Incentive for shifts in water management systems by shrimp culturists in southern Thailand

ABSTRACT:   Water management systems and other business situations of shrimp culturists were surveyed in two districts in southern Thailand. There were three types of water management systems in southern Thailand, namely closed, semiclosed and open systems, categorized by the frequency of exchange of pond water. Shrimp culturists in those districts tended to shift their system from the open system to the closed system of their own accord, and the average net income ratio decreased due to the change of water management system in a district from more than 2 to less than 1. The reason for this shift, in spite of the decrease in the profit rate, was prevention of infectious disease caused by water exchange. In conclusion, it was proven that independent shrimp culturists, such as medium and small scale shrimp pond owners in southern Thailand, would accept short-term decreases in profit rate in order to stabilize production.     

Management of Meloidogyne incognita in yam-based cropping systems with cover crops

The effect of intercropping cover crops was with yam was assessed for nematode management both in pot and field conditions in Nigeria. The cover crops were sown with yams in pots containing sterile soil and inoculated with 5000 eggs of Meloidogyne incognita. In the field, each cover crop was separately intercropped with yams inoculated with 10,000 nematodes. From both pot and field experiments, no nematode damage was observed on yam tubers that were intercropped with Aeschynomene histrix, Crotolaria juncea, and Tagetes erecta. Damage in intercropped tubers was reduced by 72.7% with Mucuna pruriens, Centrosema pubescens, and Pueraria phaseoloides and by 58.3% with Stylosanthes guianensis compared to yams planted without cover crops; they also had lower (p ≤ 0.05) nematode populations. Cajanus cajan, Lablab purpureus and Vigna unguiculata however, supported high nematode populations and led to nematode damage in intercropped yams. Tubers from M. incognita-inoculated plants were more damaged and lost 42% more weight (p ≤ 0.05) following three months of storage than tubers from uninoculated plants. Intercropping yams with selected cover crops can be useful in managing M. incognita without reducing yam yields.     

Effects of mechanical and chemical methods on weed control,weed seed rain and crop yield in maize,sunflower and soyabean

Eight field experiments with maize (Zea mays L.), sunflower (Helianthus annuus L.) and soyabean (Glycine max (L.) Merr.) were carried out in central Italy in order to evaluate the effects of mechanical and chemical methods (spring-tine harrowing, hoeing, hoeing-ridging, split-hoeing, finger-weeding, herbicides in the row + inter-row hoeing, herbicides broadcast) on weed control, weed seed rain and crop yield. The choice of chemical and mechanical treatments in maize and soyabean compared to sunflower, required to be managed more carefully in order to maximize the weed control reducing yield losses. A global rating of weed control methods, based on their weed control efficacy, was obtained as useful means to assist farmers and technicians to choose the more appropriate weed control method. The combination of herbicides intra-row and hoeing inter-row gave best efficacy (on average 99% of weed control), with a 50% reduction in the chemical load in the environment. Hoeing-ridging gave good results, both inter- and intra-row (on average 93% of weed control); this method was also effective in reducing competitive ability and seed production of uncontrolled weeds. Split-hoeing or finger-weeding showed some limitations giving satisfactory results only when combined. Harrowing gave lowest weed control, although when combined to other mechanical methods, can help achieve a better efficacy.     

新形势下农业科研单位干部人事档案管理现状与对策

分析新形势下农业科研单位干部人事档案管理的现状,提出应对措施,强化干部人事档案管理,为单位人力资源开发提供完整的人才信息保障。     

Reduced tillage with residue retention improves soil labile carbon pools and carbon lability and management indices in a seven-year trial with wheat-mung bean-rice rotation

