Effect of nitrate leaching of winter wheat field based on straw application in the Yellow River irrigation area of Ningxia Effect of swine manure application on nitrate leaching in winter wheat field in the Yellow River irrigation area of Ningxia, China. Concentration change and migration characteristics of nitrogen in the paddy field of Ningxia Yellow River Irrigation Area Influence of simulated rotational grazing on the forage production of spring wheat, oats and rye in the Yellow River irrigation area