鄂南红壤穿透阻力的时空变化研究

为进一步揭示红壤地区季节性干旱的致灾机制,以夏玉米为供试作物,研究鄂南地区季节性干旱过程中,4种耕作措施(深耕、常规耕作、免耕、压实)下,红壤穿透阻力的时空变化特征及其对季节性干旱的响应特点。结果表明:在轻度到中度干旱期间,除深耕外,其余3个耕作措施的耕层红壤穿透阻力均超过了作物根系适宜的最大阻力(2.0 MPa)。红壤穿透阻力在0~40 cm土层呈单峰形分布,且不同耕作措施的峰值大小及峰值位置均存在差异;同时,随土壤含水量的增加,阻力值减小,且峰值位置在土层剖面亦随之发生不同程度的下移。红壤穿透阻力对季节性干旱有较好的响应关系,与耕层土壤含水量的相关系数达–0.839(P0.01),呈极显著非线性负相关关系,以二项式拟合结果最优。该响应关系存在临界反应,当季节性干旱达到一定程度时,土壤含水量较小范围内的变化都将引起红壤穿透阻力的剧烈变化。因此,在红壤地区研究季节性干旱时不可忽视土壤穿透阻力的存在,必须考虑因土壤含水量降低而导致的高土壤阻力对作物的影响。

Temporal and Spatial Response of Red Soil Penetration Resistance in South Hubei

The spatiotemporal variation of soil penetration resistance (PR) and its response characteristics to seasonal drought were studied in order to reveal the disaster mechanism of seasonal drought. Combined with the determination of field and indoor, the spatiotemporal variations of PR were studied under four tillage measures, including deep tillage, conventional tillage, no-tillage and compaction for the summer maize. During the mild and moderate drought, the PR of three tillage measures surpassed the maximum resistance suitable for the root (2.0 MPa) except deep tillage. Soil PR showed unimodal distribution in 0–40 cm soil layer, and the size and position of the peaks were different among tillage measures. With the increase of soil water content, the size decreased and the position went down in soil layer. Soil PR had good response to seasonal drought. The correlation between soil PR and water content was non-linear and negative significantly, with the correlation coefficient of –0.839 and binomial formula. There was a critical response, when seasonal drought reached a certain degree, the violent change of soil PR was caused by water content changed finely. Soil PR was an unneglectable factor in seasonal drought, and the effect of high penetration resistance due to lowered water content on crops must be considered.