英语翻译Significant corn rooting was not observed below 0.6 m in

英语翻译
Significant corn rooting was not observed below 0.6 m in the Zimmerman fine sand,while corn has been observed to have a rooting depth of 0.90 m (Dowdy et al.,1993).The observation of a shallow root system in this study is a phenomenon that occurred annually from 1993 to 1995,three years with different weather conditions (data not presented).The cause of shallow rooting was the compacted layer.The compacted layer in this soil occurs naturally,in that it was not induced by anthropogenic activities,and is likely glacial in origin.
Corn rooting in this soil was restricted in two ways by the compacted layer.First,the PR of the soil was large enough to restrict rooting by itself (Boone et al.,
1986).Penetration resistance decreased as soil water content increased.However,in this study the soil wa- ter contents needed to reduce PR below the UCML were above field capacity and very rarely occurred in the 0.15–0.35-m layer.The PR profile on 9 Au- gust 1994 (Figure 2) was more representative of the PR throughout the growing season than on 16 Au- gust 1994 (Figure 2) because the soil moisture regime under which PR measurements occurred on 9 Au- gust 1994 was typical throughout the growing season.Thus,PR was limiting corn rooting most of the grow- ing season in the 0.15–0.35-m layer.A compacted layer in this soil was characterized by restrictive PR in combination with high bulk density.
Secondly,the compacted layer changes the mois-
ture regime of this soil,in that slower water movement increased the available water capacity in the 0.15–
0.45-m layer.Irrigation maintained this pool of water
which the crop could quickly access.Profitt et al.
(1985) noted that high-frequency irrigation resulted in shallower rooting systems than low-frequency irriga- tion due to relatively drier soil conditions at greater depths.This compacted layer caused this study’s sup- plemental irrigation to behave more like the high- frequency irrigation treatment in Profitt’ s study be- cause relatively drier soil conditions existed at greater depths.Additionally,Klepper (1990) found that roots extract water preferentially from the upper soil layers before exploiting lower soil depths.Water extraction to 0.75 m could have occurred due to upward water flow into the root extraction zone (sink) that was only 0.60 m deep (Rendig and Taylor,1989).Since there was adequate soil moisture for crop growth in the upper 0.60 m of soil,little water was needed or used from deeper soil layers partly causing a shallow rooting depth.
The irrigation management implications of this compacted zone are important.The soil holds more water than expected based solely on soil texture,so that less supplemental irrigation is needed.However,rooting depth is truncated and available water for irri- gation scheduling must be based on a 0.60-m rooting depth

重要的是玉米生根未见低于0.6米齐默尔曼细砂,而已观察到玉米有一个0.90米深的根（道迪等,1993）.在这项研究中观察到浅层根系的一个现象,就是发生于1993年至1995年3种不同的天气条件下（没有提交数据）.浅生根的原因是压缩层.在这种土壤压实层发生是自然原因造成,因为它不是由人类活动引起的,有可能起源于冰川.
玉米在这片土地生根被两个方面的压缩层限制.第一,土壤pr足够大,以限制自身生根（布恩等.1986）.渗透阻力降低,土壤含水量增加.但是,在这种土壤含水量必须降低,低于UCML公关上述领域的能力并很少在0.15 - 0.35米层发生.在整个种植季节1994年8月9日（图2）比94年8月16日（图2）更具代表,因为1994年8月9日土壤水分测量是在整个生长季节的典型.因此,PR是限制玉米在生长季节生根在0.15 - 0.35米层的主要原因.这个土壤压实层的特点是,限制性体积密度高的组合.其次,压缩层改变了这种土壤水分,因为水的流动速度在0.15 - 0.45米层可用水资源的能力增加了.保持这种作物的灌溉水可以快速通过.Profitt等.（1985年）指出,由于相对干燥的土壤条件,高频在浅水灌溉系统,导致生根比低频灌溉更深入.这夯实层造成这种研究的补充灌溉的行为更像是在Profitt氏研究高频灌溉的学说,因为少雨,存在相对更深入土壤的情况.此外,克莱伯（1990年）发现,从根上提取土壤层,优先在水的下层深度土壤开发.0.75米提取到水可能由于到根提取区（片）,这只是0.60米深（Rendig和泰勒,1989）向上的水流.由于是在作物上0.60米的土壤,土壤水分充足,只需要少量的水或使用较深土层,造成根深.
在这个密集区灌溉的影响是重要的.土壤比预期拥有更多的水完全取决于土壤质地,这样少量的灌溉就够了.然而,根深被截断,用水调度可用于灌溉,必须基于0.60米
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