氮肥溶液磁化灌溉下土壤入渗特征和水氮迁移规律研究

Characteristics of Soil Infiltration and Water and Nitrogen Transport under Irrigation with Magnetized Nitrogen Fertilizer Solution

为探明不同浓度氮肥溶液磁化前后土壤入渗特征和水氮迁移规律,采用恒定磁场强度300 mT对质量浓度分别为0、0.4、0.7、1.1 g/L的硝酸钾溶液进行磁化处理,以未磁化处理为对照,测定各处理溶液的电导率、pH值、溶氧量、表面张力、累积入渗量、湿润锋运移距离和入渗后不同土壤剖面水氮迁移分布。试验结果表明:磁化处理溶液溶氧量显著提高,电导率和表面张力显著减小,并随溶液浓度变化有显著影响,但对pH值无显著影响。氮肥溶液磁化入渗增大了相同入渗时间内的湿润锋运移距离和累积入渗量,Philip、GreenAmpt、一维代数入渗模型拟合所得参数土壤吸渗率S、饱和导水率Ks以及有效土壤水扩散率D均增大,湿润峰处的土壤水吸力Sf、土壤水分特征曲线和非饱和导水率综合形状系数m均减小,增渗效果随氮肥溶液浓度增大而增大。磁化氮肥溶液可提高土壤持水能力,且随溶液浓度增大持水能力增强,一维代数入渗公式可较好描述不同磁场强度下各浓度溶液土壤入渗结束时的土壤含水率分布情况。氮肥溶液和磁化作用对土壤硝态氮含量的影响呈显著正相关关系,二者共同作用下,磁化高浓度溶液硝态氮含量最高,这有利于土壤无机氮素的保持。

In order to explore the effects of nitrogen fertilizer solution on soil infiltration characteristics and water and nitrogen migration patterns before and after magnetization,a 300 mT constant magnetic field intensity was used to magnetize different potassium nitrate solution concentrations(0 g/L,0.4 g/L,0.7 g/L and 1.1 g/L),un-magnetized treatments were used as control,and electrical conductivity,pH value,dissolved oxygen amount,cumulative infiltration amount,and wetting front migration distance of solution under different treatments and water and nitrogen migration distribution in different soil profiles after infiltration were determined.The results showed that the amount of dissolved oxygen was significantly increased and electrical conductivity and surface tension were significantly reduced by magnetized fertilizer solution,and the change degree became more significant with the increase of fertilizer solution concentration.The cumulative infiltration amount and the wetting front migration distance within the same time were increased by magnetized fertilizer solution.Soil sorptivity rate S,soil saturated hydraulic conductivity Ks,and effective soil water diffusivity D in the Philip,GreenAmpt,and one-dimensional algebramic infiltration models were increased,while the suction Sf at the wetting peak and the soil moisture characteristic curve and comprehensive shape coefficient of unsaturated water conductivity m were reduced.The effect of increased infiltration was increased with the increase of nitrogen fertilizer solution concentration.The magnetized nitrogen fertilizer solution improved soil water holding capacity and it was increased with the increase of solution concentration.The one-dimensional algebraic infiltration formula could well describe the distribution of soil water content at the end of soil infiltration of each fertilizer solution concentration under different magnetic field intensities.Both the nitrogen fertilizer solution concentration and magnetization had significant positive correlations with soil nitrate content,and magnetized fertilizer solution with high concentration had the highest values under the combined effect which benefited the conservation of soil inorganic nitrogen.