狠狠撸

conservation agriculture sustainable farming conservation agriculture principles soil conservation zero tillage controlled traffic farming seeding disc openers cone penetrometer people's republic of china irrigation coulters crop residue management fertiliser application press wheels furrow closing tillage herbicide residue effect weeds wheel tracks 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