高产栽培条件下种植密度对不同类型玉米品种根系时空分布动态的影响

以平展大穗型品种鲁单981 (LD981)和紧凑中穗型品种鲁单818 (LD818)，比较研究了不同种植密度下根系时空分布动态，以期为玉米品种的选育和高产栽培提供理论依据。结果表明, 随生育进程，2个品种的根系总体积、总表面积、活跃吸收面积与总干重均呈先升后降趋势，多为开花期至乳熟期达最大。随种植密度递增，LD981和LD818的根层数与数量、总体积、总表面积、活跃吸收面积以及水平与垂直方向各分布区域的干重均呈递减趋势，LD981的递减速率明显大于LD818。生育期内，不同种植密度下LD981和LD818的根系干重水平方向0~6 cm、6~12 cm和12~18 cm分布表现为高密度区、中密度区和低密度区; 垂直方向0~20 cm、20~40 cm、40~60 cm和60~80 cm土层分别表现为高密度层、中密度层、低密度层和稀密度层; LD981水平方向0~6 cm范围根系干重所占比例比LD818的低2.96%，6~18 cm则高14.33%，垂直方向0~40 cm土层根系干重所占比例前者比后者高3.71%，40~80 cm土层则低35.97%。本研究说明不同类型玉米品种对根系伸展空间方向和大小的要求存在差异，平展大穗型品种LD981单株根量多，吸收能力强，根系分布较浅，对种植密度递增导致的水平方向空间受限制的反应更为敏感，宜适当增大株距稀植; 紧凑中穗型品种LD818单株根系呈现“横向紧缩，纵向延伸”的特点，更能适应随着种植密度递增导致的水平方向空间受限制的“拥挤”，宜适当减小株距密植。

Influence of Planting Density on Root Spatio-Temporal Distribution of Different Types of Maize under High-Yielding Cultivation Conditions

A field experiment was conducted to compare the influence of planting density onthe root spatio-temporal distribution using two types of maize cultivar (LD981, a planophile massive ear type variety, and LD818, an erectophile middle ear type variety) under high-yielding cultivation conditions. The results indicated that the total root volume (TRV), total root-absorbing area (TRAA), active-absorbing area (AAA), and total root dry weight (TRDW) of the both maize varieties increased at first and then decreased during the growing stages. From the flowing stage to the milking stage, the above parameters reached their maximum values. The number of root layers, root number, TRV, TRAA, AAA, and TRDW decreased with the increase of planting density, but the rate of decrease in LD981 was higher than that in LD818. In the horizontal distribution, 0–6, 6–12, and 12–18 cm from the stem were classified as higher, mid, and lower root density zones, respectively; in the vertical distribution, 0–20, 20–40, 40–60, and 60–80 cm below the ground surface were classified as higher, mid, lower, and thinner root density layers, respectively. In the horizontal distribution, the percentage of root dry weight in 0–6 cm soil from the stem of LD818 was higher (2.96%) than that of LD981, but lower (14.33%) in 6–18 cm soil; in the vertical distribution, the percentage of root dry weight in 0–40 cm soil below the ground surface in LD818 was lower (3.71%) than that in LD981, but higher (14.33%) in 40–80 cm soil. The results of this study suggest that the requirement in root distribution space and orientation is different among different maize varieties. LD981 posses more roots mainly distributing in lower soil layers. LD981 is more sensitive to horizontal restriction owing to higher planting density, and suitable to be planted under lower planting density condition. LD818 shows the root distribution characteristics of “vertical extension and horizontal contraction”, adapting horizontal restriction owing to higher planting density, suitably cultivating under higher planting density condition.