Cotton root growth can be affected by different nitrogen fertilizer rates. The objective of the present study was to quantify the effects of nitrogen fertilization rate on cotton root growth and distribution using minirhizotron and soil coring methods. A secondary objective was to evaluate the minirhizotron method as a tool for determining nitrogen application rates using the root distribution as an index. This study was conducted on a Bt cotton cultivar (Jimian 958) under four nitrogen fertilization rates, i.e., 0, 120, 240 and 480 kg ha-1 (control, low, moderate and high levels, respectively), in the Yellow River basin of China from 2013–2015. The sampling process, details of each method as well as the root morphology and root distribution were measured. The operational processes, time and labor needed for the soil core method were all greater than those for the minirhizotron method. The total root length density and the length density in most soil layers, especially in the upper soil layers, first increased but then decreased as nitrogen fertilization increased, and the same trend was observed for both methods. Compared with N0, the total root length density under moderate nitrogen fertilization by the soil coring method increased by more than 94.82%, in 2014 and 61.11% in 2015; while by the minirhizotron method the corresponding values were 28.24% in 2014 and 57.47%, in 2015. Most roots were distributed in the shallow soil layers (0–60 cm) in each method. However, the root distribution with the soil coring method (>73.11%) was greater than that with the minirhizotron method (>47.07%). The correlations between the root morphology indexes of shallow soil depth measured using the two methods were generally significant, with correlative coefficients greater than 0.334. We concluded that the minirhizotron method could be used for cotton root analysis and most cotton roots distributed in upper soil layers (0-60cm). In addition, a moderate nitrogen rate (240 kg ha-1) could increase root growth, especially in the shallow soil layers. The differences observed with the minirhizotron method were clearer than those observed with the soil coring method.
展开▼
机译：不同氮肥用量会影响棉花根系生长。本研究的目的是使用微型根瘤菌和土壤取芯方法来量化氮肥施用量对棉花根系生长和分布的影响。第二个目的是评估微根管法作为一种以根系分布为指标确定氮施用量的工具。这项研究是在Bt棉花品种（吉棉958）上以4种氮肥的施肥速率进行的，即0、120、240和480 kg ha -1 （分别为对照，低，中和高水平） ），2013-2015年在中国黄河流域。测量了采样过程，每种方法的详细信息以及根的形态和根分布。土芯法所需的操作过程，时间和劳力都比微型根管法大。在大多数土壤层中，特别是在上部土壤层中，总根长密度和长度密度先随氮肥施用量的增加而增加，然后减少，并且两种方法都观察到相同的趋势。与N0相比，土壤去芯法适度施氮的总根长密度在2014年和2015年分别增加了94.82％和61.11％； 2014年和2015年的根瘤菌对应值分别为28.24％和57.47％。每种方法中，大多数根系分布在浅土层（0-60 cm）中。然而，土壤去核法（> 73.11％）的根部分布大于微型根部放牧法（> 47.07％）的根部分布。两种方法测得的浅层土壤根部形态指标之间的相关性通常很显着，相关系数大于0.334。我们得出的结论是，微根管方法可用于棉根分析，大多数棉根分布在上层土壤层（0-60cm）中。此外，适度的氮肥施用量（240 kg ha -1 ）可以促进根系生长，尤其是在浅层土壤中。用微型根管法观察到的差异比用土壤取芯法观察到的差异更明显。
展开▼
