基于SAR与Landsat TM的小区域稻田的识别研究——以南京市江宁区为例

以南京市江宁区为研究区域,根据区域特征、作物物候期和水稻的生长特点,采用分层分类的方法提取稻田分布信息。通过比较多时相SAR数据、TM和多时相SAR融合与TM和单时相SAR融合数据识别水稻的精度和提取的水稻种植面积,分析了不同数据对区域多云雨,不同种植方式、面积小且分布破碎的水稻稻田的识别程度,并根据野外实地走访调查分析了主要影响因素。结果表明:多时相SAR数据、TM和多时相SAR数据的水稻识别精度都高于72%,高于TM和单时相SAR融合数据的结果;前两者提取的水稻种植面积和稻田分布接近,主要影响因素是地物分布、不同种植方式水稻物候期和水稻稻田面积小且分布破碎。     

重庆地区水稻土胶膜及基质的研究

对重庆地区水稻土胶膜及基质土壤中某些元素含量情况及相互之间的关系进行了研究。结果表明:胶膜的pH值、有机质含量均明显高于基质土壤,且有机质含量差异极显著(P<0.01);胶膜中全氮、全磷含量高于其基质土壤且差异均达到极显著水平(P<0.01),全钾在胶膜与基质土壤中含量无明显变化,胶膜中铜、锌含量总体上高于其基质土壤,二者间锌含量差异达到显著水平(P<0.05);供试胶膜中全铁含量极显著高于基质土壤(P<0.01),全锰含量无一致性规律,胶膜中全锰含量总体上较基质土壤高,但二者差异不显著(P>0.05);供试胶膜中全磷与全铁含量显著相关(r=0.606*,n=12),具有较好的伴生关系,胶膜中铜与铁、锰含量均极显著相关(r铜铁=0.792**,r铜锰=0.737**;n=12),但铜与锰伴生关系较好,而锌与铁的伴生关系较好。     

The effect of storage pressure on the mechanical properties of paddy grains

To investigate the effect of storage pressure and storage time on the mechanical properties of paddy grains, an experimental study was carried out to determine the mechanical properties of paddy grains compressed at minor axis orientation using the Texture Analyzer. The paddy grains were stored under different pressures and for different time. The results showed that as the storage pressure increased from 0 to 300 kPa, the rupture force of paddy grains stored for 60 days decreased from 81.58 to 73.78 N, the rupture energy from 8.10 to 6.27 mJ, the rupture strain from 0.1392 to 0.1168, the apparent contact modulus of elasticity from 171.32 to 57.68 MPa and the maximum contact stress from 40.84 to 19.11 MPa. All of the mechanical properties of the paddy grains exhibited a linear relationship with storage pressure. As for the paddy grains stored under the pressures of 77, 100, 139, 200 kPa, as the storage time increased from 0 to 60 days, the rupture force of the paddy grains decreased from 81.58 to 79.58 N, 81.58 to 79.12 N, 81.58 to 78.21 N and 81.58 to 76.96 N; the rupture energy decreased from 8.10 to 7.55 mJ, 8.10 to 7.35 mJ, 8.10 to 7.08 mJ and 8.10 to 6.85 mJ; the rupture strain decreased from 0.1392 to 0.1309, 0.1392 to 0.1283, 0.1392 to 0.1257 and 0.1392 to 0.1213. The apparent contact modulus of elasticity decreased from 171.32 to 135.97 MPa, 171.32 to 121.77 MPa, 171.32 to 110.59 MPa and 171.32 to 83.32 MPa; the maximum contact stress decreased from 41.16 to 35.00 MPa, 41.16 to 32.45 MPa, 41.16 to 30.32 MPa and 41.16 to 14.97 MPa, respectively. The results revealed that both storage pressure and storage time have a significant effect on the mechanical properties of paddy grains.     

Estimating Land Use Impacts on Regional Scale Urban Water Balance and Groundwater Recharge

Anthropogenic activities have exerted increasingly large-scale influences on terrestrial ecological systems from the past century, primarily through agriculture; however, the impact of such changes on the hydrologic cycle is poorly understood. As one of the important land use (LU) in the coastal Dogo Plain of the Seto Inland Sea, Japan, paddy fields have been decreasing with the increase in urbanization in recent decades. As the main source of water in the Dogo Plain, groundwater plays an important role in providing people with fresh water and contributing to stream base flow. The purpose of this study is to analyze the water resource and evaluate the effect of LU change on groundwater table fluctuation in this coastal plain. Firstly, the observations of groundwater table and the investigation of water balance were carried out in this alluvial plain. Then, a distributed four-block three-layer water balance model was employed to analyze the groundwater table fluctuation with response to the change of paddy field area. Moreover, the role of paddy field in recharging groundwater in the basin has been clarified. Results show that groundwater table depends not only on rainfall and discharge from rivers, but also on irrigation water and topology of the study area. The net groundwater recharge was positive in irrigation periods whereas that in non-irrigation periods was nearly equal to zero or negative. The results of this study would be helpful to the urban development policy and land use planning decision.     

