An Early Source of Phosphorus for Agriculture Was ________

Q13: More nitrogen is fixed by lightning than

Q14: Uptake of potassium ions from the soil

Q15: As the LD₅₀ of a substance decreases,the

Q16: All of the following are natural organic

Q17: Which of the following would be a

Q19: Which is classified as a narrow spectrum

Q20: Which of the following is an herbicide?<br>A)2,4-D<br>B)parathion<br>C)carbaryl<br>D)diazinon

Q21: Organophosphorus pesticides are generally less _ than

Q22: The LD₅₀ for aldicarb in rats is

Q23: Which of the following statements about humus