氮肥品种和用量对水稻产量和镉吸收的影响研究

采用盆栽试验,研究了Cd污染土壤上,不同氮肥品种和用量对水稻产量和Cd吸收的影响。结果表明,与磷钾配施的4个氮肥处理中,施用尿素处理水稻产量最高,其次为施(NH4)2SO4和NH4Cl处理,施NH4NO3处理水稻产量最低。与施(NH4)2SO4、NH4NO3和尿素处理相比,施NH4Cl处理可显著增加水稻对Cd的吸收,并促进Cd由秸秆向籽粒的转移;而其他3种氮肥对水稻秸秆和籽粒中Cd含量的影响效应相当。适量尿素[0.2g(N)·kg-1]处理能显著降低水稻籽粒Cd含量,而不施尿素和高量尿素处理都显著提高了水稻籽粒中的Cd含量。研究表明,在Cd污染的水稻土上,采用抗Cd污染的水稻品种和优化肥、水管理措施,可使稻米中Cd含量低于国家无公害大米的限量指标。     

土壤养分类型与小麦最佳施肥比例及最大施肥量的关系

在同一试验中采用以氮定磷和氮磷等比条件下同步增加氮磷用量的方法,对土壤养分类型与小麦最佳施肥比例和最大施肥量进行了田间试验。试验表明,不同养分类型的土壤种植小麦,均存在平衡与不平衡土壤养分类型和特定的最佳施肥比例,而小麦最大氮磷施用量严重受试验设计方法的影响。田间试验以最佳氮磷施肥比例条件下同步增加用量设计方法确定的最大氮磷用量较为准确,而以氮定磷的试验方法只有其中有一个处理的施肥比例和用量接近小麦最大氮磷用量的情况下,试验结果才接近实际情况。     

华北平原典型冬小麦农田生态系统能量平衡与闭合研究

准确量化分析地气之间的物质和能量交换对于水资源管理和农业可持续发展是十分重要的。能量平衡闭合是评估观测数据准确性和分析地表能量平衡的一个重要的评价指数。本研究利用开路涡度相关系统和全要素自动气象站对华北平原典型冬小麦农田生态系统2013—2014年度的能量通量及常规气象要素进行了连续观测,分析了冬小麦农田各能量通量的日变化和年变化特征,计算冬小麦在4个生育时期(出苗期、越冬期、拔节期和灌浆期)的能量闭合和波文比。结果表明:在日尺度上,选取的4个生育时期净辐射和各能量分量的日变化趋势均为单峰二次曲线,净辐射、显热通量和潜热通量的峰值出现在12:00—13:00,土壤热通量的峰值出现在14:00—15:00。在年尺度上,净辐射和潜热通量的变化趋势较为一致,均在越冬期达到最低值114.51 W·m~(-2)和13.47 W·m~(-2),而在灌浆期达到最大值327.02 W·m~(-2)和116.56 W·m~(-2)。选取的4个生育时期的代表性观测日期能量闭合良好,能量闭合率分别为0.49、0.77、0.81和0.76。4个生育时期内波文比值日变化趋势均呈倒"U"型,出苗期波文比在14:00达到最大值2.12;越冬期、拔节期和灌浆期在10:00左右达到最大值,分别为1.48、0.31和0.58。本文的定量化结果可为华北平原农田生态系统水热通量等研究提供依据。     

Specific Responses of Soil Microbial Residue Carbon to Long-Term Mineral Fertilizer Applications to Reddish Paddy Soils

