The impact of cash cropping on shifting cultivation in Sabah,Malaysia

Pressure from the state government to abandon shifting cultivation and of the market to increase the production of cash crops are causing not simply a reduction in the practice of shifting cultivation in Sabah, Malaysia but marked alterations in the way many remote communities grow hill rice. Many traditional practices have been abandoned including the substitution of cash payments for community labour co-operation (gotong-royong), the use of traditional methods to monitor soil fertility such as maintaining fallow periods and the selection of appropriate hill rice varieties. The result has been a reduction in labour input, a shortage of land, continuous production, increased used of weedicides and a general failure to continue sustainable agricultural practices. Despite state incentives to abandon the practice the pressure to maintain real incomes among the rural communities has meant a continuation of the practice of shifting cultivation but under conditions which are now resulting in land degradation, slope instability and soil infertility.     

Reviews

Mason Durie Te Mana Te Kawanatanga: the politics of Maori self-determination Christopher Lingle Singapore’s authoritarian capitalism: Asian values, free market illusions and political dependency Roland J. L. Breton Atlas of the languages and ethnic communities of South Asia Lenore Manderson and Margerat Jolly (eds) Sites of desire, economies of pleasure: sexualities in Asia and the Pacific Eric Venbrux A Death in the TWI Islands: conflict, ritual and social life in an Australian community Brij V. Lal A vision for change     

Target the core: durable plant resistance against filamentous plant pathogens through effector recognition

Plant pathogens colonize their host through the secretion of effector proteins that modulate plant metabolism and immune responses to their benefit. Plants evolve towards effector recognition, leading to host immunity. Typically, pathogen effectors are targets for recognition through plant receptors that are encoded by resistance genes. Resistance gene mediated crop immunity puts a tremendous pressure on pathogens to adapt and alter their effector repertoire to overcome recognition. We argue that the type of effector that is recognized by the host may have considerable implications on the durability of resistance against filamentous plant pathogens. Effector genes that are conserved among pathogens and reside in core genome regions are most likely to hold indispensable virulence functions. Consequently, the cost for the pathogen to overcome recognition by the host is higher than for diversified, host‐specific effectors with a quantitative impact on virulence. Consequently, resistance genes that directly target conserved effector proteins without the interception of other effector proteins are potentially excellent resistance resources. © 2019 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.     

A simulation model assisted study on water and nitrogen dynamics and their effects on crop performance in the wheat-maize system: (II) model calibration, evaluation and simulated experimentation

The test on the model with data collected from two years’ field experiments revealed an ability to satisfactorily simulate crop parameters such as LAI, biomass accumulation and partitioning, yield, and variables influencing crop growth and development as nitrogen uptake by crops and partitioning in different organs, and dynamics of soil water and nitrogen including infiltration and leaching. With the model, crop yield, water use efficiency (WUE), nitrogen use efficiency (NYE) and water-nitrogen leaching at specific soil layers under various water and nitrogen management practices were simulated to provide data used as references for designing sustainable nitrogen and water management practices. The outputs of the simulated experiment with various treatments of irrigation and nitrogen application indicated that crop yield was closely related to water and nitrogen application, crop water use was positively related to irrigation amount, and nitrogen fertilization could improve the crop water use and WUE within certain limits. This is a valuable evidence to be considered in water-saving farming. Nitrogen uptake had a positive relation to nitrogen application, while irrigation to some extent improved its uptake by crops and hence increased NYE. Additionally, irrigation and fertilization had great effects on nitrogen leaching. Thus, in order to improve WUE and NYE, the model showed how nitrogen application and irrigation should be well coordinated.     

