减量灌溉条件下缓释肥料对番茄产量、品质及硝态氮淋溶的影响

为考察减量灌溉下2种缓释肥料对番茄产量、品质、氮素利用及硝态氮淋溶的影响,小区试验设置农民习惯灌溉量(W100%)和减量灌溉30%(W70%)两个灌溉量处理;不施氮肥(CK)、普通尿素(U)、氮素30%施用包膜尿素(CU30%)、氮素50%施用包膜尿素(CU50%)、氮素30%施用生物炭基氮肥(BCU30%)5个肥料处理。结果表明:减量灌溉30%番茄产量和品质没有显著影响,但显著降低土壤氮素淋溶,相同施肥处理40~60 cm土层硝态氮减少8.0%~63.7%;2种缓释肥料显著提高番茄产量,CU30%、CU50%、BCU30%番茄产量比施用尿素(U)分别提高19.4%~22.1%、21.5%~22.6%、14.5%~15.3%;氮肥利用率提高10.1%~12.4%、10.2%~12.7%、2.3%~4.0%;番茄硝酸盐含量降低6.3%~14.4%、3.0%~7.9%、12.4%~13.3%;2种缓释肥增加番茄果实番茄红素含量,提高番茄糖酸比,改善番茄品质;2种缓释肥减少氮素淋失,40~60 cm土壤硝态氮含量分别比尿素常规施肥降低28.7%、20.0%和75.0%;因此,设施番茄种植中,滴灌节水条件下农民的习惯用量还具有节水潜力,而氮肥以30%~50%缓释肥基施,能实现番茄高产、减少氮素的淋失和提高肥料利用效率。     

滴灌施肥技术对生姜产量及水肥利用率的影响

为提高生姜产量和水肥利用效率,该文以‘莱芜大姜’为试材,研究了常规沟灌不施肥（CK0）、常规沟灌施肥（CK）、滴灌等量施肥（T1）及滴灌减量施肥20%（T2）等不同灌溉施肥方式对生姜生长及水分和氮磷钾利用率的影响。结果表明,滴灌施肥有利于生姜植株各器官的平衡生长,虽然生物产量与常规沟灌施肥无显著差异,但T1、T2的根茎经济产量分别比CK提高17.94%和15.78%。T1、T2的氮钾吸收量分别比CK增加12.54%、13.53%和6.09%、7.01%,而磷素吸收量T1、T2与CK间无显著差异;T1、T2的氮磷钾利用率分别比CK提高19.85%、12.38%、19.66%和37.06%、30.66%、37.76%;T1、T2的灌溉水利用效率分别比CK提高112.71%和110.64%。表明滴灌施肥处理可显著提高生姜根茎产量、氮磷钾的吸收量和利用率以及水分的利用率。     

含氨基酸水溶肥料和EM微生物菌剂对设施莴笋生长和品质的影响

以莴笋为供试材料,研究在莴笋叶面喷施、根部灌施EM微生物菌剂和含氨基酸水溶肥料对其植株生长、光合特性、产量和果实品质的影响。本试验设4个处理:不施用任何肥料(CK)、常规施肥处理(T1)、喷施+灌施EM微生物菌剂(T2)、喷施+灌施含氨基酸水溶肥料(T3)。试验结果表明:与对照CK相比,喷施+灌施EM微生物菌剂和喷施+灌施含氨基酸水溶肥料能显著提高莴笋的株高和茎粗,有效促进作物的生长;从光合特性看,T3处理的光合速率、气孔导度、胞间CO2浓度和蒸腾速率均显著优于对照CK,和常规施肥T1相比也有明显提高,说明喷施+灌施含氨基酸水溶肥料能提高莴笋的光合作用。产量上,T3T2T1CK,T1、T2和T3的产量相较于CK的增长幅度分别为20.17%、26.05%、31.65%,T2和T3相较于T1的增长幅度分别达到4.90%和9.99%,T3相较于T2的增长幅度为4.44%,表明EM微生物菌剂和含氨基酸水溶肥料均能提高莴笋的产量,而含氨基酸水溶肥料的效果更佳。     

