Tillage and the environment in sub-tropical Australia—Tradeoffs and challenges

Tillage is defined here in a broad sense, including disturbance of the soil and crop residues, wheel traffic and sowing opportunities. In sub-tropical, semi-arid cropping areas in Australia, tillage systems have evolved from intensively tilled bare fallow systems, with high soil losses, to reduced and no tillage systems. In recent years, the use of controlled traffic has also increased. These conservation tillage systems are successful in reducing water erosion of soil and sediment-bound chemicals. Control of runoff of dissolved nutrients and weakly sorbed chemicals is less certain. Adoption of new practices appears to have been related to practical and economic considerations, and proved to be more profitable after a considerable period of research and development. However there are still challenges. One challenge is to ensure that systems that reduce soil erosion, which may involve greater use of chemicals, do not degrade water quality in streams. Another challenge is to ensure that systems that improve water entry do not increase drainage below the crop root zone, which would increase the risk of salinity. Better understanding of how tillage practices influence soil hydrology, runoff and erosion processes should lead to better tillage systems and enable better management of risks to water quality and soil health. Finally, the need to determine the effectiveness of in-field management practices in achieving stream water quality targets in large, multi-land use catchments will challenge our current knowledge base and the tools available.     

Quantity and quality of organic inputs from coppicing leguminous trees influence abundance of soil macrofauna in maize crops in eastern Zambia

Soil invertebrates are the major determinants of soil processes such as organic matter decomposition and nutrient cycling. However, the effect of quantity and quality of organic inputs on soil biota has not been studied in agroforestry systems in southern Africa. Variations in soil macrofauna abundance under maize grown in fallows of Gliricidia sepium, Acacia anguistissima, Leucaena collinsii, Leucaena diversifolia, Leucaena esculenta, Leucaena pallida, Senna siamea, Calliandra calothyrsus and monoculture maize were assessed at three sites with contrasting agro-ecological conditions in eastern Zambia. It was hypothesised that spatial variations in soil macrofauna abundance under maize crops are mediated by heterogeneity in the quality and quantity of organic inputs produced by these legumes. The relationships between the abundance of macrofauna groups and litter, leaf, stump re-sprout and recycled biomass, stump survival and the quality index lignin (L)+polyphenol (P) to nitrogen (N) ratio were assessed using generalised linear models assuming spatial randomness (Poisson distribution) and aggregation (negative binomial distribution). Earthworms, beetles and millipedes showed spatial aggregation, which was partly explained by the heterogeneity in organic resource quantity and quality. Earthworms and beetles were more abundant under legumes that produced high quantities of biomass with low (L + P) to N ratios and species that have high stump survival after coppicing. Millipedes were favoured by species which produced high quantities of biomass with high (L + P) to N ratios. Although ants and termites showed spatial aggregation, their distributions were not influenced by the quantity or quality of biomass produced by the legumes. Centipedes and Arachnida showed spatial randomness, and their distribution was not influenced by any of the organic quality and quantity variables.     

基于灰色系统理论用机械特性指标预测苹果贮藏品质特性

研究了用机械特性指标测定和预测苹果贮藏品质的理论和方法。通过对冷藏条件下苹果理化特性与机械特性的连续测定，用灰色关联分析法研究了苹果理化特性与机械特性之间的关系，可知各理化特性指标对机械特性指标有不同程度的影响；用灰色系统理论的GM(1,5)模型建立了苹果品质多因子动态变化的数学模型，可确定苹果理化特性的各项指标对机械特性指标的影响与作用；用灰色系统理论的GM(1,2)模型确定了苹果机械特性与理化特性之间的关系，认为可用压缩时的最大力描述苹果的硬度、可溶性固形物、可滴定酸和水分，用压缩时的屈服力描述苹果的硬度、可滴定酸和水分，用弹性模量E0.5描述苹果的硬度；建立了灰色系统理论的预测模型GM(1,1)，在贮藏过程中，可用该模型预测苹果机械特性和理化特性动态变化的规律。通过验证，确定了预测模型的可用性。结果表明，用机械特性指标测定和预测苹果的贮藏品质是可行的，有一定的理论意义和实用价值。     

GISQ, a multifunctional indicator of soil quality

We present here an indicator of soil quality that evaluates soil ecosystem services through a set of 5 subindicators, and further combines them into a single general Indicator of Soil Quality (GISQ). We used information derived from 54 properties commonly used to describe the multifaceted aspects of soil quality. The design and calculation of the indicators were based on sequences of multivariate analyses. Subindicators evaluated the physical quality, chemical fertility, organic matter stocks, aggregation and morphology of the upper 5 cm of soil and the biodiversity of soil macrofauna. A GISQ combined the different subindicators providing a global assessment of soil quality.Research was conducted in two hillside regions of Colombia and Nicaragua, with similar types of land use and socio-economic context. However, soil and climatic conditions differed significantly. In Nicaragua, soil quality was assessed at 61 points regularly distributed 200 m apart on a regular grid across the landscape. In Colombia, 8 plots representing different types of land use were arbitrarily chosen in the landscape and intensively sampled. Indicators that were designed in the Nicaragua site were further applied to the Colombian site to test for their applicability.In Nicaragua, coffee plantations, fallows, pastures and forest had the highest values of GISQ (1.00; 0.80; 0.78 and 0.77, respectively) while maize crops and eroded soils (0.19 and 0.10) had the lowest values. Examination of subindicator values allowed the separate evaluation of different aspects of soil quality: subindicators of organic matter, aggregation and morphology and biodiversity of macrofauna had the maximum values in coffee plantations (0.89; 0.72 and 0.56, respectively on average) while eroded soils had the lowest values for these indicators (0.10; 0.31 and 0.33, respectively).Indicator formulae derived from information gained at the Nicaraguan sites were not applicable to the Colombian situation and site-specific constants were calculated.This indicator allows the evaluation of soil quality and facilitates the identification of problem areas through the individual values of each subindicator. It allows monitoring of change through time and can guide the implementation of soil restoration technologies. Although GISQ formulae computed on a set of data were only valid at a regional scale, the methodology used to create these indices can be applied everywhere.     

