红松幼苗根际微区pH与N、P、K的梯度分布

采用水平根垫法对2年生红松幼苗进行栽培实验,应用冰冻薄层切片法对距幼苗根面不同距离的土壤进行分层取样,并测定不同层次土壤中pH与有效N、P、K的含量.结果表明,距红松幼苗根面不同距离的土壤中,pH与有效N、P、K均呈有规律的梯度分布,即根际微区pH较土体下降,且距根面越近,pH越低;有效N在根际出现较大的亏缺区,亏缺范围为距根表10 mm以内,最大亏缺率位于距根面5 mm处,而在紧靠根面的土壤中与最大亏缺率相比出现N素的相对累积;有效P在根际土壤中只存在明显的亏缺区,亏缺范围为距根面6 mm以内,距根面0-1 mm亏缺率最大,达30%左右;近根面土壤中有效K浓度出现累积,主要累积范围为距根面0-2 mm,最大累积率约34%,但在距根面4-7 mm又呈现一定程度的亏缺.

Gradient distribution of the pH and available N, P, and K in the rhizosphere soil of Pinus koraiensis seedlings

Two years old seedlings of Pinus koraiensis were planted in pots with horizontal root-mat treatment.Soil samples were stratified collected by thin slicing the rhizosphere soil along the distance from the root plane of seedlings,and the pH value and(available nitrogen(N),phosphorus)(P),and potassium(K) contents were determined.The results showed that there existed a special gradient distribution of the pH and the contents of N,P and K along the distance from the root plane of the seedlings.The pH decreased in the rhizosphere soil compared with the bulk soil and increased gradually and reached its background value in the bulk soil.There was a wide depletion zone of soil available N near the root plane.The biggest depletion ratio of available N occurred at the site 5 mm from the root plane,whereas there existed a relative accumulation at the place 01 mm from the root plane in contrast with the biggest depletion ratio.For the available P,there only existed a obvious depletion zone,and the biggest depletion ratio(30%) existed at the place 0-1 mm from the root plane.There was a accumulation of soil available K at the distance of 0-2 mm from the root plane,while a depletion zone occurred at the site 4-7 mm from the root plane in contrast with the bulk soil.