双草醚在稻田土壤中的降解及其影响因子的研究

采用了实验室模拟方法研究了双草醚在不同土壤中的降解动态。结果表明,在未灭菌的土壤中,双草醚三种浓度(2.0、10.0、50.0mg kg-1)处理的半衰期为7.6~10.3d,远远小于在灭菌土壤中3种添加浓度处理的半衰期(43.3~61.9 d);双草醚在偏酸土壤中降解较快,随着土壤含水量的增加和环境温度的增高,双草醚降解速度加快。4种试验因子中土壤微生物是影响双草醚降解的主要因素,有利于土壤中微生物生长的环境因素,如偏酸的土壤、较高的温度和土壤湿度等,也能促进土壤中双草醚的降解。     

施用涂层尿素对水田土壤氮去向及其利用率的影响

采用水稻盆栽试验方法,研究施用涂层尿素对水田土壤氮的挥发、土壤残留、水稻吸收三个去向及其氮素利用率的影响。研究结果表明:施用涂层尿素可显著抑制NH3和NOX挥发损失,NH3和NOX挥发量之和的减少幅度为22.1%~24.8%;使土壤中全氮含量增加,增加幅度为1.9%~2.1%。等氮用量条件下,施用涂层尿素可极显著提高氮素利用率,其提高幅度随施用量增大而减小;使水稻经济产量显著增加,中用量和高用量水平处理经济产量增加幅度分别为21.8%和21.5%。说明施用涂层尿素不仅能提高水田土壤氮素利用率,而且可减轻生态环境污染。     

黔中地区水稻土的含硒量及其对糙米硒含量的影响

通过贵州开阳县水稻土硒含量特征和该区水稻硒含量之间关系的调查研究表明:开阳县水稻土水溶性硒含量高于一般水稻土水溶性硒的临界值(0.01μgg-1),这与该区的成土母质、地形等因素有关。富硒水稻土使水稻对硒的吸收增加,该县出产的稻米硒含量普遍比贵州省其它地区高,平均含硒量高于粮食硒的正常含量范围(0.04~0.07μgg-1)。水稻地上各部分含硒量存在差异,糠、秸秆中的含硒量高于糙米,糙米含硒量与土壤硒含量的相关性达极显著水平(r=0.7861*,P<0.05)。     

水稻土中硅磷元素的存在形态及其相互影响研究

采用室内培养试验研究不同施硅和施磷处理对水稻土中硅、磷不同存在形态的影响。结果表明 ,硅磷具有相互促进肥效的关系。施硅影响土壤无机磷的形态 ,硅的施用增加了土壤中Ca2 -P、Al-P和O -P的含量 ,Ca8-P、Ca10 -P变化不明显 ,Fe -P的含量显著降低。其中原因可能是Fe -P在水稻土中活性较高。硅酸钠与硅酸钙相比 ,前者的作用更为明显。施磷影响土壤硅的不同形态 ,磷的施用增加了土壤中水溶性硅和活性硅的含量 ,降低了无定形硅的含量 ,这可能与磷的存在改变了土壤 pH有关     

土壤水分对水稻土和菜园土有机碳分解的影响

采用培养法研究在不同水分条件下水稻土和菜园土有机碳的分解变化特征。结果表明,不同的土壤类型和不同的水分条件下CO2释放速率的变化趋势都是前期分解速率快,后期分解速率减慢并趋于稳定。低土壤水分含量不利于水稻土和菜园土的有机碳分解,中等土壤水分含量有利于菜园土的有机碳分解,高土壤水分含量有利于水稻土的有机碳分解。对有机碳分解累计量曲线的拟合,幂函数(y=b0*xb1)可以很好的反映这种变化趋势,并且b0和b1与土壤水分含量都有很好的相关性。     

长期不同施肥对黄泥土水稳性团聚体颗粒态有机碳的影响

研究了长期不同施肥处理(化肥与秸秆配施、化肥与猪粪配施、单施化肥和不施肥)下太湖地区黄泥土耕层水稳性团聚体颗粒态有机碳含量的变化。结果表明,供试土壤水稳性团聚体组成以>2mm和2~0.25mm粒径为主,施肥下>2mm水稳性团聚体显著增加,并伴随2~0.25mm水稳性团聚体明显减少。颗粒态有机碳主要存在于>2mm水稳性大团聚体中,并随着水稳性团聚体粒径的减小而明显减少。>2mm水稳性大团聚体中的POC对施肥的响应较为敏感,以化肥与秸秆配施下该粒径水稳性团聚体中POC的积累效果最为明显。而化肥与猪粪配施则显著增加了2~0.25mm和0.25~0.053mm水稳性团聚体中的POC含量。土壤不同层次水稳性团聚体中POC的来源不同,在0~5 cm表层可能主要来源于作物根茬生物量,而在5~15 cm土层则可能跟施入的外源有机物有关。