Validation of a root water uptake model to estimate transpiration constraints

Experimental results obtained from a greenhouse trial with common bean (Phaseolus vulgaris L.) plants performed to test model hypotheses regarding the onset of limiting hydraulic conditions and the shape of the transpiration reduction curve in the falling rate phase are presented. According to these hypotheses based on simulations with an upscaled single-root model, the matric flux potential at the onset of limiting hydraulic conditions is as a function of root length density and potential transpiration rate, while the relative transpiration in the falling rate phase equals the relative matric flux potential. Transpiration of bean plants in water stressed pots with four different soils was determined daily by weighing and compared to values obtained from non-stressed pots. This procedure allowed determining the onset of the falling rate phase and corresponding soil hydraulic conditions. At the onset of the falling rate phase, the value of matric flux potential M_l showed to differ in order of magnitude from the model predicted value for three out of four soils. This difference between model and experiment can be explained by the heterogeneity of the root distribution which is not considered by the model. An empirical factor to deal with this heterogeneity should be included in the model to improve predictions. Comparing the predictions of relative transpiration in the falling rate phase using a linear shape with water content, pressure head or matric flux potential, the matric flux potential based reduction function, in agreement with the hypothesis, showed the best performance, while the pressure head based equation resulted in the highest deviations between observed and predicted values of relative transpiration rates.     

不同肥料用量和配比对西瓜产量、品质及养分吸收的影响

为探索西瓜的适宜施肥量和养分配比, 通过田间试验, 研究了不同肥料用量和配比对西瓜产量、品质及养分吸收的影响。结果显示: 与习惯施肥处理相比, 减氮磷钾处理的西瓜产量、Vc含量分别增加0.77%、17.18%, 还原糖含量、硝酸盐含量分别减少12.56%、27.94%; N、P₂O₅、K₂O养分总量相同、比例不同的3个处理间相比, 减氮磷增钾处理的西瓜产量、Vc含量、还原糖含量均最高, 硝酸盐含量最低; 习惯施肥、减氮 磷钾、减氮磷、减氮磷增钾4个处理的西瓜秧中N、P₂O₅、K_{2O含量比例分别为: 1︰0.18︰2.26、1︰0.22︰2.66、1︰0.26︰2.75、1︰0.19︰2.46; 西瓜皮中N、P2O5、K2O含量比例分别为: 1︰0.34︰2.78、1︰0.34︰2.60、 1︰0.30︰2.37、1︰0.29︰2.14。综合考虑各项指标, 在本试验条件下, 施肥总量比习惯施肥量减少36%、N︰P2O5︰K2O为1︰0.41︰1.28是西瓜最优施肥处理。}     

Influences of ultra‐violet (UV)‐blue light radiation on the growth of cotton. II. Photosynthesis,leaf anatomy,and iron reduction

Cotton (Gossypium hirsutum L.) plants grown under low pressure sodium lamps (LPS) developed chlorosis which was similar in appearance to iron‐stress induced chlorosis, while plants under cool white fluorescent lamps (CWF) at the same level of photosynthetically active radiation (PAR) developed normally. These illumination sources differ in spectral irradiance; CWF lamps emit ultra violet (UV), whereas LPS lamps do not. Ultraviolet radiation is capable of reducing Fe³⁺ to Fe²⁺ through a chlorotic leaf which may be important in establishing an active iron fraction in the leaf. Root reduction of Fe³⁺ to Fe²⁺ was lacking in Fe‐stressed cotton under LPS light, but was present under CWF light. Net photosynthesis, photosynthetic electron transport, and leaf chlorophyll content were lower under LPS than CWF light in most of the growing media studies (soil or solutions with nitrate‐ or ammonium‐nitrogen supplied). Chloroplast ultrastructure and leaf thickness were also altered by LPS irradiance. Electron microscopic studies with plants grown in nutrient solutions for 4 weeks suggested that chioroplastic granal disorganization was more directly associated with diminished iron supplies than with light source. However, plants grown in soil for 6 weeks under LPS light had granal disorganization similar to that found in iron‐stressed plants. These studies suggest an important role for UV radiation in influencing the activity of iron in plants.     

有机肥部分替代氮肥的盐碱土壤改良与水稻增产效应研究

本研究旨在揭示利用有机肥部分替代氮肥实现作物增产和土壤改良的可能性及其机理。以南粳9108为供试水稻品种,设置4个处理:常规施肥(T1),低量自配有机肥部分替代氮肥(T2),高量自配有机肥部分替代氮肥(T3),不施肥(CK),T1、T2和T3采用等氮量设计(315 kg/hm²),开展田间试验。研究结果表明:较常规施肥,有机肥部分替代氮肥能够显著降低土壤pH、提升土壤有效磷和速效钾、增强脲酶和碱性磷酸酶活性、增加土壤有机质和碱解氮;能够显著增加收获时的水稻干物质积累量,一定程度地提升水稻株高,促进水稻分蘖并且增加穗粒数、结实率和千粒重。有机肥部分替代氮肥能够实现土壤改良和水稻增产。     