不同施肥处理对红玉杧及土壤的影响

为了解不同施肥方案对红玉杧及土壤理化性质的影响,并为贵州红玉杧提质增效及改善土壤环境提供参考依据,以贵州种植5年的红玉杧为试材,共设计3个处理,处理1(CK)采用当地常规的施肥方法,处理2(T1)在常规施肥的基础上增施硫酸钾肥,处理3(T2)在常规的施肥基础上增施硫酸钾肥和海藻肥。分析不同施肥处理对果树茎粗、产量、果实品质、叶片和果实养分含量、土壤理化性质的影响。结果表明:T1、T2处理单株增产效果显著,较CK处理分别提高了15.61%、19.09%;主成分分析表明,T1、T2处理的综合得分明显高于CK处理,说明增施硫酸钾肥和海藻肥对果实品质改善效果明显。从叶片、果实、土壤养分分析结果来看,T1、T2处理叶片中钾、镁、铜、锌含量都能得到明显的改善,显著高于CK处理;钙含量CK处理显著高于T1、T2处理;果实中除氮元素外,CK处理的养分含量均高于T1、T2处理。T2处理土壤中的有机质比CK处理增加了106.73%,速效钾含量比CK处理提高了782.08%,但是T2处理的有效磷含量却比CK处理降低了92.78%。增施硫酸钾肥和海藻肥后,T1、T2处理总产值分别增加了15.55%、19.08%,VCR(施肥后增加农产品所得价值与施肥增加开支的比值)分别为12.12、5.53,从产投比而言是划算的,对提升红玉杧产量、品质及改良土壤理化性质效果显著,红玉杧管理上可以适当增施这两种肥料。     

减量化肥配施叶面肥对山核桃产量及品质的影响

为广西岩溶地区山核桃高质优产提供施肥理论依据,在广西环江县开展山核桃施肥试验。试验设置CK(常规施肥)、T1(80%常规施肥+尿素和磷酸二氢钾叶面肥)、T2(T1+微肥叶面肥)、T3(T2+氨基酸叶面肥)、T4(T2+腐殖酸叶面肥)、T5(T2+氨基酸叶面肥+腐殖酸叶面肥)6种施肥处理,对山核桃产量、品质、矿质元素含量及叶片氮磷钾养分进行分析。结果显示,不同施肥处理显著影响山核桃单果仁质量、出仁率和果壳厚度(P<0.05),其中,T4处理的单株产量、单果仁质量和出仁率为全组最高,分别较CK高出31.18%、17.29%和13.95%。不同施肥处理显著影响山核桃可溶性糖、单宁和脂肪含量(P<0.05),其中,T5处理的蛋白质、淀粉、脂肪含量均最高,分别较CK处理高出16.24%、6.43%、13.73%。对山核桃矿质元素含量研究的结果表明,喷施叶面肥对山核桃矿质元素含量有较明显的提升作用,除了T3处理的钙含量外,喷施叶面肥处理的矿质元素含量均高于CK。其中,T5处理的镁、锌、铁、硼和钙含量最高,分别较CK高出9.87%、39.34%、35.44%、18.10%和10.93%。综上,T4处理的山核桃产量最高,T5处理则是山核桃品质和矿质元素含量提升的最佳施肥方式,在广西岩溶地区山核桃生产中,可根据需求选择对应的叶面肥喷施方案。     

不同施肥处理对水稻生长及肥料利用率的影响

为研究不同施肥处理对水稻生长及肥料利用率的影响,设置常规施肥(CK1)、常规施肥无氮(F1)、常规施肥无磷(F2)、常规施肥无钾(F3)、配方施肥(CK2)、配方施肥无氮(Y1)、配方施肥无磷(Y2)、配方施肥无钾(Y3)8个处理,比较不同处理的水稻产量、农艺性状及氮、磷、钾肥利用率的差异,结果表明:CK2处理的株高、千粒重比CK1处理提高了8.11%、1.33%;CK2处理的667 m~2水稻产量最高,为493.2 kg;CK2处理的土壤碱解氮、有效磷、速效钾含量比CK1处理高4%、120%、19.42%;茎叶全氮、全磷、全钾含量高于籽粒含量,不同处理间籽粒和茎叶全氮、全磷、全钾含量差异较小;配方施肥的氮、磷、钾肥利用率比常规施肥分别提高了3.76%、1.10%、4.93%。     

