Jack McHugh

conservation agriculture soil conservation conservation agriculture principles sustainable farming zero tillage controlled traffic farming irrigation cone penetrometer disc openers seeding people's republic of china water conservation peoples republic of china amelioration plant available water vertisol bulk density hydraulic condcutivity sodics emerald irrgation area salf sirmod water tables deep drainage observation bores cotton farmer training yield adoption gansu cropping zone agronomic benefit wheel tracks weeds residue effect herbicide tillage furrow closing press wheels fertiliser application crop residue management coulters