保护性耕作及种植模式对蔬菜地耕层土壤CO2含量的影响

采用动态气室法分别对云南省通海县山地蔬菜地、长期连作蔬菜地及不同种植模式下的露地蔬菜地20 cm耕层土壤CO2含量进行田间直接测定,分析了不同保护性耕作措施及种植模式对土壤CO2含量的影响,同时分析了保护性耕作措施对蔬菜产量的影响。结果表明,以秸秆还田及有机物质增施为代表的保护性耕作措施能显著提高土壤CO2含量;秸秆覆盖和免耕相结合既有利于土壤呼吸产生CO2,又有利于蔬菜产量、产值提高,但免耕、深耕土壤CO2产生量无显著差异;增施有机物质总体上有利于蔬菜产量、产值提高,增施不同有机物质对蔬菜生产的影响顺序为烟杆>家禽、家畜粪便>废弃蔬菜叶>稻草,其中稻草对蔬菜具有较大的负面影响;土壤CO2含量与耕地利用情况密切相关,土壤CO2含量大小表现为水田>旱坡地;蔬菜-蔬菜连作>水稻/烤烟/玉米-蔬菜轮作;蔬菜-蔬菜连作地5年>10年>20年。

有机物质增施对蔬菜连作土壤肥力、盐碱化及CO_2含量的影响

[目的]了解不同有机物质增施对蔬菜连作地耕层土壤肥力、盐碱化、土壤CO2含量及蔬菜产量、产值的影响。[方法]于2008年11月至2009年6月,在云南通海县九街镇开展田间小区试验。[结果]结果表明,蔬菜连作种植造成了耕层土壤养分耗竭,地力衰退,土壤盐碱化;从连续3季蔬菜种植管理养分来说,有机物质增施有利于土壤养分含量提高,以满足作物对养分的需求,有机物质增施总体上促进耕层土壤pH值降低,从而有利于蔬菜连作土壤酸碱性改良,但耕层土壤Na+含量反而增加;动物粪肥增施有利于土壤CO2含量提高,从而促进土壤呼吸。不同有机物质增施对蔬菜生产的影响表现为烟杆>家禽、家畜粪便>废弃蔬菜叶>稻草,其中稻草对蔬菜具有较大的负面影响,有机物质增施总体上有利于蔬菜产量、产值提高;对连续3季蔬菜生产的影响表现为第3季蔬菜>第2季蔬菜>当季蔬菜。[结论]通过有机物质增施来培肥和改良土壤效果在短时间内不明显,尤其是稻草施用对当季蔬菜的生长反而有一定的负面效应,在蔬菜种植中应谨慎使用,从养分长期管理角度来说,有机物质增施有利于土壤养分含量的增加,改善蔬菜连作土壤生态环境,促进蔬菜健康生长,提高产量、产值。

保护性耕作对山地结球甘蓝生长和土壤CO_2含量的影响

为了解耕作措施对山地蔬菜种植的影响,改善山地土壤的生态环境,笔者通过田间小区试验研究了免耕及秸秆还田方式对山地土壤CO2含量及结球甘蓝的生长、发育和产量的影响。结果表明,秸秆覆盖和免耕相结合即有利于山地土壤呼吸产生CO2,又有利于山地蔬菜生长和产量、产值提高;免耕对土壤呼吸产生CO2影响不明显,但有利于蔬菜生长;深耕条件下增施秸秆,有利于土壤呼吸产生CO2,但对当季蔬菜的生长有一定的负面影响。

美国有关灌溉对根系及土壤呼吸影响的研究

在农业和生态系统研究中 ,对根系和土壤呼吸作用的评价日益重要 ,但人们关于土壤质地和土壤含水量对这些评价的影响了解甚少。通过研究柠檬近根区土壤干湿交替期间的土壤质地 ,以探索其对根系和土壤呼吸率以及土壤CO2 摩尔分数的影响。将试验作物分别种在砂质土、粉砂质土和黏质土中 ,测定根系和土壤呼吸率、土壤含水量、植株含水量和土壤CO2 摩尔分数等。结果发现 ,虽然不同土壤质地的植株—土壤—水分间的参数不同 ,但对植物的生长影响很小 ,在一般土壤湿度条件下 ,3种土壤质地的根土呼吸率基本相同 ,只有土壤表层释放的CO2 量随灌溉而不同 ,即由于砂壤土的多孔性 ,灌水后土壤CO2 释放量较多 ,而质地较密的另两种土壤CO2 摩尔分数较高。研究表明 ,土壤湿度的变化可以解释与CO2 释放量有关参数的变化原因 ,尤其在细颗粒土壤中。同时讨论了测定土壤CO2