水肥一体化对生姜生长及叶片CO2、H2O交换特性的影响

以“莱芜大姜”为试材,研究了等量施肥条件下,沟灌常规施肥(CK)、滴灌常规施肥(T1)、水肥一体化(T2)对生姜生长,叶片H2O、CO2交换参数等的影响.结果表明,不同处理生姜地上部茎叶干物质量无显著差异,但T1、T2处理的地下根茎干物质量分别较CK增加11.15％和16.95％.水肥一体化可显著提高生姜叶片色素含量和净光合速率(Pn),降低蒸腾速率(Tr),提高水分利用效率(WUE).生姜根茎膨大期(9月16日),T1、T2处理叶片叶绿素含量和Pn分别比CK高6.77％、8.99％和10.21％、16.23％;生姜发棵期(8月20日),T1、T2处理叶片的Tr分别比CK低10.19％和9.42％;T1、T2处理的WUE无显著差异,但显著高于CK,8月26日9:00达峰值时,T1、T2的WUE分别比CK高23.83％和28.74％.T1、T2处理的灌溉水生产效率分别比CK高132.06％和146.79％;肥料偏生产力分别高12.54％和17.94％.     

不同施肥水平对温室番茄生长、氮吸收及产量品质的影响

以温室番茄为研究对象,基于水肥一体化技术研究了5种施肥水平(以N计,N0:0 kg/hm~2、N1:150kg/hm~2、N2:300 kg/hm~2、N3:450 kg/hm~2、N4:600 kg/hm~2,N-P-K=15-5-25)下番茄生长和氮素养分累积动态变化,探究水肥一体化技术下不同施肥水平对番茄生长发育、氮吸收及肥料利用率的影响。结果表明:N2处理下的番茄植株呈矮壮化生长,株高较N4处理下降15.9%(P0.05),茎粗较N4处理增加27.8%(P0.05)。N2处理具有较高的叶片SPAD值,其在番茄定植后55与115 d时较N4处理分别增加10.7%和13.2%(P0.05)。随生育期推进,番茄植株地上部干物质量与氮累积量增加呈"慢-快-慢"的趋势,提高施肥水平可增加番茄植株地上部干物质量与氮累积量,但施肥处理间并无显著性差异。果实品质受到施肥的显著影响,其中N2处理的可溶性固形物较N0处理增加28.3%(P0.05),可滴定酸含量比处理N0和N4分别增加22.5%和19.8%(P0.05)。施肥增加了番茄产量,但施肥水平过高对产量并无显著提升,其中N2处理产量较N0处理增加了13.2%,且与处理N3、N4相比无显著差异。温室番茄的氮素利用效率(NUE)和肥料偏生产力(PFP)均随施肥水平升高而显著下降,N2处理的NUE和PEP分别为N4处理的1.82和1.74倍(P0.05),N2处理下温室番茄的氮肥农学利用率最高,为N3、N4处理的1.9和2.9倍(P0.05)。综合考虑番茄生长、产量品质及肥料利用率等指标,本试验条件下,N2施肥水平为供试水肥一体化条件下的适宜肥料用量。     

有机无机复混肥对花生生长和品质的影响

试验以不施肥(CK)为对照处理,在同等施肥量下设置化肥处理(NPK)、有机无机复混肥处理(T1和T2),研究其对土壤养分含量、花生农艺性状和花生产量、品质指标的影响。结果表明:与CK相比,化肥处理(NPK)和有机无机复混肥处理均促进了花生生长,增加了土壤速效养分含量,且NPK、T1和T2分别增产9.5%、17.3%和19.7%;与单施化肥处理相比,有机无机复混肥处理改良了土壤pH,提高了土壤速效钾含量,明显改善花生农艺性状,T1和T2处理分别增产7.1%和9.3%,分别提高肥料偏生产力21.0%和23.5%、肥料贡献率6.0%和7.8%。因此,在等量施肥下,有机无机复混肥对土壤速效养分含量的增加、花生农艺性状的改善以及产量的提升具有更好的促进作用,肥料的偏生产力和肥料贡献率更高,是未来花生可持续生产的重要施肥措施。     