Soil total organic carbon (TOC) is a composite indicator of soil quality with implications for crop production and the regulation of soil ecosystem services. Research reports on the dynamics of TOC as a consequence of soil management practices in subtropical climatic conditions, where microbial carbon (C) loss is high, are very limited. The objective of our study was to evaluate the impact of seven years of continuous tillage and residue management on soil TOC dynamics (quantitative and qualitative) with respect to lability and stratification under an annual wheat-mung bean-rice cropping sequence. Composite soil samples were collected at 0-15 and 15-30 cm depths from a three-replicate split-plot experiment with tillage treatment as the main plots and crop residue levels as the sub-plots. The tillage treatments included conventional tillage (CT) and strip tillage (ST). Residue levels were high residue level (HR), 30% of the plant height, and low residue level (LR), 15%. In addition to TOC, soil samples were analyzed for particulate organic C (POC), permanganate oxidizable C (POXC), basal respiration (BR), specific maintenance respiration rate (qCO₂), microbial biomass C (MBC), potentially mineralizable C (PMC), and TOC lability and management indices. The ST treatment significantly increased the TOC and labile C pools at both depths compared with the CT treatment, with the effect being more pronounced in the surface layer. The HR treatment increased TOC and labile C pools compared with the LR treatment. The ST + HR treatment showed significant increases in MBC, metabolic quotient (qR), C pool index (CPI), C lability index (CL_I), and C management index (CMI), indicating improved and efficient soil biological activities in such systems compared with the CT treatment. Similarly, the stratification values, a measure of soil quality improvement, for POC and MBC were > 2, indicating improved soil quality in the ST + HR treatment compared with the CT treatment. The ST + HR treatment not only significantly increased the contents of TOC pools, but also their stocks. The CMI was correlated with qCO₂, BR, and MBC, suggesting that these are sensitive indicators of early changes in TOC. The qCO₂ was significantly higher in the CT + LR treatment and negatively correlated with MBC and CMI, indicating a biologically stressed soil condition in this treatment. Our findings highlight that medium-term reduced tillage with HR management has profound consequences on soil TOC quality and dynamics as mediated by alterations in labile C pools.     

Spectral indices measured with proximal sensing using canopy reflectance sensor, chlorophyll meter and leaf color chart for in-season grain yield prediction of basmati rice

A number of optical sensing tools are now available and can potentially be used for refining need-based fertilizer nitrogen (N) topdressing decisions. Algorithms for estimating field-specific fertilizer N needs are based on predictions of yield made while the crops are still growing in the field. The present study was conducted to establish and validate yield prediction models using spectral indices measured with proximal sensing using GreenSeeker canopy reflectance sensor, soil and plant analyzer development (SPAD) chlorophyll meter, and two different types of leaf color charts (LCCs) for five basmati rice genotypes across different growth stages. Regression analysis was performed using normalized difference vegetation index (NDVI) recorded with GreenSeeker sensor and leaf greenness indices measured with SPAD meter and LCCs developed by Punjab Agricultural University, Ludhiana (India) (PAU-LCC) and the International Rice Research Institute, Philippines (IRRI-LCC). The exponential relationship between NDVI and grain yield exhibited the highest coefficient of determination (R²) and minimum normalized root mean square error (NRMSE) at panicle initiation stage and explained 38.3%-76.4% variation in yield using genotype-specific models. Spectral indices pooled for different genotypes were closely related to grain yield at all growth stages and explained 53.4%-57.2% variation in grain yield. Normalizing different spectral indices with cumulative growing degree days (CGDD) decreased the accuracy of yield prediction. Normalization with days after transplanting (DAT), however, did not reduce or improve the predictability of yield. The ability of each model to predict grain yield was validated with an independent dataset collected from two experiments conducted at different sites with a range of fertilizer N doses. The NDVI-based genotype-specific models exhibited a robust linear correlation (R²=0.77, NRMSE=7.37%, n=180) between observed and predicted grain yields only at 35 DAT (i.e., panicle initiation stage), while the SPAD, PAU-LCC, and IRRI-LCC consistently provided reliable predictions (with respective R² of 0.63, 0.60, and 0.53 and NRMSE of 10%, 10%, and 13.6%) even with genotype invariant models with 900 data points obtained at different growth stages. The study revealed that unnormalized values of spectral indices, namely NDVI, SPAD, PAU-LCC, and IRRI-LCC, can be satisfactorily used for in-season estimation of grain yield for basmati rice. As LCCs are very economical compared with chlorophyll meters and canopy reflectance sensors, they can be preferably used by small farmers in developing countries.     

Conservation management decreases surface runoff and soil erosion

Conservation management practices – including agroforestry, cover cropping, no-till, reduced tillage, and residue return – have been applied for decades to control surface runoff and soil erosion, yet results have not been integrated and evaluated across cropping systems. In this study we collected data comparing agricultural production with and without conservation management strategies. We used a bootstrap resampling analysis to explore interactions between practice type, soil texture, surface runoff, and soil erosion. We then used a correlation analysis to relate changes in surface runoff and soil erosion to 13 other soil health and agronomic indicators, including soil organic carbon, soil aggregation, infiltration, porosity, subsurface leaching, and cash crop yield. Across all conservation management practices, surface runoff and erosion had respective mean decreases of 67% and 80% compared with controls. Use of cover cropping provided the largest decreases in erosion and surface runoff, thus emphasizing the importance of maintaining continuous vegetative cover on soils. Coarse- and medium-textured soils had greater decreases in both erosion and runoff than fine-textured soils. Changes in surface runoff and soil erosion under conservation management were highly correlated with soil organic carbon, aggregation, porosity, infiltration, leaching, and yield, showing that conservation practices help drive important interactions between these different facets of soil health. This study offers the first large-scale comparison of how different conservation agriculture practices reduce surface runoff and soil erosion, and at the same time provides new insight into how these interactions influence the improvement or loss of soil health.     

