[问答题] 确定植物必需营养元素的三条标准是什么？

种实调拨 下列井控装备，（）是井控管汇。 ["节流管汇","压井管汇","放喷管线","套管头","下旋塞"] We hereby register a claim with you（）the basis of here,we can obtain a number of orders for you. 下列井控装备，（）是内防喷工具。 ["节流管汇","浮阀","箭形止回阀","方钻杆下旋塞","方钻杆上旋塞"] 粗煤气净化包括哪四个步骤？ 确定植物必需营养元素的三条标准是什么？