水肥一体化减量施肥对芒果产量、品质及肥耗的影响

为探究芒果水肥一体化条件下最佳施肥量,在昌江农场以红玉芒为试材,研究了在常规沟施化肥(CK),水肥一体化等量施肥(T1)、减量10%(T2)、减量20%(T3)、减量30%(T4)、减量40%(T5)施肥对芒果产量、品质及肥耗的影响。结果表明,各处理产量之间无显著性差异(P0.05)。与CK相比,T4、T5处理肥料产出率显著提升(P0.05)。各减量施肥对芒果的生物学性状略有影响,随着施肥量降低,芒果果实横径显著增加;芒果果实果长、果宽及品质无显著差异。对芒果经济性状的分析,各水肥处理的经济效益均高于CK,其中T2处理经济效益最高,达到了324 566.5元/hm~2,较CK增幅达15.23%。通过对果实品质以及产量的主成分评价,果实各指标的主成分打分由高到低排列依次为T3T4T2CKT5T1。因此,在水肥一体化条件下,90%常规施肥量经济效益最高;在常规施肥量减少40%的水肥一体化条件下,肥料的产出率最高,肥耗最低且不会降低果实产量和品质;在常规施肥量减少20%水肥一体化条件下,芒果的各项品质指标及产量综合得分最高。     

低氮和干旱胁迫对富士和秦冠生长及氮素利用的影响

【目的】以富士（Fuji）、 秦冠（Qinguan）嫁接在平邑甜茶（Malus hupehensis Rehd.）上的当年生盆栽苗为试验材料,采用砂培方法,研究了缺氮胁迫和干旱对富士和秦冠生长情况、 光合参数、 植株各部位氮磷钾含量及氮素利用效率的影响,分析比较了低氮干旱条件下富士和秦冠生长及氮素利用的差异,以期为果树生产高效肥水利用提供理论指导。【方法】试验共设四个处理: 正常氮正常水（ZZ）、 低氮正常水（DZ）、 正常氮干旱（ZG）、 低氮干旱（DG）。氮素和水分均设置两个水平,分别为正常氮（6 mmol/L NO-3-N）、 低氮（0.3 mmol/LNO-3-N）、 正常供水（保持盆中砂子相对含水量为饱和含水量的80%~85%）、 干旱处理（保持盆中砂子相对含水量为饱和含水量的60%~65%）。【结果】富士和秦冠的生物量（茎和叶）、 株高茎粗等生长指标以及光合速率、 气孔导度、 蒸腾速率均为正常氮正常水（ZZ）＞低氮正常水（DZ）＞正常氮干旱（ZG）＞低氮干旱（DG）,并且相对应处理下秦冠的以上指标均高于富士;正常供水下,缺氮处理使富士、 秦冠的根冠比比正常氮处理均有所增加,富士提高了2.05%,秦冠提高了22.40%。富士和秦冠的氮、 磷、 钾含量均表现出正常氮正常水（ZZ）＞低氮正常水（DZ）＞正常氮干旱（ZG）＞低氮干旱（DG）; 氮、 钾元素含量在植株各部位的分布顺序依次是叶＞根＞茎,磷元素则是根＞叶＞茎;光合氮素利用效率（PNUE）和氮素利用效率表现为秦冠处理之间差异极显著,富士处理之间差异不显著;秦冠的PNUE和NUE明显高于富士,在低氮正常水（DZ）处理下,秦冠氮肥利用率比富士高42.07%,在低氮干旱（DG）处理下高64.14%;低氮胁迫下富士和秦冠的NUE显著提高,并且秦冠提高的幅度高于富士。【结论】施用氮肥能够显著提高富士与秦冠的干物质量,同等水肥条件下,秦冠生长优于富士;水分亏缺会减少叶片对氮的吸收,干旱条件下适度增施氮肥,可提高果树的抗旱能力;低氮干旱胁迫下秦冠的生长指标、 光合指标及氮素利用效率指标均优于富士,表现出较强的抗低氮干旱胁迫的能力。     

