Research with nitrogen fertilizer emphasizes fertilize crop—not crop residue

1. Results of field experiments indicate that it is more efficient and effective to apply nitrogen to the crop than to previous crop residues months ahead of planting the crop.

2. The increase in water infiltration rate resulting from various green manures or crop residues was inversely related to the nitrogen content at the time of incorporation. Low-nitrogen residues had a longer-lasting effect than legumes or other high-nitrogen residues.

3. The beneficial effect of barley crop residues on infiltration was significantly reduced by nitrogen application to the residue.

4. Addition of straw, along with fertilizer nitrogen, greatly reduced the uptake of fertilizer nitrogen by the succeeding crops.

5. The time required for cycling fertilizer nitrogen through the soil organic fraction and back into available form apparently involves a matter of years, or perhaps decades, rather than weeks or months.

6. Fine shredding and early incorporation of crop residues into a moist soil are key factors in handling residues to avoid interference with planting operations.