基于棉田原位高光谱数据的土壤pH值反演与制图研究

[目的] 研究快速、准确大面积监测农田土壤pH值,为大面积土壤改良和实现农田精细化管理提供科学支持。[方法] 以南疆阿拉尔市十二团棉田为研究区,采用网格采样法采集231个样点的原位高光谱数据,并同步采集其中116个样点的土壤样品;分析了原位高光谱反射率数据经不同预处理模式后的光谱数据与土壤pH值的相关性;采用偏最小二乘回归、支持向量机回归和随机森林3种建模方法分别建立了土壤pH值的高光谱反演模型,根据模型评价指标优选出最优模型对未采集土壤样点的pH值进行反演制图。[结果] 反射率经微分处理后可有效改善其与土壤pH值的相关性;反射率二阶微分的随机森林模型为所有模型中的最优模型,其验证集的R²为0.87,RMSE为0.04,RPD为2.53;最优模型反演的pH值数据插值所得数字图与实测pH值插值图的空间分布特征高度吻合,能客观反映土壤碱化的空间分布状况。[结论] 随机森林模型为原位反演南疆棉田土壤pH值的最优模型,克里金插值能够客观可视化表达研究区土壤pH值的分布状况。     

Comparing two theories about the nature of soil phosphate

Two theories about the nature of phosphate in soil are current. One holds that soil phosphate is mostly present as particles of iron, aluminium and calcium phosphates: the precipitate-particulate theory. The other holds that phosphate is mostly adsorbed and penetrates heterogeneous, variable-charge particles: the adsorption-penetration theory. This is the only theory that is consistent with and can be deduced from observations. It is my contention that the persistence of the precipitate-particulate theory leads to: wasted research effort in trying to identify the supposed phosphate fractions; failure to recognize the long-term changes in soil phosphate due to repeated applications, and thus to over-fertilisation; and misapprehension about the effects of pH on phosphate availability.     

Soil pH Dynamics and Nitrogen Transformations Under Long-Term Chemical Fertilization in Four Typical Chinese Croplands

Long-term fertilization experiment provides the platform for understanding the proton budgets in nitrogen transformations of agricultural ecosystems. We analyzed the historical （1990-2005） observations on four agricultural long-term experiments in China （Changping, Chongqing, Gongzhuling and Qiyang） under four different fertilizations, i.e., no-fertilizer （control）, sole chemical nitrogen fertilizer （FN）, sole chemical phosphorous and potassium fertilizers （FPK） and chemical nitrogen, phosphorous and potassium fertilizers （FNPK）. The significant decline in topsoil pH was caused not only by chemical N fertilization （0.29 and 0.89？pH at Gongzhuling and Qiyang, respectively） but also by chemical PK fertilization （0.59？pH at Gongzhuling）. The enhancement of available nutrients in the topsoil due to long-term direct nutrients supply with chemical fertilizers was in the descending order of available P （168-599%）〉available K （16-189%）〉available N （9-33%）. The relative rate of soil pH decline was lower under long-term judicious chemical fertilization （-0.036-0.034 ？pH yr-1） than that under long-term sole N or PK fertilization （0.016-0.086 ？pH yr-1）. Long-term judicious chemical fertilization with N, P and K elements decreases the nutritional limitation to normal crop growth, under which more N output was distributed in biomass removal rather than the loss via nitrate leaching. We concluded that the N distribution percentage of nitrate leaching to biomass removal might be a suitable indicator to the sensitivity of agricultural ecosystems to acid inputs.     

辽东山区次生林生态系统不同林型树干茎流的理化性质

为明确森林对降雨水质的影响,于2011年6-8月,对辽东山区次生林生态系统5种主要林型:落叶松人工林(Larix olgensis)(Lo)、花曲柳林(Fraxinus rhynchophulla)(Fr)、杂木林(Mb)、红松人工林(Pinus koraiensis)(Pk)和蒙古栎林(Querus mongolica)(Om)中树干茎流和林外雨理化性质进行了监测。与林外雨相比,5种林型树干茎流均出现明显酸化(P<0.05),酸化程度为:Pk > Lo > Fr> Om > Mb;各林型树干茎流的电导率、总溶解固体含量、氯离子浓度、硝酸根离子浓度、铵根离子浓度浓度和总磷浓度显著升高(P<0.05),溶解氧浓度明显下降(P<0.05)。林型间相比,Lo与Pk的电导率和总溶解固体含量和Lo的氯离子浓度较高;Lo和Pk的硝酸根离子浓度和总磷浓度明显低于其它林型(P<0.05);Mb的硝酸根离子浓度和总磷浓度显著高于其它林型(P<0.05)。各林型树干茎流的硝酸根离子浓度和胸径与树高的乘积呈显著正相关。上述结果主要受降雨因素(降雨前干沉降时间长度等)、林分特征(叶面积指数、树皮特征)、树木枝叶表层积累物质的理化性质等影响。结论:各林型树干茎流水质均明显下降,其中Mb树干茎流对雨水化学性质影响较大;Pk和Lo树干茎流水体纯度下降最为显著。     