Pasture Vegetation Elemental Analysis by Laser-Induced Breakdown Spectroscopy

Laser-induced breakdown spectroscopy (LIBS) is a new technique for the analysis of plant material. This study investigates the application of LIBS to pasture-based plant samples. The LIBS measurements were obtained from pelletized pasture samples (100 samples) that had been also analyzed by inductively coupled plasma–optical emission spectroscopy (ICP-OES) following microwave digestion for calibration and comparison purposes. Comparisons for elements sodium (Na), potassium (K), magnesium (Mg), calcium (Ca), manganese (Mn), iron (Fe), copper (Cu), zinc (Zn), boron (B), phosphorus (P), and sulfur (S) showed that LIBS could be used for almost all the standard profile total elements with concentrations down to low mg/kg levels (observed error of Na: 0.024 percent, K: 0.18 percent, Mg: 0.016 percent, Ca: 0.073 percent, P: 0.017 percent, Mn: 31 mg/kg, Fe: 150 mg/kg, Zn: 6.6 mg/kg, and B: 1.1 mg/kg). Elemental analysis at less than mg/kg levels was not possible using LIBS. The elements S and Cu were particularly difficult to analyze with reliability using LIBS at the concentration levels found in the plant samples. Replacing microwave digestion and subsequent ICP analysis with a direct analysis of dried plant samples using LIBS has the potential to improve the productivity and reduce the cost of testing.     

Faculty positions:Center for Agricultural Resources Research,Chinese Academy of Sciences

正The Center for Agricultural Resources Research(CARR),the Institute of Genetics and Developmental Biology(IGDB),Chinese Academy of Sciences,invites applicants for several research group leader positions.CARR is one of the research organizations in Chinese Academy of Sciences(CAS).We seek nominations and applications from individuals who have expertise and a record of accomplishment in research areas related to ecology,agro-hydrology,     

Macroinvertebrates in North American tallgrass prairie soils: effects of fire, mowing, and fertilization on density and biomass

The responses of tallgrass prairie plant communities and ecosystem processes to fire and grazing are well characterized. However, responses of invertebrate consumer groups, and particularly soil-dwelling organisms, to these disturbances are not well known. At Konza Prairie Biological Station, we sampled soil macroinvertebrates in 1994 and 1999 as part of a long-term experiment designed to examine the effects and interactions of annual fire, mowing, and fertilization (N and P) on prairie soil communities and processes. For nearly all taxa, in both years, responses were characterized by significant treatment interactions, but some general patterns were evident. Introduced European earthworms (Aporrectodea spp. and Octolasion spp.) were most abundant in plots where fire was excluded, and the proportion of the total earthworm community consisting of introduced earthworms was greater in unburned, unmowed, and fertilized plots. Nymphs of two Cicada genera were collected (Cicadetta spp. and Tibicen spp.). Cicadetta nymphs were more abundant in burned plots, but mowing reduced their abundance. Tibicen nymphs were collected almost exclusively from unburned plots. Treatment effects on herbivorous beetle larvae (Scarabaeidae, Elateridae, and Curculionidae) were variable, but nutrient additions (N or P) usually resulted in greater densities, whereas mowing usually resulted in lower densities. Our results suggest that departures from historical disturbance regimes (i.e. frequent fire and grazing) may render soils more susceptible to increased numbers of European earthworms, and that interactions between fire, aboveground biomass removal, and vegetation responses affect the structure and composition of invertebrate communities in tallgrass prairie soils.     

Assessing the effectiveness of conservation measures: Resolving the “wicked” problem of the Steller sea lion

“Wicked” problems are those that are complex and that change when solutions are applied. Many conflicts in conservation fall into this category. The study approached the problem of how to constrain the apparent wickedness of a problem in the conservation management of a species by using simple empirical indicators to carry out iterative assessment of the risk to a population and to document how this risk evolves in relation to the addition of new data and the implementation of management actions. Effects of high levels of uncertainty within data and also concerning population structure were examined through stochastic simulation and by exploration of scenarios. Historical trends in the example used, the Steller sea lion, showed rapid declines in abundance in some regions during the 1980s. The current total population is 130,000-150,000 Steller sea lions through Alaska and British Columbia and this number has been stable since about 1990 in spite of regional differences in population dynamics. Regional differences in the sequence of changes in the number of pups and non-pups, suggested that an internal re-distribution of juveniles could have happened between 1980 and 1990. Current productivity also appears close to the long-term mean. Stochastic population projection using various scenarios showed that, based upon this history, the risk of extinction for the population has declined and is below reasonable thresholds for considering the population to be endangered. The trends in risk suggest that management actions taken since 1990 have probably been effective. Consequently, the conservation management objectives for the Steller sea lion are probably being met. The approach provides a mechanism, based upon experience and scenario analysis, for exploring future policy options and may help to constrain the debate amongst stakeholders about the cost-benefit trade-offs associated with different options.     