土壤有机碳组分和微生物群落对有机管理的响应

土壤有机碳（soil organic carbon, SOC）和微生物是土壤质量和健康变化的重要评价指标。为了探究热区不同的管理方式对茶园土壤有机碳组分和微生物群落组成的影响,本研究选取海南省白沙县有机茶园（organic tea plantations, OTP）和常规茶园（conventional tea plantations, CTP）作为研究对象,利用¹³C-核磁共振（¹³C-NMR）生物标记技术和磷脂脂肪酸（PLFA）来研究不同管理模式下茶园土壤中有机碳化学组分和土壤微生物的群落组成的变化,明确有机管理和无机管理对土壤有机碳组分（烷基C、O-烷基C、芳香C和羧基C）和微生物群落组成的影响。结果显示：（1）与无机管理相比,有机管理显著改变了茶园土壤中养分含量。有机质（SOM）含量增加了47.86%,总氮（TN）和总磷（TP）含量分别增加了37.40%和100%（P<0.05）。硝态氮（NO₃^--N）含量显著增加了78.80%（P<0.05）,总钾（TK）和速效钾（AK）含量显著降低（P<0.05）。（2）有机管理增加了茶园土壤中烷基C和O-烷基C的相对含量。同时,脂肪族C/芳香C的比值也高于无机管理茶园。（3）有机管理茶园土壤中的总磷脂脂肪酸含量（PLFAs）增加了29.70%（P<0.05）,且细菌、G^-和放线菌的磷脂脂肪酸的含量显著高于无机茶园（P<0.05）。（4）RDA分析表明,茶园土壤中的微生物群落结构主要受到土壤总氮（TN）、总钾（TK）、烷基C、O-烷基C和羧基C含量的影响（P<0.05）。（5）相关性分析结果显示,有机碳组分中烷基C与总微生物量、真菌、放线菌和菌根真菌含量均呈显著正相关关系。O-烷基C与微生物中真菌、细菌和真菌/细菌的比值也呈显著正相关关系。以上结果表明,对茶园有机管理能调节微生物群落结构,提高土壤有机碳的脂肪化程度,进而影响土壤有机碳的积累和周转机制。     

中国“槟榔黄化病”研究40年——病原、防控措施新进展

自1981年海南省屯昌县首次发现槟榔黄化病（yellow leaf disease of areca palm, YLD）以来,槟榔黄化问题日趋严重,现已成为制约中国槟榔产业可持续发展的最重要的因素。同时,鉴于生产中除槟榔黄化病外,炭疽病、细菌性叶斑病、椰心叶甲、干旱等一些其他因素也可引起槟榔黄化,以及“槟榔黄化病”病原或病因认识上存在混淆的问题,学界暂用“槟榔黄化现象”的表述。近年来,针对上述问题开展了一系列深入研究并取得突破性进展。本文首先简要回顾了中国槟榔黄化病的发生及病原方面的研究进展,介绍了另一种致黄关键新病害——由槟榔隐症病毒1（Areca palm velarivirus 1, APV1）引起的槟榔黄叶病毒病（areca palm leaf yellowing virus disease, ALYVD）,以及其他2种新发现的病毒病害——槟榔坏死环斑病毒病和槟榔坏死环斑病毒病的研究进展。对6个示范基地的病原检测结果表明,部分黄化植株被槟榔黄化植原体（areca palm yellow leaf phytoplasma, AYLP）或APV1单独感染,部分植株被AYLP和APV1复合感染。本文还探讨了槟榔黄化病研究中存在的病原分布不均、含量低引起的检测困难和田间诊断易混淆等问题,并对YLD、ALYVD、叶斑类病害、根腐病害、芽腐病、椰心叶甲、干旱、寒害、除草剂药害等9类因子引起的黄化症状特征进行了总结。进而分析了YLD和ALYVD 防控中存在的问题以及现阶段面临的紧迫形势,从防控策略和具体措施解读了《槟榔“黄化病“防控明白纸》,并指出了其有待进一步完善之处及防控中亟待解决的问题。最后,展望了YLD和ALYVD 2种致黄关键病害综合防控中亟待实施的措施。本文旨在让广大科研工作者和农技人员更好地了解槟榔“黄化病”方面的最新成果。