化感物质抑制连作黄瓜生长的作用机理

 苯丙烯酸、对羟基苯甲酸为黄瓜根系分泌物中的主要化感物质组分。通过模拟根系分泌物中的化感物质进行土培和水培试验,证明苯丙烯酸、对羟基苯甲酸对连作黄瓜根系生长有明显的抑制作用。在50～250μmol/L浓度范围内,随处理浓度的加大,抑制根系对K+、NO3、H2PO4吸收的作用显著,养分外渗速率加快,组织外渗相对电导率逐渐提高。苯丙烯酸、对羟基苯甲酸强烈地抑制黄瓜根系脱氢酶、根系结合ATP酶、硝酸还原酶、超氧化物歧化酶的活性,随理浓度的增大抑制作用增强。     

农业废弃物基生物炭的应用效应研究进展

生物炭因结构和理化性质独特、原材料丰富及应用前景广阔等特点,在农业及环境污染治理等领域的应用较为广泛。基于相关文献,综述了农业废弃物基生物炭在改善土壤理化性质、提高土壤养分、改善土壤微生态环境、促进作物生长、修复污染土壤及缓解连作障碍等方面的效应,旨在为农业废弃物基生物炭在农业生产中的应用提供参考。     

不同连作年限设施农用地土壤有机碳与细菌群落功能特征

为探明不同连作年限设施农用地土壤有机碳(Soil organic carbon, SOC)与细菌群落功能变化及其动态响应关系,以北京市南郊设施农业集中地为研究区,采用时空替代法系统分析了未种植(CK)、连作年限0～5年(0～5 a)、5～10年(5～10 a)、10～20年(10～20 a)和20年以上(20 a+)SOC、细菌群落结构及其代谢功能的变化。结合冗余分析(RDA)、典型相关分析(CCA)、PICRUSt2功能预测及Mantel test探究了SOC及其活性组分与细菌优势菌群的动态响应,以及与细菌代谢功能的相互关系。结果表明：连作使研究区微生物生物量碳(Microbial biomass carbon, MBC)、易氧化有机碳(Easily oxidizes organic carbon, EOC)、SOC含量及土壤有机碳密度(Soil organic carbon density, SOCD)均随种植年限先增后减,可溶性有机碳(Dissolved organic carbon, DOC)含量在20 a+时最高,微生物熵(Q)随连作年限增加而减小。连作降低了土壤细菌的多样性...     

南方农区草业在中国农业持续发展中的战略地位

在对中国南北自然资源优势进行广泛比较的基础上，通过生产调研和田间试验，剖析了农产品市场国际化后农业生产结构调整将面临的新问题，预示经济复苏后中国居民的食物消费结构将发生根本性转变。根据这些分析，提出发展南方农区草业是提高农业效益、增加农民收入、实现农业持续发展的有效途径。文章最后提出了南方农区草业的发展策略，并针对目前存在的问题，提出了一些可行的配套措施。     

氮肥对北疆滴灌复播青储玉米光合特性及养分利用的影响

为了解氮肥对北疆滴灌复播青储玉米生理指标的影响,提高氮肥利用效率,通过田间小区试验,研究了一管一行毛管布置模式下,不同氮肥处理（100、170、240、310、380 kg?hm －2）对复播青储玉米光合特性、土壤铵态氮分布的影响。结果表明,不同氮肥处理条件下复播玉米叶片净光合速率、蒸腾速率日变化曲线均呈单峰型;土壤铵态氮含量总体上随施氮量的增加先减少后增加;产量随施氮量的增加先增加后减小。综合分析认为,一管一行毛管布置模式下,240 kg?hm －2的施氮量处理下水氮耦合效果最佳,土壤铵态氮含量总体最少,产量与叶片水分利用效率最高,净光合速率较高。     

渭北旱塬麟游县种植业发展问题分析

根据渭北旱塬区麟游县的自然资源特点,在深入分析麟游县种植业现状的基础上,提出了麟游县种植业的发展对策:优化种植结构,发挥区域优势;退耕还林还草,改善生态环境;建立持续发展的种植业三元结构;改善种植业基本生产条件;完善社会化服务体系,促进种植业持续稳定发展。