Effect of root depth penetration on soil nitrogen competitive interactions and dry matter production in pea–barley intercrops given different soil nitrogen supplies

Competition for soil resources plays a key role in the outcome of intercropping systems. In cereal–legume intercrops, competition for soil nitrogen during the vegetative phase greatly influences the final performance of the intercropped species. However, there is a lack of knowledge on the main factors involved in interspecific soil N competitive interactions between species. The dominance of cereals over legumes is often attributed to their faster growing rooting system. Nevertheless, using only field experimental approaches makes it difficult to isolate the effect of one factor because of the strong interactions between processes and the environment. Given the complexity of intercropping systems, dynamic simulation models can be especially helpful for testing hypotheses about the key factors driving competition between species. The present work was designed to investigate, under non-limiting water conditions, through an experimental and modelling approach, whether differences in root depth penetration among pea and barley grown together determined competition for soil N and dry matter accumulation (DM) by each species during the vegetative phase. This hypothesis was tested through several simulated scenarios generated using the STICS crop model. The model was first used to compare competition for soil N according to differences in root depth penetration rates between species. This rooting depth penetration effect was then studied at three levels of soil N supply leading to different degrees of N demand and N stress. A field experiment carried out in 2003 including pea–barley intercrops grown either with 130 kg N ha⁻¹ or without any fertilizer was used to test the model. Experimental results of aboveground biomass, nitrogen accumulation, N₂ fixation and rooting depth monitored regularly during the crop cycle were compared to simulated results. The simulated responses of the intercrops were in agreement with the observations from the experimental dataset. Using the model, it is clear that faster root growth in barley gives it access to more soil nitrogen than pea during the vegetative phase. However, this advantage, which is limited to the vegetative phase, only affects the outcome of the intercrop when soil N supply is low. With higher soil N supplies, soil N sharing is not affected by the differences in rooting depth penetration between species. It appears that with higher N supplies, the differences in N demand between species have more influence on species dominance than differences in rooting depth.     

Effect of irrigation method and N-fertilizer management on rice yield, water productivity and nutrient-use efficiencies in typical lowland rice conditions in China

Alternate wetting and drying irrigation (AWD) has been reported to save water compared with continuous flooding (CF) in rice cultivation. However, the reported effects on yield varied greatly and detailed agro-hydrological characterization is often lacking so that generalizations are difficult to make. Furthermore, it is not known how AWD modifies nutrient use efficiencies and if it requires different N-fertilizer management compared with CF. This study quantified the agro-hydrological conditions of the commonly practiced AWD and compared the impact of AWD and CF irrigations at different N-fertilizer management regimes on rice growth and yield, water productivity, and fertilizer-use efficiencies in five crop seasons in 1999 and 2000 at two typical lowland rice sites in China (Jinhua, Zheijang Province and Tuanlin, Hubei Province), with shallow groundwater tables.Grain yields varied from 3.2 to 4.5 t ha^–1 with 0 kg N ha^–1 to 5.3–8.9 t ha^–1 with farmers N-rates (150 kg N ha^–1 in Jinhua and 180 in Tuanlin). In both sites, no significant water by nitrogen interaction on grain yields, biomass, water productivity, nutrient uptakes and N-use efficiency were observed. Yield and biomass did not significantly differ (P >0.05) between AWD and CF and among N timings. The productivity of irrigation water in AWD was about 5–35% higher than in CF, but differences were significant (P <0.05) only when the rainfall was low and evaporation was high. Increasing the number of splits to 4–6 times increase the total N uptake, but not total P-uptake, and total K-uptake compared with farmers practices of two splits. Apparent Nitrogen recovery (ANR) increased as the number of splits increased, but there was no significant difference in ANR between AWD and CF. During the drying cycles of AWD irrigation, the perched water table depths seldom went deeper than – 20 cm and the soil in the root zone remained moist most of the time. The results suggest that in typical irrigated lowlands in China, AWD can reduce water input without affecting rice yields and does not require N-fertilizer management differently from continuous flooding. The results can be applied to many other irrigated lowland rice areas in Asia which have a shallow groundwater table.     