Mineral nutrient inputs to soil may alter microbial activity and consequently influence the accumulation of microbial residues. In this study, we investigated the effects of application rates and ratios of mineral fertilizers on the microbial residue carbon(MRC) of reddish paddy soils after long-term(15-year) fertilizer applications in southern China. Contents of three soil amino sugars as microbial residue contents were determined and MRC were calculated based on amino sugars. Results showed that three individual amino sugar contents increased as fertilizer application rates increased until maximum values were reached at a rate of 450-59-187 kg ha~(-1) year~(-1)(N-P-K). The three amino sugar contents then declined significantly under the highest mineral fertilizer application rate of 675-88-280 kg ha~(-1) year~(-1)(N-P-K). In addition, to enhance the microbial residue contents, it was more beneficial to double P(N:P:K= 1:0.26:0.41) in fertilizers applied to the P-deficient reddish paddy soils than to double either N(N:P:K = 2:0.13:0.41) or K(N:P:K= 1:0.13:0.82). The contents of the three individual amino sugars and microbial residues under different fertilizer application rates and ratios were significantly and positively correlated with soil organic carbon(SOC), total N, total P, and p H. Increases in values of the fungal C to bacterial C ratios showed that soil organic matter(SOM) stability increased because of the fertilizer applications over the past 15 years. The contents and ratios of amino sugars can be used as indicators to evaluate the impact of mineral fertilizer applications on SOM dynamics in subtropical paddy soils. The results indicated that fertilizer applications at a rate of 450-59-187 kg ha~(-1) year~(-1)(N-P-K) may improve crop yields, SOC contents, and SOC stability in subtropical paddy soils.     

淤地坝赋存信息在流域侵蚀产沙研究中的应用

黄土高原淤地坝在拦蓄大量泥沙的同时,也赋存了大量环境变化信息。该文从淤地坝赋存信息在小流域侵蚀产沙速率、泥沙来源和泥沙输移比研究方面的作用进行了归纳和总结,分析了目前研究中存在的问题,提出了今后研究的发展方向,以期能为更好地利用这些赋存信息,发挥其在黄土高原土壤侵蚀和环境演变过程研究中的作用提供参考。     

多参数输入对ABS模糊控制器的影响研究

以地面附着系数最大为目标,利用模糊控制的方法,以dφ/ds和(dφ/ds)/dt为模糊控制器的输入,制动压力增量ΔP为输出,设计了一种新的ABS控制系统。在MATLAB/simu link环境中进行了仿真,并进行了试验,结果表明,新设计的ABS控制系统改善了制动时制动油压波动过大的现象,从而缩短了制动距离,提高了制动性能。     

稻谷热风辅助射频干燥工艺及相关品质研究

新型热风辅助射频(HA-RF)技术已被证实在稻谷杀虫方面具有良好的效果,为探究其同步杀虫干燥的应用潜力,本研究重在探究HA-RF在稻谷干燥方面的效能,开发稻谷HA-RF干燥工艺并研究相关的品质变化.结果表明:极板间距为10.0 cm(射频加热速率6.10℃/min),干燥温度为60℃,样品厚度为3.0 cm时,稻谷HA-RF干燥效能最佳;HA-RF与热风(HA)干燥相比可缩短干燥时间34.6％,单位能耗也更低.此外,HA-RF与HA干燥相比对稻谷精米率、整精米率和爆腰率的影响无显著差异,但HA-RF干燥可以更好地保留维生素E,且对样品颜色和微观结构的影响也较小.该研究表明HA-RF是一种比HA干燥更加高效节能的技术,且干燥后稻谷品质更好,在稻谷同步干燥杀虫上具有一定应用潜力.     

优质茶鲜对品质成份在年周期中的动态变化

通过全年茶季各阶段测定,分析了芽叶的机械组成,叶、梗及整体的水浸出物、茶多酚、氨基酸、儿茶素总量和纤维素的动态变化。探明叶/梗比值可以作为鲜叶嫩度指标;而5个品质成份中,以水浸出物和氨基酸的季节性差异达极显著水平,并据此建立回归方程。     

Variability in energy partitioning and resistance parameters for a vineyard in northwest China

