Which of the following will not increase the efficiency of water use by plants in an irrigation system?
A) the use of herbicides to control weeds
B) the use of drip irrigation for fruit trees
C) the use of crop residues to reduce evaporation
D) the use of concrete-lined delivery ditches
E) the use of flood irrigation for forage crops
Question 2
Humus indirectly affects plant growth through its effects on soil physical and chemical properties, but humic substances have not been shown to affect plant growth processes directly.
Indicate whether the statement is true or false