Rapid multiplication of potatoes in the warm tropics: rooting and establishment of cuttings

Summary To expand potato production in developing countries using cuttings as a source of good quality planting material, requires simple low cost methods to root and establish them. Experiments at a warm tropical site in the Philippines, to determine appropriate methods, showed that simple media ranging from fine sand to clay subsoil mixed with rice hulls enabled rooting which was not improved by hormones. Nitrogen rich media, such as volcanic soil or compost with additional P, were best for developing cuttings into strong transplants but there were no major differences in root and shoot development from cuttings differing in size and age. Tuberizations was favored by increasing the number of nodes buried in the media. Low solar radiation of 7 MJ/m²/day enabled high cutting survival up to root initiation, after which higher radiation supported larger root and shoot production.     

生态足迹深度和广度:构建三维模型的新指标

追踪自然资本存量消耗与流量占用是当前可持续发展研究的核心议题.系统阐述了国际上新近提出的生态足迹三维模型的概念与计算方法,重点对足迹深度和足迹广度两个指标进行了探讨,总结了模型的主要优势,并通过引入资本流量占用率和存量流量利用比两个新指标对模型作进一步完善,在此基础上实证分析了1961-2006年的中国生态足迹.结果表明,中国自 1978年步人生态赤字时代以来,足迹深度增长了近2倍,足迹广度减少了11.84％,因自然资本流量不足导致资本存量大幅肖耗已成为社会发展常态.到2006年时,中国需要2.9倍的国土才能持续支撑其资源消费量.研究表明,三维模型分别从时空两方面表征了人类对资本存量的消耗(足迹深度)和对流量的占用(足迹广度),增强了生态足迹在不同区域、不同时期之间的可比性,并在一定程度上克服了经典模型的评估缺陷.最后指出了三维模型今后发展的主要方向.     

花后干湿交替灌溉对水稻强、弱势粒蛋白质表达的影响

【目的】进一步揭示干湿交替灌溉对水稻籽粒灌浆影响的机制。【方法】两优培九（两系杂交籼稻）和扬粳4038（粳稻）种植于土培池,自抽穗至成熟设置常规灌溉（conventional irrigation,CI）、轻干-湿交替灌溉（alternate wetting and moderate drying irrigation,WMD）和重干-湿交替灌溉（alternate wetting and severe drying irrigation,WSD）3种土壤水分处理,运用双向电泳技术测定水稻强、弱势粒蛋白质表达量。【结果】与CI相比,WMD和WSD对强势粒的灌浆速率和粒重无显著影响;WMD显著增加了弱势粒的灌浆速率和粒重,WSD则显著降低了弱势粒的灌浆速率和粒重。WMD和WSD对强势粒蛋白质表达无显著影响,但WMD上调了弱势粒中丙酮酸磷酸双激酶、甘油醛-3-磷酸脱氢酶、5-甲基四氢叶酸-同型高半胱氨酸甲基转移酶、S-腺苷甲硫氨酸合酶、乙二醛酶I和锰超氧化物歧化酶等蛋白质的表达,WSD则下调了弱势粒中上述蛋白质的表达。WSD还上调了抑制信号传导和能量代谢等有关蛋白的表达。两品种结果趋势一致。【结论】说明在WMD或WSD条件下,弱势粒中多种与灌浆相关蛋白质表达的差异是其灌浆速率和粒重增加或降低的重要原因。     