Temporal Variations in Soil CO_2 Efflux Under Diferent Land Use Types in the Black Soil Zone of Northeast China

The quantification of soil CO2 effiux is crucial for better understanding the interactions between driving variables and C losses from black soils in Northeast China and for assessing the function of black soil as a net source or sink of atmospheric CO2 depending upon land use. This study investigated responses of soil CO2 effiux variability to soil temperature interactions with different soil moisture levels under various land use types including grassland, bare land, and arable （maize, soybean, and wheat） land in the black soil zone of Northeast China. The soil CO2 effiuxes with and without live roots, defined as the total CO2 efftux （FtS） and the root-free CO2 ei^lux （FrfS）, respectively, were measured from April 2009 to May 2010 using a static closed chamber technique with gas chromatography. The seasonal soil CO2 fluxes tended to increase from the beginning of the measurements until they peaked in summer and then declined afterwards. The mean seasonal FtS ranged from 20.3=h7.8 to 58.1~21.3 mg CO2-C m-2 h-1 for all land use types and decreased in the order of soybean land ~ grassland 〉 maize land ~ wheat land ） bare land, while the corresponding values of FrfS were relatively lower, ranging from 20.3~7.8 to 42.3~21.3 mg CO2-C m-2 h-1. The annual cumulative FtS was in the range of 107-315 g CO2-C m-2 across all land uses types. The seasonM CO2 effiuxes were significantly （P 〈： 0.001） sensitive to soil temperature at 10 cm depth and were responsible for up to 62% of the CO2 effiux variability. Correspondingly, the temperature coefficient Q10 values varied from 2.1 to 4.5 for the seasonal FtS and 2.2 to 3.9 for the FrfS during the growing season. Soil temperature interacting with soil moisture accounted for a significant fraction of the CO2 flux variability for FtS （up to 61%） and FrfS （up to 67%） via a well-defined multiple regression model, indicating that temperature sensitivity of C02 flux can be mediated by water availability, especially under water stress.

A Fuzzy Control Based Intelligent Control System for Flower Greenhouse

In order to realize intelligent control of flower greenhouse＇ s parameters of atmospheric temperature and humidity, lighting intensity, CO2 concentration and soil water content, it carries out design with ZigBee network, embedded controller and intelligent fuzzy control algorithm as core. With advantages of high precision and stability, the design of sensor circuit mainly employs digital module sensors. In order to save energy, the sensor circuit is controlled by relay switch to work at the proper time. The gateway node is designed by employing high performance 32-digit embedded controller and WinCE6.0 embedded OS is self customized. And embedded SQlite database is realized on WinCE6.0 for effectively managing data. The closed loop control is realized by employing fuzzy control algorithm and the test result shows that the deviation of atmospheric temperature is controlled within ± 0.5° C, the deviation of illumination intensity is controlled within ± 283 LUX, the deviation of CO2 concentration is controlled within ± 24 PPM, the deviation of atmospheric humidity is controlled within ± 13% and that of soil water content is controlled within ± 0.9%, thus all parameters fully meet practical requirements of flower greenhouse.

Salt Accumulation and Physiology of Naturally Occurring Grasses in Saline Soils in Australia