Grapevines are extensively grown in the semiarid and arid regions, but little information is available on the variability of energy partitioning and resistance parameters for the vineyard. To address this question, an eddy covariance system was applied to measure energy balance over a vineyard in northwest China during 2005-2006. Result indicated that 2-year average Bowen ratio (β) of vineyard was 1.0, canopy resistance (r_c) 289.3 s m⁻¹, aerodynamic resistance (r_a) 9.7 s m⁻¹ and climatological resistance (r_i) 117 s m⁻¹. This implied that the annual energy was split almost equally between sensible heat and latent heat. Compared to the corresponding values in other ecosystems reported by Wilson et al. [Wilson, K.B., Baldocchi, D.D., Aubinet, M., Berbigier, P., Bernhofer, C., Dolman, H., Falge, E., Field, C., Goldstein, A., Granier, A., Grelle, A., Halldor, T., Hollinger, D., Katul, G., Law, B.E., Lindroth, A., Meyers, T., Moncrieff, J., Monson, R., Oechel, W., Tenhunen, J., Valentini, R., Verma, S., Vesala, T., Wofsy, S., 2002. Energy partitioning between latent and sensible heat flux during the warm season at FLUXNET sites. Water Resource Research 38, 1294-1305.], the vineyard had a higher β, r_c and r_i than deciduous forests, corn and soybean, and grassland. Such difference was mainly attributed to (1) serious water stress in 2005, which resulted in a greater r_c up to 364.4 s m⁻¹; (2) sparse canopy with row spacing of 2.9 m and plant spacing of 1.8 m; (3) warm-dry climate and high attitude (1581 m) along with higher r_i and lower psychrometer (54 Pa K⁻¹) in the arid region of northwest China. These characters of vineyard revealed varying process of energy partitioning and surface resistance, and provided a scientific basis in understanding and modeling water and energy balance for the vineyard in the semiarid and arid regions.     

Water production functions of wheat (Triticum aestivum L.) irrigated with saline and alkali waters using double-line source sprinkler system

Expected yield losses as a function of quality and quantity of water applied for irrigation are required to formulate guidelines for the effective utilisation of marginal quality waters. In an experiment conducted during 2004-2006, double-line source sprinklers were used to determine the separate and interactive effects of saline and alkali irrigation waters on wheat (Triticum aestivum L.). The study included three water qualities: groundwater (GW; electrical conductivity of water, ECw 3.5 dS m⁻¹; sodium adsorption ratio, SAR 9.8 mmol L⁻¹; residual sodium carbonate, RSC, nil) available at the site, and two synthesized waters, saline (SW; ECw 9.4 dS m⁻¹, SAR 10.3 mmol L⁻¹; RSC nil) and alkali (AW; ECw 3.7 dS m⁻¹, SAR 15.1 mmol L⁻¹; RSC 9.6 meq. L⁻¹). The depths of applied SW, AW, and GW per irrigation ranged from 0.7 to 3.5 cm; the depths of applied mixtures of GW with either SW (MSW) or AW (MAW) ranged from 3.2 to 5 cm. Thereby, the water applied for post-plant irrigations using either of GW, SW or AW ranged between 15.2 and 34.6 cm and 17.1 and 48.1 cm during 2004-2005 and 2005-2006, respectively and the range was 32.1-37.0 and 53.1-60.0 cm for MSW or MAW. Grain yields, when averaged for two years, ranged between 3.08 and 4.36 Mg ha⁻¹, 2.57 and 3.70 Mg ha⁻¹ and 2.73 and 3.74 Mg ha⁻¹ with various quantities of water applied using GW, SW and AW, respectively, and between 3.47 and 3.75 Mg ha⁻¹ and 3.63 and 3.77 Mg ha⁻¹ for MSW and MAW, respectively. The water production functions developed for the two sets of water quality treatments could be represented as: RY = 0.528 + 0.843(WA/OPE) − 0.359(WA/OPE)² − 0.027ECw + 0.44 × 10⁻²(WA/OPE) × ECw for SW (R² = 0.63); RY = 0.446 + 0.816(OPE/WA) − 0.326(WA/OPE)² − 0.0124RSC − 0.55 × 10⁻⁴(WA/OPE) × RSC for AW (R² = 0.56). Here, RY, WA and OPE are the relative yields in reference to the maximum yield obtained with GW, water applied for pre- and post-plant irrigations (cm), and open pan evaporation, respectively. Crop yield increased with increasing amount of applied water for all of the irrigation waters but the maximum yields as obtained with GW, could not be attained even with increased quantities of SW and AW. Increased frequency of irrigation with sprinklers reduced the rate of yield decline with increasing salinity in irrigation water. The sodium contents of plants increased with salinity/alkalinity of sprinkled waters as also with their quantities. Simultaneous decrease in potassium contents resulted in remarkable increase in Na:K ratio.