土壤氧气可获得性对双季稻田温室气体排放通量的影响

为探讨土壤氧气可获得性(SOA)对双季稻田温室气体排放的影响,利用静态箱气相色谱法对多种管理措施影响下稻田温室气体排放通量和土壤氧化还原电位(Eh)、pH值及田间淹水深度(H)等3种SOA因子进行了观测。结果表明,甲烷(CH₄)排放最集中的Eh值、pH值和H范围分别为-100-0mV、5 < pH < 6和1-5cm,3个范围内分别观测到48.8%、61.1%和77.0%的CH₄排放,其中H对CH₄排放影响最明显,单独由其就可解释37.8%的CH₄排放通量(P < 0.0001)。对于氧化亚氮(N₂O),观测到较多的负通量,其纯排放最密集的3种SOA因子的范围分别是:0-100mV、5 < pH < 6和1-5cm,而200-300mV是其排放的临界Eh范围,高于此范围N₂O排放极少。厌氧的反硝化过程是双季稻田N₂O产生的主导过程。可为水稻田温室气体排放机理研究提供基础数据。     

土壤pH对富士苹果生长及碳氮利用特性的影响

 以2年生富士（Malus × domestica Borkh.‘Red Fuji’）/平邑甜茶（Malus hupehensis）为试材,采用碳氮双标记技术,研究了6个不同土壤pH处理（pH 6.83、6.40、5.87、5.29、4.58和3.82）对植株生长及碳氮利用特性的影响。研究结果表明：苹果植株根系、地上部、植株总干质量、根冠比、叶片净光合速率和¹⁵N利用率均随土壤pH的降低而降低,且土壤pH越低降低幅度越大。各器官的¹⁵N和¹³C分配率在不同土壤pH处理间呈现相同的变化规律：叶最多,其次是1年生茎,然后是根,最少为2年生茎。同一器官不同土壤pH处理间¹⁵N和¹³C分配率存在差异,以根和叶最为显著;随土壤pH的降低,叶中的¹⁵N和¹³C分配率逐渐升高,而根中的¹⁵N和¹³C分配率则逐渐降低。     

Influence of Lime and Gypsum on Growth and Yield of Upland Rice and Changes in Soil Chemical Properties

Upland rice is an important crop in the cropping systems of South America, including Brazil. Two greenhouse experiments were conducted to determine influence of lime and gypsum on yield and yield components of upland rice and changes in the chemical properties of an Oxisol. The lime rates used were 0, 0.71, 1.42, 2.14, 2.85, and 4.28 g kg^?1 soil. The gypsum rates were 0, 0.28, 0.57, 1.14, 1.71, and 2.28 g kg^?1. Lime as well as gypsum significantly increased plant height, straw and grain yield, and panicle density in a quadratic fashion. Adequate lime and gypsum rates for maximum grain yield were 1.11 g kg^?1 and 1.13 g kg^?1, respectively. Plant height, straw yield, and panicle density were positively related to grain yield. Lime as well as gypsum application significantly changed extractable calcium (Ca), magnesium (Mg), hydrogen (H)+aluminum (Al), base saturation, and effective cation exchange capacity. In addition, liming also significantly increased pH, extractable phosphorus (P) and potassium (K), calcium saturation, magnesium saturation, and potassium saturation. Optimum acidity indices for the grain yield of upland rice were pH 6.0, Ca 1.7 cmol_c kg^?1, base saturation 60%, and calcium saturation 47%. In addition, upland rice can tolerate 42% of acidity saturation.     

木醋及松针对越橘栽培土壤改良的影响

越橘(Vaccinium uliginosum L.)栽培中对土壤条件要求较高,需有机质含量高的强酸性土壤。为解决土壤的限制,在"美登"和"北陆"两个品种的栽培土壤中添加木醋及松针,测定株高、土壤pH、土壤速效氮磷钾及有机质含量、土壤微生物数量来研究木醋和松针对越橘栽培土壤的改良作用。结果表明:各处理株高与对照均产生了显著性差异。处理C(田园土︰松针=3︰1+木醋20 ml/盆)植株最高,美登和北陆比对照分别增加了19.0 cm和14.6 cm。处理D(田园土︰松针=3︰1+木醋30 ml/盆)pH降低最大,美登和北陆分别为4.87和4.73。随着木醋使用量的增加,土壤速效氮含量出现先升后降的现象,美登和北陆速效氮含量比对照增加最大量分别为29.6 mg/g和69.6 mg/g。木醋使用量越大,速效磷含量越高。美登和北陆速效磷最大含量比对照分别增加了88.8 mg/g和78.0 mg/g。速效钾含量的增加,松针作用显著,木醋作用不显著。"美登"处理C和"北陆"处理D土壤有机质含量最高,分别为47.0 g/kg和55.0 g/kg。木醋的不同添加量对土壤微生物可以起到不同的调控作用。土壤中细菌的数量变化较大,放线菌和真菌数量变化较小。木醋及松针满足了越橘对土壤低pH及高含量有机质的特殊需求,对越橘栽培土壤起到了一定的改良作用。     

1984年以来广东水稻土pH变化趋势及影响因素

利用广东省1984年以来的长期定位监测数据,对全省20多年来的水稻土pH变化趋势进行了分析。结果表明:1984年以来,全省水稻土整体呈现明显的酸化趋势,期间水稻土pH下降了0.33单位,强酸和酸性土壤的分布频率呈明显的上升趋势,分别增加了3.2%和21.9%;珠三角地区的水稻土pH下降了0.54单位,明显高于其他区域。单施化肥使土壤pH降低,而长期坚持化肥结合有机肥施用可以提高土壤抵抗酸化的能力,提高水稻土pH。重化肥而轻有机肥是导致广东省水田土壤pH下降的主要原因,同时日益严重的酸雨也是加速土壤pH下降的重要因素。今后应重视施用有机肥,减缓水稻土的酸化进程。