Soil-profile distribution of primary and secondary plant-available nutrients under conventional and no tillage

Nutrient distributions under no tillage (NT) compared with conventional disk-and-bed tillage (CT) management in the warm, humid region of the southeastern USA need to be assessed so that future placement, quantity, and type of fertilizers can be altered, if necessary, to efficiently match crop demands. We determined soil-profile distributions of pH, N, P, S, K, Ca, Mg, Na, Zn, Fe, Mn, and Cu to a depth of 0.9 m at the end of 8.5 years of continuous CT and NT management on a Weswood silty clay loam (fine, mixed, thermic Fluventic Ustochrept) in southcentral Texas. Most dramatic changes occurred within the 0–0.05 m depth, where soil under NT had lower pH, Fe, and Cu than under CT, but greater P, K, Zn, and Mn. Greater P and K under NT than under CT also occurred below the till-zone (0.15–0.3 m). At a depth of 0–0.3 m, soil under NT contained greater amounts of extractable P, K, Zn, Fe, Mn, and Cu than under CT. Nitrogen fertilization had little effect on nutrient distributions, except resulting in greater extractable K at 0–0.05 m and greater nitrate at 0–0.15 m. Few changes in soil-profile distributions were observed for extractable S, Ca, Mg, and Na. Long-term continuous use of NT on this fine-textured, high-fertility (except for N) soil had no apparent adverse effects on nutrient distributions relative to CT, but enhanced conservation and availability of P, K, Zn, Fe, Mn, and Cu near the soil surface where crop roots proliferate.     

Variation in quality parameters between and within 14 Nordic tree fruit and berry species

Abstract

A 3-year study was carried out to investigate quality parameters in 14 tree fruit and berry species grown in southern Norway. The species were blueberry, apple, aronia, sour cherry, sweet cherry, red raspberry, strawberry, blackcurrant, gooseberry, red currant and elderberry, harvested along with wild bilberry, cloudberry and lingonberry. Significant differences between species were identified for all quality parameters. The coefficient of variation between species was lowest for pH (12.5%), dry matter (18.9%) and soluble solids (25.3%), followed by titratable acids (59.3%), total phenolics (83.8%), antioxidant capacity FRAP (85.7%) and antiradical power by the DPPH-assay (97.8%), total monomeric anthocyanins (132%) and ascorbic acid (137%). Average coefficient of variation within species were lower and ranged from 4 (pH) to 62% (ascorbic acid). Only the FRAP values were significantly affected by harvesting year with lower levels in 2004 than in 2005 and 2006. There were significant interactions between species and harvesting year for dry matter, soluble solids, pH, ascorbic acid and FRAP. The results indicate generic ranges in composition within species independent upon growing location and climate, and the composition of the tree fruits and berries is not likely to deviate from these ranges. It is concluded that desirable composition of tree fruits and berries and their products should primarily be achieved by selection among species rather than searching fors broadened variation within individual species.     

Potassium Fixation and Release Characteristics in Rhizosphere and Nonrhizosphere Soils for a Rapeseed–Rice Cropping Sequence