苹果中间砧入土深度对根系生长及其激素含量和果实产量品质的影响

 以陕西杨凌试验区大田栽培的3 年生‘长富2 号’苹果为材料,结合凤翔、永寿和蒲城等 试验区的调查,研究比较矮化中间砧（M26）入土深度对富士苹果树基砧根系生长分布、根系激素含量和 果实产量品质的影响。结果表明,矮化中间砧入土深度为15 cm 时,树体细根（＜ 2 mm）主要分布在0 ~ 40 cm 土层,细根数比其他处理多13.6% ~ 41.5%,总根数多18.2% ~ 33.3%,根系干质量多11.2% ~ 68.4%, 果实产量高,单果质量大,可溶性固形物含量高,硬度大,可滴定酸含量少,着色率高,品质较好。矮 化中间砧入土深度为15 cm,树体根系中促进生长的IAA、ZR、GA 含量较高,抑制生长的ABA 含量较 少,（IAA + GA + ZR）/ABA 比值较大,有利于刺激根系的生长。研究表明矮化中间砧入土深度为15 cm 时,根系生长旺盛,细根数量较多,能够为果树生长发育提供较多养分,果实品质较好。     

An adaptive approach to intensive green roofs in the Mediterranean climatic region

The present study aims to introduce an adaptive approach to intensive green roofs by evaluating suitable, lightweight substrates and by determining the effect of their depth on the growth and physiological status of Pittosporum tobira L. and Olea europaea L. The two-year study was conducted in outdoor containers (1.2 m × 1.2 m) while treatments included the use of two depths (30 cm and 40 cm) and three different substrates: (a) pumice (Pum) mixed with peat (P) and zeolite (Z) in a volumetric proportion of 65:30:5 (Pum₆₅:P₃₀:Z₅), (b) pumice mixed with compost (C) and zeolite in a volumetric proportion of 65:30:5 (Pum₆₅:C₃₀:Z₅) and (c) sandy loam soil (S) mixed with perlite (Per) and zeolite in a volumetric proportion of 30:65:5 (S₃₀:Per₆₅:Z₅). Each experimental plot was planted with four plants of P. tobira and one plant of O. europaea var. Koroneiki. Measurements included determination of the physical and chemical characteristics of the substrates while plant growth and physiological status were determined through plant growth index, trunk perimeter for olive trees, SPAD measurements and chlorophyll_a+b content. Both the plant species exhibited better growth and higher chlorophyll content in the compost-amended substrate (Pum₆₅:C₃₀:Z₅) due to its higher nutrient content. The 40 cm depth substrate provided minimal improvement in the growth of both the plants at the end of the first year while in the second year the deeper substrate positively influenced the growth of olive trees.     

Water sorption in coated Scots pine (Pinus sylvestris L.) logs and influence of incipient decay

Abstract

Scots pine log specimens were given three different surface treatments and two different orientations of large cracks, and subjected to cyclic wetting and drying. Individual fitting of a mechanistic growth model was used to study the shape of absorption and accumulation curves and the final drying curve. Two parameters from this model (increase/decrease rate and maximum/minimum weight gain) were used for statistical analysis. The results indicate that wood tar results in less accumulated moisture over time than solvent-borne or water-borne coating or no treatment at all. An incipient attack by a white-rot fungus on parts of the material during storage affected water uptake greatly, often overriding surface treatment.     

Simulation of hydrology following various volumes of irrigation to soil with different depths to the water table

Vertical water fluxes at the water table and in the subsoil need to be quantified because of their significance for the supply of water to crops and the control of soil salinization in areas with shallow groundwater. A soil–water–atmosphere–plant (SWAP) model was calibrated using measured values of soil water content and the water fluxes at the water table. The measurements were taken in a field experiment where the depth to groundwater and the volume of irrigation water applied were controlled. The calibrated SWAP model was then used to simulate the soil water content and fluxes at the water table and in the subsoil under different irrigation and groundwater conditions. The predicted values provided a quantitative insight into specific terms in the water balance equation together with soil water fluxes in the subsoil that cannot be measured directly by field instruments. Crops utilized significant amounts of water from deeper soil layers and directly from groundwater, when the volume of irrigation decreased and the depth to the water table was <3.0 m. Depth to the water table significantly influenced water fluxes occurring in the soil profile over the period when evaporation dominated the hydrological cycle. Shallow groundwater is a very significant water resource for meeting the water requirement of crops. In practice, the frequency and quantity of irrigation need to be varied according to groundwater conditions.