ABSTRACT

The root system of maize tends to be shallower with plowing tillage than with rotary tilling in upland fields converted from paddy fields. Soil hardness and fertilizer distribution differ between plowing tillage and rotary tilling; thus, we investigated the maize root system at different growth stages with or without fertilizer application in both of these tillage methods. We evaluated the effect of soil hardness on the root system by comparing plowing tillage and rotary tilling in unfertilized plots, and the effect of fertilization by comparing responses to fertilizer application with plowing tillage and rotary tilling since the effects of tillage and fertilization cannot be separated in each tillage method. Root depth index (RDI), which indicates average root depth, was about 20% smaller with plowing tillage than with rotary tilling after the 7th leaf growth stage (V7) in unfertilized plots. Although RDI in fertilized plots was similar or slightly smaller than that in unfertilized plots, the interaction between fertilization and tillage was not significant, except at the tassel formation stage in 2016. Analysis of root distribution indicated that root length density at soil depths of 0–5 cm tended to be higher with plowing tillage than with rotary tilling after V7, but the effect of the interaction between fertilization and tillage was not significant. These results suggest that the root system of maize becomes shallower after V7 with plowing tillage than with rotary tilling mainly due to higher soil penetration resistance in upland fields converted from paddy fields.

摘要

在由稻田转变的旱地中，与旋耕相比，犁耕玉米的根系往往更浅。翻耕与旋耕的土壤硬度和肥料分布不同；因此，我们研究了在这两种耕作方法中施肥或不施肥的不同生长阶段的玉米根系。我们通过比较未施肥地块中的翻耕和旋耕来评估土壤硬度对根系的影响，并通过比较对施肥与翻耕和旋耕的反应来评估施肥的影响，因为耕作和施肥的影响不能分开每种耕作方法。根深指数（RDI），表示平均根深，在未施肥的地块中，在第 7 个叶子生长阶段 (V7) 后，犁耕比旋耕小 20%。尽管施肥地块的RDI与未施肥地相似或略小，但除2016年雄穗形成期外，施肥与耕作的相互作用不显着。 根分布分析表明，土壤深度为0-的根长密度V7后翻耕比旋耕增加5 cm，但施肥与耕作交互作用不显着。这些结果表明，与旋耕相比，V7 处理后玉米的根系变得更浅，这主要是由于从稻田转变为旱地的土壤渗透阻力更高。