Potassium (K) fixation and release in soil are important factors in the long-term sustainability of a cropping system. Changes in K concentration and characteristics of K fixation and release in rhizosphere and nonrhizosphere soils in the rapeseed (Brassica napus L.)–rice (Oryza sativa L.) rotation were investigated using a rhizobox system. The concentrations of different forms of K in both rhizosphere and nonrhizosphere soils decreased with plants compared to without plants, regardless of K fertilizer application. Potassium uptake by crops mainly came from the rhizosphere soil. In the treatment without K fertilizer (–K), the main form of K supplied by the soil to the crops was 1.0 mol L^?1 nitric acid (HNO₃) nonextractable K, followed by nonexchangeable K, and then exchangeable K. In the treatment with K fertilizer (+K), the main K forms supplied by the soil to the crops were exchangeable K and nonexchangeable K. The amount and rate of K fixation after one cycle of the rapeseed–rice rotation was greater in rhizosphere soil than in nonrhizosphere soil. The amount and rate of K fixation of soil in the +K treatment were significantly less than in the –K treatment. The cumulative amounts of K released with 1.0 mol L^?1 ammonium acetate (NH₄OAc) and 1.0 mol L^?1 HNO₃ extraction increased with the increasing numbers of extractions, but the K-releasing power of soil by successive extraction decreased gradually and finally became almost constant. The release of K was less in rhizosphere soil than in nonrhizosphere soil. The release of K in the +K treatment was similar to that in the –K treatment in rhizosphere soil, but the K release in nonrhizosphere soil was greater with the +K than the –K treatment. Overall, the information obtained in this study will be helpful in formulating more precise K fertilizer recommendations for certain soils.     

Electron donor and pH relationships for biologically enhanced dissolution of chlorinated solvent DNAPL in groundwater

Biologically enhanced dissolution offers a method to speed removal of chlorinated solvent dense non-aqueous-phase liquid (DNAPL) sources such as tetrachloroethene (PCE) and trichoroethene (TCE) from aquifers. Bioremediation is accomplished by adding an electron donor to the source zone where fermentation to intermediates leading to acetic acid and hydrogen results. The hydrogen and possibly acetic acid are used by dehalogenating bacteria to convert PCE and TCE to ethene and hydrochloric acid. Reductive dehalogenation is thus an acid forming process, and sufficient alkalinity must be present to maintain a near neutral pH. The bicarbonate alkalinity required to maintain pH above 6.5 is a function of the electron donor: 800 mg/L of bicarbonate alkalinity is sufficient to achieve about 1.2 mM TCE dechlorination with glucose, 1.7 mM with lactate, and a much higher 3.3 mM with formate. Laboratory studies indicate that in mixed culture, formate can be used as an electron donor for complete conversion to ethene, contrary to pure cultures studies indicating it cannot. Various strategies can be used to add electron donor to an aquifer for DNAPL dehalogenation while minimizing pH problems and excessive electron donor usage, including use of injection-extraction wells, dual recirculation wells, and nested injection-extraction wells.     

Enhanced establishment and growth of giant cardon cactus in an eroded field in the Sonoran Desert using native legume trees as nurse plants aided by plant growth-promoting microorganisms and compost

To evaluate the feasibility of long-term desert reforestation technology of mixed vegetation, cardon cactus (Pachycereus pringlei) seedlings from indoor and outdoor nurseries were planted in the field adjacent to one seedling of potential legume nurse trees: mesquite amargo (Prosopis articulata), yellow palo verde (Parkinsonia microphylla), and blue palo verde (Parkinsonia florida). Some of the planting holes were also supplemented with common dairy compost. Additionally, the combinations of legume tree–cactus were inoculated with either a consortium of desert arbuscular mycorrhizal (AM) fungi, plant growth promoting bacteria (PGPB; the diazotroph Azospirillum brasilense Cd, and the phosphate solubilizer Paenibacillus sp.), or a mixture of all. The field experiments were evaluated periodically during 30 months for survival and growth. Cardons reared in an outdoor screen house survived better in the field than those reared in a controlled growth chamber and hardened later outdoors. Association with any legume nurse tree increased survival and enhanced growth of untreated cardons. For cardons growing alone, application of either compost, AM fungi, and all the treatments combined increased survival. For these plants, no treatment affected plant growth during the first 3 months after transplanting. Later, all treatments, except for AM fungi, enhanced plant growth. However, only 2 years after transplanting the enhanced growth effect of AM fungi was also significant. In the presence of the legume nurse trees, transient positive effects on cardon growth were recorded. General evaluation after 30 months of cultivation showed that the treatments positively affected cardon growth when growing alone or in combination only with mesquite amargo but not with the other two legume trees. This study proposes that young legume trees have the capacity to enhance survival and growth of cardon cactus, depending on the legume cactus combination. Additional treatments such as compost or PGPB can either amplify the effect or else attenuate it.