黄土区五种土壤抗冲性试验分析

通过室内放水冲刷实验,分析了黄土高坡5种土壤在不同坡度下的下切冲刷过程及影响冲刷的坡度、水流特征以及水流含沙量等影响因素。结果表明,在流量为120 L/h条件下,5种土壤的抗冲系数均随着坡度的增大而降低,且呈现指数回归关系,决定系数R~2较高,土壤抗冲性大小依次为杨凌黏壤土延安砂质黏壤土周至黏壤土志丹砂质壤土靖边砂质壤土;5种土壤的抗冲系数和水流流速均呈现出负相关的线性变化规律;5种土壤的冲刷强度基本都随着坡度的增加而增加,随着冲刷时间的推移,冲刷强度逐渐减小,且坡度越大,前期的冲刷强度越大;5种土壤的抗冲系数与水流含沙量呈现出负相关的线性变化规律,决定系数R~2在0.857 7~0.957 5之间,随水流含沙量的变化,抗冲性越好的土壤其本身的抗冲系数变化越显著。     

不同溶氧量对油麦菜生长、光合指标和产量的影响

通过大棚立体种植油麦菜试验,以灌溉水中溶氧量为试验因素,研究不同溶氧量(T1处理6.8 mg/L、T2处理8 mg/L、T3处理7.4 mg/L、T4处理1.2 mg/L)对油麦菜生长量、光合指标、植株鲜质量、干质量和产量的影响。结果表明,(1)不同溶氧量对油麦菜株高、叶片数和茎粗有显著性影响;各处理株高均值次序为:T2处理T3处理T1处理T4处理,叶片数均值次序与株高的相同;(2)不同溶氧量对叶绿素质量分数、净光合速率、蒸腾速率、气孔开度有显著性影响,但是对胞间CO2摩尔分数影响并不显著;(3)不同溶氧量对单株鲜质量和干质量影响显著,T2处理的单株鲜质量和干质量最大,分别为56.25、10.71 g;T4处理的最小,分别为42.64、3.52 g;T1、T2、T3处理与T4处理相比产量分别提高了13.2%、22.6%、28.3%。以产量为研究目标时,7.4 mg/L溶氧量+灌水定额45 m3/hm2为最佳组合。     

山羊终末呼吸和血液安氟醚浓度变化及其与血气,血压的关系

６头山羊在吸入安氟醚５，１５，３０，４５，６０，７５和９０ｍｉｎ时，同步测定终末呼气和血液中安氟醚浓度，血气及血压等。结果显示：在开档期间，随吸入时间的延长，终末呼气和血液安氟醚浓度均上升，但停止供药，两浓度则下降；随吸入安氟醚浓度的增加，血气和血压发生明显的变化，ｐＨａ减少，ＰａＣＯ２升高，血压下降，平均动脉压与终末呼气安氟醚浓度高度相关（ｒ＝－０．９７２１）。随安氟醚浓度的减少，血气和血压也     

晚秋叶施高浓度肥料对梨树矿质营养状况的影响

在梨树上进行尿素，磷酸二氢钾，硼肥及其混合液的高浓度晚秋叶面喷施，对处理后休眠期枝条及翌年花序，叶片中相应矿质成分含量进行分析，结果表明晚秋叶施高浓度肥料均能显著增加梨树休眠期枝条中相应矿质成分的含量，并促进其在枝条中的贮藏运输。     

基于等厚干涉原理测量NaCl溶液浓度

溶液浓度是一个重要物理量。溶液浓度的变化会引起折射率变化。根据等厚干涉的原理,提出通过测量溶液的折射率来确定其浓度的光学方法。以NaCl溶液为例,测量误差低于3％。     

不同光照条件下钙浓度对水养漳州水仙花品质的影响

通过不同光照条件下不同钙浓度对水养漳州水仙花品质影响的研究发现:光照能极显著影响水仙花的品质,钙浓度对水仙花的品质无显著影响。但光照与钙共同作用能极显著影响水仙花的品质,并且以自然光照下0.2~0.6g/L的钙浓度为最佳。     