近红外光谱技术及其在农产品品质分析中的应用

近红外光谱技术是一种高效、快速的现代分析技术,已在很多领域得到广泛应用。文章对近红外光谱分析的技术原理、技术方法、技术特点作了简要介绍,并对其在农产品品质分析中的应用现状和应用前景进行了综述。     

基于激光图像的苹果品质分析与模型

该试验利用波长650 nm，功率25 mW的半导体激光及计算机视觉技术，初步探讨了激光图像的影响因素以及利用激光图像对苹果(嘎拉、红富士)品质进行无损检测的可行性。分别测定贮藏期间苹果的硬度、固酸比、果面底色、果型等品质指标，并获取图像参数及其像素个数(S1、S2、S3、S4)。试验结果显示，苹果的向阳面和背阳面对获取的激光图像的像素个数有显著的影响，而果型大小对其无显著影响。其中图像参数S3与各品质指标的皮尔逊相关系数最高。逐步回归表明，引入变量S3后模型的解释率最好(最高R²为0.99)，且都为极显著水平(P≤0.01)。试验的结果为利用小功率激光图像对苹果品质进行无损检测提供了理论依据。     

Relationships between sulfur concentration in mulberry Leaves and the quality of silkworm cocoon

A 40-day gnotobiotic microcosm experiment was carried out to quantify the effect of bacterial-feeding nematode on plat growth and nutrient absorption.The results showed that inoculation of bacterial-feeding nematode Protorhabditis sp.stimulated the growth of wheat (Triticum aestivum) and the uptake of N.By the end of the 40-day incubation wheat biomass and N uptake in the treatment with nematode and bacteria (Pseudomonas sp.)increased by 6.5% and 5.9%,respectively,compared with bacteria alone treatment.The presence of nematode mainly accelerated the growth of aboveground of wheat,while it slightly inhibited the root development.There was little difference in plant tissue N concentration between treatments.P concentration and uptake of wheat,however,were generally reduced by nematode, It appears that the enhancement of plant growth and nitrogen uptake is attributed to the enhancement of nitrogen mineraliztion induced by nematode feeding on bacteria,and the reduction of phosphorous uptake is the result of ewak root status and comptetition by bacteria immobilzation.     

亚热带湿润地区城市公园重建强度对其土壤酸化和土壤中重金属的影响

Soil quality is a major concern in the management of urban parks. In this study, the soils at 0–3, 3–13, and 13–23 cm depths were sampled from six urban parks, differing in reconstruction intensity(mainly changes made during conversion of natural forests into parklands), in the Pearl River Delta, China to determine how reconstruction intensity influenced the extent of acidification and heavy metal levels in the soils of urban parks in a humid subtropical environment. High reconstruction intensity(HRI) was practiced in three parks and low reconstruction intensity(LRI) in three other parks. The LRI soils were strongly to extremely acidic(with low exchangeable Ca, Mg, and K concentrations) while the HRI soils were much less acidic. Both total and extractable concentrations of soil heavy metals were related to the specific management practices and age of the park, but did not differ significantly between LRI and HRI parks or among soil depths. Soil p H was significantly related to soil exchangeable cation concentrations and base saturation but was weakly related or unrelated to soil heavy metal levels. Our results suggest that high intensity but not low intensity reconstruction significantly reduces the extent of soil acidification in the urban parks in a humid subtropical environment.     

不同温度对杏鲍菇减压贮藏品质的影响

为了研究减压贮藏条件下杏鲍菇的适宜贮藏温度,以杏鲍菇为试材,采用0.07 mm厚的低密度聚乙烯袋抽真空至0.06 MPa减压包装后,分别置于0、2、4、6和8℃下贮藏,研究了不同贮藏温度对减压贮藏条件下杏鲍菇的生理生化及品质的影响。结果表明:2、4℃较好地保持了杏鲍菇超氧化物歧化酶(superoxide dismutase,SOD)(P0.01)、过氧化氢酶(catalase,CAT)活性(P0.05),有效抑制了丙二醛(malondialdehyde,MDA)含量的上升(P0.01),降低了呼吸强度(P0.01),延缓了杏鲍菇子实体的衰老进程,较好地保持了杏鲍菇的硬度、弹性、内聚性和咀嚼性;降低了杏鲍菇的多酚氧化酶(polyphenol oxidase,PPO)活性(P0.01),有效抑制了杏鲍菇的褐变,较好地保持了杏鲍菇的色泽(P0.01)。因此,2~4℃为杏鲍菇减压贮藏条件下的适宜贮藏温度,有效延缓了杏鲍菇的后熟衰老进程,延长了杏鲍菇的贮藏期,从而为杏鲍菇的贮藏保鲜提供理论依据和技术方法。     

CO2浓度升高与增施钾肥对土壤化学性质的影响

采用土培和开顶箱法,研究了大气CO_2浓度升高与增施K肥共同作用对土壤化学性质的影响.结果表明,土壤中N、P的含量在高CO_2浓度和高K肥水平下下降,K的含量随K肥用量增加而增加.高K(200、300 mg/kg)处理和高浓度CO_2下温室次生盐渍化土壤中的NO_3~(-)、PO_4~(3-)、Ca~(2+)、Mg~(2+) 含量也显著降低.因此,在未来CO_2浓度升高的环境中,更多的K肥供应能促进作物对此生盐渍化土壤中养分的吸收,降低此生盐渍化土壤中盐分的积累.