Potassium Status and Fertility Evaluation of Major Upland Soils in Northeastern Part of China

Potassium status and fertility of major upland soils of the northeastern part of China was evaluated for soils collected at Jilin and Liaoning provinces, covering Meadow soil, Black-colored soil, Dark-brown forest soil, Sols lessives, and Saline soil which occupy more than 80% of the upland field. Total and mineral K contents ranged from 21.1 to 25.8 and from 20.6 to 25.0 g kg^-1, respectively. Mineral K occupied 92 to 99% of the total K and its main source was estimated to be K-feldspars, based on the significant and positive correlation between mineral K and sand contents. Nonexchangeable K was measured by extraction with hot 1MHNO_3 for 10 min, and its content was in a range of 264 to 971 mg kg^-1, occupying 1 to 4% of total K. Content of nonexchangeable K was significantly and positively correlated with mica and clay contents. Content of exchangeable K, including water-soluble K, was ranged between 66 and 974 mg kg^-1 and occupied 0.3 to 4 % of total K. It was highly significantly and positively correlated with cation-exchange capacity and organic matter content. Potassium fertility of upland soils was roughly evaluated based on the contents of nonexchangeable and exchangeable K. It was in the order of eastern>central>western agricultural divisions for soils in Jilin province and lowest for a soil in Liaoning province, and in the order of Black-colored soil>Meadow soil >Sols lessives, Dark-brown forest soil for soils in the eastern division of Jilin province. Potassium fertility was controlled first by the mica content which is mainly derived from eolian dust from inland China and Mongolia, and by contents of 2:1 mixed-layer minerals, through contribution to cation-exchange capacity, and of organic matter.中国東北部主要畑土壌の全カリウム含量と鉱物カリウム含量は,それぞれ21.1～25.8g kg^- 1, 20.6～25.0g kg^-1の範囲にあり,農業地域と土壌型による大きな差はみられなかった.鉱物カリウムは全カリウムの92～99%を占め,主な給源はカリ長石と推測された.交換態カリウム含量は66～974mg kg^-1の範囲にあり,全カリウム含量の0.3～4%を占めた.交換態カリウム含量は,農業地域間では吉林省東部地区>中部地区,遼寧省>吉林省西部地区の順に低く,吉林省東部地区の土壌型問では湿草地土,黒土>暗棕壌,レシベ土の順に低かった.緩効態カリウム含量は264～971mg kg^-1の範囲にあり(全カリウム含量の1～ 4%), stepカリウム含量と合わせて,農業地域別では吉林省東部地区≧中部地区,西部地区>遼寧省の順であり,吉林省東部地区の土壌型でみれば,黒土≧湿草地土≧レシベ土,暗棕壌の順であった.緩効態およびstepカリウムの給源として雲母粘土鉱物の縁辺部のカリウムが推測された.交換態,緩効態, stepカリウム含量の総体としてのカリウム肥沃度は,農業地域別では吉林省東部地区>中部地区>西部地区〉遼寧省の順,吉林省東部地区の土壌型間では黒土>湿草地土>レシベ土,暗棕壌の順にあると推論された.中国東北部畑土壌の雲母は中国内陸部やモンゴルからの風成塵の寄与を強く受けており,風成塵は中国東北部畑土壌のカリウム肥沃度に大きな影響を与える.カリウム肥沃度を規定する要因は,雲母含量と,陽イオン交換容量を通して関与する粘土含量と2: 1型混合層鉱物含量であり,さらに有機物含量である