铵、钾同时存在时, 土壤对铵的优先吸附

The water stability of aggregates in various size classes separated from 18 samples of red soils under different managements, and the mechanisms responsible for the formation of water-stable soil aggregates were studied. The results showed that the water stability of soil aggregates declined with increasing size, especially for the low organic matter soils. Organic matter plays a key role in the formation of water-stable soil aggregates. The larger the soil aggregate size, the greater the impact of organic matter on the water stability of soil aggregates. Removal of organic matter markedly disintegrated the large water-stable aggregates (> 2.0 mm) and increased the small ones (< 0.25-0.5mm) to some extent, whereas removal of free iron(aluminium) oxides considerably destroyed aggregates of all sizes, especially the < 0.25-0.5 mm classes. The contents of organic matter in water-stable aggregates increased with aggregate sizes. It is concluded from this study that small water-stable aggregates (< 0.25-0.5 mm) were chiefly cemented by Fe and Al oxides whilst the large ones (> 2.0 mm) were mainly glued up by organic matter. Both free oxides and organic matter contribute to the formation and water stability of aggregates in red soils.     

江西九江地区第四纪红粘土上的“黄帽子”

A thin layer of yellow-brown-colored earth was generally found on Quaternary red clay in Jiujiang, Jiangxi Province. A typical profile was established. Both particle size distribution and REE (rare earth elements) characteristics of the yellow-brown-colored earth of the profile fully suggested its aeolian origin and close similarity to Nanjing Xiashu loess. The study also implied aeolian origin of the underlying Quaternary red clay. Compared with the red clay, the yellow-brown-colored earth was less weathered because of its lower content of free iron and higher mole ratios of SiO₂/Al₂O₃ and SiO₂/(Fe₂O₃+Al₂O₃) as well as its less developed chemical microtextures of quartz grains. In order to study the ages of the two deposits comparatively, the thermoluminescent dating method was used. As a result, the bottom of the yellow-brown-colored earth was dated to 60±5 ka B. P. and the upper part of the red clay 388±54 ka B. P. It was suggested that the yellow-brown-colored earth was formed in the Late Pleistocene and was probably the aeolian deposit of the Last Glacial, which corresponded with the Malan loess in the Loess Plateau of the northwestern part of China; while the underlying red clay was formed in the Middle Pleistocene. A "yellow cap" on Quaternary red clay in Jiujiang implied a great climatic and environmental variation in the beginning of the Late Pleistocene in the southern part of China, especially in the middle and lower reaches of the Yangtze River. The event not only halted the rubification, once dominating the region, but also produced a widespread covering of aeolian deposit, as only occurred in the cold and dry environment.     

低丘红壤有机碳库的密度及变异

在中国科学院红壤生态实验站,采样分析了不同利用方式下土壤有机C 库的密度及其变异。结果表明,低丘红壤有机C 的密度0 ~ 20cm为(2.09 0.69) kg/m2,0 ~ 100 cm为(5.01 1.46) kg/m2; 全N密度0 ~ 20 cm为(0.20 0.07) kg/m2, 0 ~ 100 cm为(0.59 0.14) kg/m2。从裸地到稀疏荒草地,0 ~ 20 cm和0 ~ 100 cm土壤有机C 密度可以提高1.0 kg/m2和1.7 kg/m2;而从稀疏荒草地到人工林地或园地,0 ~ 20 cm和0 ~ 100 cm土壤有机C 密度可以提高0.7 kg/m2和0.9 kg/m2;稀疏荒草地如果开垦利用为水田,经长期培肥达到高度熟化,则0 ~ 20 cm和0 ~ 100 cm土壤有机C 密度可以提高2.3 kg/m2和4.4 kg/m2。即使不同类型的人工林地和园地之间,0 ~ 20 cm和0 ~ 100 cm土壤有机C 的密度差异也可达到1.0 kg/m2和3.5 kg/m2。不同地形部位之间0 ~ 20 cm和0 ~ 100 cm土壤有机C 密度差异达到1.3 kg/m2和2.9 kg/m2,全N密度差异达0.1 kg/m2和0.3 kg/m2;不同肥力水平之间0 ~ 20 cm和0 ~ 100 cm土壤有机C 密度差异达到1.5 ~ 2.2 kg/m2和2.8 ~ 4.1 kg/m2,全N密度差异达0.07 ~ 0.11 kg/m2和0.20 ~ 0.23 kg/m2; 强烈侵蚀可以降低0 ~ 20 cm和0 ~ 100 cm土壤有机C 密度1.4 kg/m2和2.2 kg/m2。因此,通过调整土地利用方式,可以提高土壤有机C 库密度,增     

侵蚀型红壤植被恢复后土壤养分含量与物理性质的变化

为了解侵蚀型红壤植被恢复后土壤养分含量与物理性质的变化状况,采集了植被恢复17年和9年的两个定位试验点土壤样品。分析结果表明：侵蚀型红壤植被恢复后土壤养分含量明显增加。恢复17年的木荷、杉木林0～0．2m土层土壤全氮和有机质含量分别比对照增加了3．92倍、2．96倍、5．80倍和3．52倍,土壤有效养分中土壤有效磷含量增加幅度最大。植被恢复后土壤物理性质得到极大改善．表现在土壤容量明显降低,土壤总孔度、通气孔度增加和大于1mm大团聚体与大于0．25mm水稳性团聚体总量的增加。总的来看,恢复17年的木荷和恢复9年的黑麦草两处理．土壤物理性质改善最为明显．此两处理0～0．2m表层土壤容量比对照区降低了27．9％和20．41％,大于0．25mm水稳性团聚体总量分别比对照区增加了31．09％和29．96％,土壤总孔度和通气孔度分别是对照区的1．34倍、1．25倍、2．59倍和2．14倍。     

