation (0–15 cm mixing depth) of nitrogen (N) fertilizer in an upland field of light-colored Andosol in central Japan. A dynamic chamber technique was used to measure the NH₃ effluxes. Poultry manure, pelleted poultry manure, cattle manure, pelleted cattle manure and ammonium sulfate were used as N fertilizers for basal fertilization to a bare soil with surface incorporation. All three experiments in summer and autumn 2007 and in summer 2008 showed negligible NH₃ volatilization losses following the application of all N fertilizers with the same application rate of 120 kg N ha⁻¹ as total N; these negligible losses were primarily ascribed to chemical properties of the soil, that is, its high cation exchange capacity (283 mmol_c kg⁻¹ dry soil) and relatively low pH(H₂O) (5.9). In addition, the surface incorporation, the very small ratio of ammoniacal N to total N for the manure, and the decrease in soil pH to ≤5.5 following applications of ammonium sulfate were also advantageous to the inhibition of NH₃ volatilization loss from the field-applied N fertilizers.