(一) 红枣、柿子和核桃等这些果树,人们都把它们统称为“铁杆庄稼”,也有些地方把它们分别叫作粮食树和木本油料。确实,它们和一般庄稼——草本庄稼相比,具有很多优点。主要表现在以下四方面: 一、它们的根系很大,可以扎到地下很深的地方,有巨大的抗旱能力。据许多科学家观察证明:果树根系的直径范围大多数大于树冠的直径范围。譬如,枣树的根系一般即可这树冠的二至六倍,垂直根可扎到地下一百七十厘米的深处。因此,不论土壤怎样干旱,都不易影响到它们的正常生长发育。 (I) Fruit trees such as red dates, persimmons and walnuts are collectively referred to as “hardcore crops” and are also sometimes referred to as food trees and woody oil crops. Indeed, they have many advantages over the average crop-herb crop. Mainly manifested in the following four aspects: First, their roots are large, can be tied to a deep underground place, a huge drought capacity. It has been observed by many scientists that most of the diameter of the root system of fruit trees is larger than the diameter of the canopy. For example, the root system of jujube tree can be two to six times the crown, the vertical root can be tied to the ground depth of one hundred seventy centimeters. Therefore, no matter how the soil is dry, it is not easy to affect their normal growth and development.