Salinity is a major soil contamination problem in Australia. To explore salinity remediation, we evaluated the concentrations of sodium （Na）, potassium （K）, magnesium （Mg）, and calcium （Ca） in roots and shoots and in the supporting soil of the naturally occurring grasses, Cynodon dactylon and Thinopyrurn ponticum, at two salt-affected sites, Gumble and Cundumbul in central-western New South Wales, Australia. The physiological parameters of the two grass species, including net photosynthetic rate （Pn）, stomatal conductance （gs）, and intercellular CO2 concentration （Ci）, were investigated using one mature leaf from C. dactylon and T. ponticum populations. Increasing salinity levels in the topsoil had a significant influence on Ci and gs, whereas no significant effect occurred on Pn in C. dactylon and T. ponticum. The Pn values in C. dactylon and T. ponticum were greater at Cundumbul than at Gumble. The greater Mg concentration facilitated greater Pn in C. dactylon and T. ponticum populations at Cundumbul than Gumble. With increasing salinity levels in the soil, Na accumulation increased in C. dactylon and T. ponticum. The ratio between K and Na was ~ 1 in roots and shoots of both populations irrespective of the sites. Bioaccumulation factor （BF） and translocation factor （TF） results revealed that K and Na translocations were significantly higher in T. ponticum than in C. dactylon, whereas Ca and Mg translocations were significantly higher in C. dactylon than in T. ponticum. Accumulation of Na, K, Mg, and Ca ions was higher in T. ponticum than in C. dactylon; therefore, we suggest that T. ponticum as a greater salt accumulator than C. dactylon could be used for revegetation and phytoremediation of the salt-affected soils.

Carbon Dioxide and Nitrous Oxide Emissions from Naturally Occurring Sulfate-Based Saline Soils at Different Moisture Contents

Soil salinization may negatively affect microbial processes related to carbon dioxide （CO2） and nitrous oxide （N20） emissions. A short-term laboratory incubation experiment was conducted to investigate the effects of soil electrical conductivity （EC） and moisture content on CO2 and N20 emissions from sulfate-based natural saline soils. Three separate 100-m long transects were established along the salinity gradient on a salt-affected agricultural field at Mooreton, North Dakota, USA. Surface soils were collected from four equally spaced sampling positions within each transect, at the depths of 0-15 and 15-30 cm. In the laboratory, artificial soil cores were formed combining soils from both the depths in each transect, and incubated at 60% and 90% water-filled pore space （WFPS） at 25 ~C. The measured depth-weighted EC of the saturated paste extract （ECe） across the sampling positions ranged from 0.43 to 4.65 dS m-1. Potential nitrogen （N） mineralization rate and CO2 emissions decreased with increasing soil ECe, but the relative decline in soil CO2 emissions with increasing ECe was smaller at 60% WFPS than at 90% WFPS. At 60% WFPS, soil N20 emissions decreased from 133 g N20-N kg-1 soil at ECe （ 0.50 dS m-1 to 72 μg N20-N kg-1 soil at ECe = 4.65 dS m-1. In contrast, at 90% WFPS, soil N20 emissions increased from 262 g N20-N kg-1 soil at ECe ： 0.81 dS m-1 to 849 g N20-N kg-1 soil at ECe ： 4.65 dS m-1, suggesting that N20 emissions were linked to both soil ECe and moisture content. Therefore, spatial variability in soil ECe and pattern of rainfall over the season need to be considered when up-scaling N20 and CO2 emissions from field to landscape scales.

Carbon Mineralization and Microbial Attributes in Straw-Amended Soils as Affected by Moisture Levels

An 80-d incubation experiment was conducted to investigate straw decomposition, the priming effect and microbial characteristics in a non-fertilized soil （soil 1） and a long-term organic manure-fertilized soil （soil 2） with and without 13C-labeled maize straw amendment under different moisture levels. The soil 2 showed a markedly higher priming effect, microbial biomass C （Cmic）, and β-glucosidase activity, and more abundant populations of bacteria and fungi than the soil 1. Also, soil CO2 emission, Cmic, /3- glucosidase activity, and bacterial and fungal population sizes were substantially enhanced by straw amendment. In the presence of straw, the amount of straw mineralization and assimilation by microbes in the soil at 55% of water holding capacity （WHC） were significantly higher by 31% and 17%, respectively, compared to those at 25% of WHC. In contrast, β-glucosidase activity and fungal population size were both enhanced as the moisture content decreased. Cmic decreased as straw availability decreased, which was mainly attributed to the reduction of straw-derived Cmic. Amended soils, except the amended soil 2 at 25% of WHC, had a more abundant fungal population as straw availability decreased, indicating that fungal decomposability of added straw was independent of straw availability. Non-metric multidimensional scaling analysis based on fungal denatured gradient gel electrophoresis band patterns showed that shifts in the fungal community structure occurred as water and straw availability varied. The results indirectly suggest that soil fungi are able to adjust their degradation activity to water and straw availability by regulating their community structure.