降温对刺参免疫酶、可溶性蛋白及可溶性糖

为初步探讨降温对刺参免疫酶、可溶性蛋白和可溶性糖的影响,采用2种降温模式,对刺参进行室内水温缓降实验和骤降实验。结果表明：（1）2种降温模式下刺参体壁可溶性蛋白有显著的差异(P<0.05);骤降过程中,不同的降温幅度(9.5、5.5、3.5℃)对可溶性糖、可溶性蛋白有显著的影响(P<0.05);缓降过程中,可溶性糖和可溶性蛋白在2℃点上变化较明显。（2）2种降温模式下刺参体腔液中CAT和SOD活性有显著的差异(P<0.05);骤降过程中,不同的降温幅度对CAT、SOD和AKP活性有显著的影响(P<0.05);缓降过程中,几种免疫酶的活性随着温度的降低都产生了较为明显的变化。温度低于2~4℃以及降温幅度为9.5℃都会对刺参的免疫和生理指标产生显著的影响;缓降对刺参免疫指标的影响比骤降要小。     

“气候智能型农业”：理念与实践

[目的]为适应气候变化和保障全球粮食安全,联合国提出了发展“气候智能型农业”的理念与实践途径,目标是实现提高农业生产力、适应气候变化和减少温室气体排放三个方面的共赢。[方法]该文阐述了“气候智能型农业”产生的背景、内涵和相关的技术方法,并介绍了不同国家的实践模式和成功案例。[结果]“气候智能型农业”是全球农业转型发展的新方向,可通过土壤、水分、遗传资源和产业价值链等方面的综合管理引导当前农业系统做出必要改变,以共同解决粮食安全和应对气候变化的问题。[结论]中国亟待从全球经验和本国国情出发,推动“气候智能型农业”的发展。     

Reducing labour and input costs in soybean production by smallholder farmers in south-western Kenya

We conducted experiments in 2006 and 2007 in south-western Kenya to reduce labour and input cost of soybean production through different planting systems (point-placement was compared to planting in trenches and broadcasting), weeding frequencies (once or twice), and the use of local inputs (at 20 kg P ha⁻¹). Di-ammonium phosphate (DAP) was compared to manure, ashes, combinations of those, 1/2 Tithonia 1/2 DAP (TD) and no input. 1/3rd of the labour was saved when placing seeds in trenches as compared to individual holes without losing significant grain yield. Broadcasting requires 1/9th of the planting time while losing only 15% grain. 5% grain was lost by weeding once instead of twice, while saving 36% of the time. The time saved at planting can be more productively invested in collecting inputs. Plots without input yielded 537 kg ha⁻¹ grain and 642 kg ha⁻¹ biomass in 2006. Inputs increased both grain and biomass yields significantly with 27–51%, without significant difference between local and mineral inputs (with exception of TD). Using local input is thus a reasonable decision for farmers. Farmers concluded that the experiments had led to options for different types of farmers, with different access to resources, to increase their soybean production.     

木薯废弃物代替草炭减量在红掌盆栽基质上的研究应用

以红掌为试验材料,研究木薯废弃物加工生产的熟料基质替代草炭减量作为无土盆栽基质的可行性,结果表明:用木薯废弃物加工生产的熟料介质替代草炭,降低草炭含量的基质配方同样可以获得良好的栽培效果。初步筛选出适宜红掌生长开花的木薯废弃物加工生产的熟料基质优化组合体积配比为熟料介质40%+草炭60%。用该熟料介质替代草炭,使得草炭减量的红掌无土盆栽基质是可行的。     

基于信息扩散理论的辽宁省水稻减产率风险评估

利用辽宁省1993—2013年的水稻产量资料,采用直线滑动平均法计算出趋势产量,并基于信息扩散理论的风险分析模型,以平均减产率和风险指数为指标,对辽宁省水稻减产率进行风险评估。根据评估结果,将辽宁省划分为5个区域:低风险区、较低风险区、中等风险区、较高风险区、高风险区。结果表明:盘锦地区气候条件好,土壤肥沃,是水稻生长适宜区;辽西地区由于干旱和热量条件,水稻生产风险较高,不适宜种植水稻。     

影响废铁屑还原土壤中4-硝基苯胺的因素研究

[目的]推动铁屑在治理有机物污染土壤中的实际应用。[方法]利用机械厂废弃铁屑在常温常压下对土壤中的4-硝基苯胺（p—NA）进行还原,并对影响还原反应的各种因素进行研究：[结果]废铁屑可将土壤中的p-NA还原成苯二胺,提高了其生物降解性。在土壤中p-NA的初始浓度为1．3×10^-3mol／g、铁屑加入量67mg／g、加水量0．33ml／g、土壤初始pH值为6．45条件下,经过4h反应后,p—NA的还原率可达100％。铁屑的前处理方式对p-NA还原率影响的大小顺序为：酸洗〉水洗〉碱洗;在一定范围内,增加铁屑用量和土壤含水量能有效提高p—NA的还原率;土壤酸度、有机质含量和反应温度对p-NA还原效率的影响较小.[结论]废铁屑可将土壤中的P-NA还原成苯二胺,提高了其生物可降解性,为铁屑治理有机物污染土壤提供了科学借鉴：