高接在不同基砧的锦橙上的华红脐橙的栽培表现及矿质营养含量年变化

田间调查了高接在两种不同基砧的锦橙上的华红脐橙的栽培表现及矿质营养含量年变化差异。结果表明,在栽培效应上,红桔基砧树体生长较旺,投产晚,果实小,果实含酸量较高、糖酸比较低,出汁率和Vc含量较高;枳基砧则相反。在矿质元素含量年变化上,不同基砧树的叶片矿质元素含量年变化趋势除Mn、Zn外,其它元素含量年变化趋势差异明显;不同基砧根系的各种矿质元素含量年变化趋势基本相似;在不同基砧树之间,除根系Mg、Fe含量外,叶片和根系的各种矿质元素含量在年周期内的差异明显。     

中国东南部红壤地区不同植被对土壤侵蚀和土壤养分的影响

The effect of different vegetation systems including bamboo plantation (BP), forest ecosystem (CF), citrus orchard (Ctr) and farmland (FL) on erosion and nutrients of red soil were investigated in hilly region of southeastern China to find effective control measures for soil erosion. The results showed that all the vegetation systems could significantly reduce soil erosion and nutrient losses compared to bare land (Br). The ability of different vegetation systems to conserve soil and water was in the order of Ctr > BP > CF > FL > Br. Vegetation could also improve soil fertility. The soil organic matter, total N and total P contents were much higher in all the vegetation systems than in bare land, especially for the top soils. Vegetation systems improved soil physical properties remarkably. Compared to the bare land, soil organic matter, TP, TK and available K, especially soil microbial biomass C, N and P, increased under all the vegetation covers. However, they were still much lower than expected, thus these biological measurements are still needed to be carried out continuously.     

红壤坡地雨水产流及其土壤流失的垫面反应

通过4年(1998～2001年)径流场定位观测研究,探明了不同植被垫面雨水产流过程中系统水土流失有显著性差异。水流失量为农作区>常绿灌木区、针叶林区>常绿果园区>退化区、恢复区。坡地不同垫面间雨水地表径流的差异存在,为坡地雨水利用和利用坡地集雨支持农田灌溉提供了依据和可调控性。土壤流失量受人为干预、耕作强度的影响很大,坡地从自然保护到作物栽培,系统的土壤流失量提高20倍。茶果林地的土壤流失低于作物耕种的2～3倍,而高于自然利用和自然保护的6～12倍。养分流失在数量和质量上皆取决于垫面构成。提出了利用坡地集雨优势,构建与单元生态系统水循环平衡相适应的坡地农林复合生态系统,并通过水平衡生态建设来维系生态系统的水分平衡。     

坡地赤红壤不同利用模式对土壤磷和酶的影响

试验采用广东东莞花岗岩发育的坡地赤红壤为样品进行研究表明 :在坡地赤红壤的 4种利用模式中 ,旱地种植花生 ,荔枝可以有效地改善土壤的酸性 ,提高土壤肥力 ;提高土壤Al-P和Fe -P的含量 ,减少O -P的所占的比例 ,提高坡地赤红壤磷酸盐的有效性 ;增加土壤表层的脲酶和蛋白酶的活性 ,可能使土壤的磷酸酶的活性降低     

龙眼复合涂膜保鲜剂的研究

选用魔芋葡苷聚糖、壳聚糖、乳化剂等，采用正交设计设立10个试验组，进行涂膜效果试验和龙眼常温保鲜试验，得出最佳的涂膜配方(含抗菌抑霉剂)为：魔芋葡甘聚糖浓度0.2%，壳聚糖0.2%，蔗糖脂肪酸脂0.15%。经过重复性试验，采用该组配方涂膜能有效增加“福眼”在贮藏期间的好果率，在常温下贮藏7d好果率为82%。显微照片显示，复合涂膜能在龙眼果皮形成一层更加致密的白色半透膜，能渗透到龙眼外果皮的微裂孔和维管束中，覆盖龙眼果皮表面的细孔。     

稻草覆盖对坡地红壤培肥及作物增产的效果

研究了坡地红壤连续5年采用稻草覆盖措施对土壤肥力和作物产量的影响。结果表明,“稻草+化肥氮磷”(“Straw+NP”)处理的土壤有机碳和全氮、磷分别比不施肥(CK)的提高42.9%和17.4%、44.2%,有机碳和全氮的增幅约是纯化肥(NPK)处理的2倍。与CK和NPK处理的相比,“Straw+NP”处理能明显提高微生物生物量碳、氮、磷和溶解性有机碳、氮以及Olsen-P含量,差异达到显著(P<0.05)或极显著(P<0.01)水平。在等养分施用量的条件下,“Straw+NP”处理能显著提高油菜和甘薯的产量。因此,稻草易地覆盖是一种有效培肥坡地红壤和增加作物产量的途径。