半开放式CO_2和温度递增系统(CTGC)的改进:CO_2浓度控制效果

环境控制模拟系统,是开展农田生态系统对全球气候变化响应研究的有效手段,但目前应用于试验中的模拟系统均存在一定局限,如CO_2气体过量消耗、试验成本较高、模拟的试验环境与真实的自然环境差异较大、试验空间有限、不易重复等。针对这些问题,本研究对半开放式CO_2浓度和温度递增模拟系统(CTGC)进行了硬件升级和设计改进,针对其CO_2浓度的控制效果包括CO_2浓度监测、CO_2气体释放两大系统进行改进,使其能达到精准控制CO_2气体释放,降低试验成本,精确模拟未来高CO_2浓度的生产环境,其空间面积较大,适合多种作物同时试验。改进后的系统利用电磁阀组和CO_2浓度检测传感器组成的多通道监测系统,实时检测各处理区域内的CO_2浓度,实现精准监测。在CO_2气体释放源端,采用比例调节式减压器,有效减少了CO_2从储气罐中被减压后在气体管路中的压力积蓄,控制CO_2气体精量释放;系统将CO_2释放方式由纵向改为横向,释放管道由主管加支管组成,由控制流量调节阀将主管与支管相连接,使气室内形成均匀的CO_2释放区域,从而达到CO_2浓度梯度升高的模拟效果。试运行结果表明,改进后的CTGC系统可以实现CO_2浓度387±4.5、441±13.4、490±20.9、534±24.3和567±28.9μmol·mol-1的梯度递增,系统对环境变化的响应速度加快,能够精确实时监测气室内各处理区域CO_2浓度的变化,并实现CO_2气体的精量释放;系统内的CO_2浓度梯度递增趋于稳定,从而更好地模拟大气CO_2浓度逐渐升高的过程,满足作物对气候变化响应研究的需要。     

Effect of time of application and amount of nitrogen fertilizer on seed yield and concentration of oil in canola (Brassica napus)

The seed (grain) yield increases (responses) and concentration of oil in seed responses of canola (Brassica napus L.) to applications of fertilizer nitrogen (N), as urea (46% N), was measured in eight field experiments in south-western Australia (SWA). Nitrogen was applied at five different times of application, either at sowing or at three to four weekly intervals until 12–16 weeks (0, 3, 6, 9, 12 or 0, 4, 8, 12, 16) after seedling emergence. Canola, sown in late May to early June, was grown on a range of soil types in different locations of SWA. The greater the amount of N applied and the closer N was applied to the sowing of the canola seed usually gave the largest seed yield increase at both higher rainfall sites (> 500 mm) and lower rainfall sites (<350 mm). Maximum seed yield of canola were reached within nine weeks after seedling emergence. The exception was for a sandy soil (Fluventic Lithic Xerochrept; Brown Tenosol) at Narrogin where applications of N at six, nine, or 12 weeks after emergence gave higher yields compared to N applied earlier mainly due to N leaching in June and July.

The amount of N required for 90% of maximum seed (N_90%Y) yield ranged from five to 58 kg N ha^?1 with the amount depended on location and growing season. For six of the eight sites the higher amounts of N for N_90%Y were required at sowing and three weeks after emergence. Similarly, N use efficiency (NUE, kg grain produced kg N applied^?1) tended was highest for either the N applied at sowing or within three to four weeks after emergence of seedlings. The exception was for a sandy soil at Narrogin where applications of N at six, nine, or 12 weeks after emergence gave higher NUE compared to N applied earlier. N use efficiency decreased as the amount of N increased for all times of N application. Generally, the amount of N applied decreased the oil concentration of canola seed at each time of application. However, the effect of the time of application of N fertilizer on the decrease in oil concentration of canola seed was largest with the highest N level applied at 12 or 16 weeks after seedling emergence. The percentage the oil concentrations decreased as the amount of N applied increased varied with location and growing season. Further research work is required to elucidate the interaction between the growing season, possible rainfall and temperature, and the effects of N on grain yield and oil concentration in seed.     

Growth and nutrient and nitrate accumulation of lettuce under different regimes of nitrogen fertilization

Abstract

For plant growth and composition, the effects of fertilizers including blood meal (BLO), cottonseed meal (CSM), dehydrated cow manure (COW), and urea (UREA) factored with lettuce (Lactuca sativa L.) of different morphological phenotypes including iceberg, romaine, loose head, and loose leaf were studied in a greenhouse. Lettuce growth increased with increasing nitrogen (N) applications from 0 to 800?mg N/pot (kg), but the top application of BLO, CSM, or UREA suppressed yields. Lettuce grown with BLO, CSM, or UREA had higher concentrations of N than with COW. Nitrate-N concentration in leaves of all varieties exceeded some standards at high application of organic fertilizer or urea except for COW. In general, increasing N application resulted in higher concentration of NH₄-N in lettuce with increases in applications of fertilizers. Organic fertilizers and urea were equally effective in supporting growth and affecting nutrient accumulation in lettuce if sufficient N was supplied.     

Critical nitrogen content and nitrogen nutrition index for sweetpotato crop

Abstract

Sweetpotato is an important tuber crop for the food security in Island countries of the South Pacific. The allometric relationship between tissue nitrogen (N) concentration and aerial dry matter is unknown. We determined critical N (N_c) content from vegetative stage to harvesting, and estimated the range of variation in N nutrition index (NNI) from two field experiments with varied rates of N (0, 25, 60, 125 and 180?kg N ha^?1 in 2015 and 0, 50, 125, 175 and 250?kg N ha^?1 in 2017). A unified critical N curve (N_c = 3.338?W^?0.307) where W?=?aerial dry matter with W?≥?1.38 t ha^?1, was constructed based on the N concentration in the aerial dry matter. The calculated NNI ranged from 0.69 to 1.23 in 2015 and 0.54 to 1.17 in 2017. The preliminary N_c dilution curve and NNI determined could potentially be used as a parameter for N management.