The nitrogen requirement in the utilization of carbonaceous residues in soil
1946
Pinck, L.A. | Allison, F.E. | Gaddy, V.L.
Greenhouse experiments, planned to determine how carbonaceous crop residues can best be utilized without composting and how much nitrogen is inactivated by a unit weight of carbon, are reported. The main results are as follows: 1. Under winter greenhouse conditions, sufficient nitrogen had to be added to make the carbon-nitrogen ratio of a straw-urea mixture about 35 in order to avoid injury by the straw. This corresponds to a nitrogen content of 1.2% for the dry organic matter. Under spring and summer conditions, the corresponding values were 27 to 31 for the carbon-nitrogen ratio and 1.56 to 1.37 for the nitrogen percentage. 2. Additions of nitrogen above that required to meet the needs of soil flora produced essentially a linear effect on the total nitrogen content of the harvested crops; the increase in yields of dry matter, however, decreased with successive increments of added nitrogen. There was no evidence of any injury due to straw other than its on nitrogen availability. A 6-weeks' delay in the planting of the crop resulted in a slightly lower recovery of the added nitrogen, but essentially none of this could be attributed to the straw. The residual crops of Sudan grass removed only small quantities of nitrogen even though the highest percentages of the added nitrogen removed by the first crop in the two experiments were only 47 and 55, respectively. 6. The experiments indicate that by using adequate quantities of commercial nitrogen, undecomposed carbonaceous crop residues can be utilized advantageously for soil organic matter maintenance without injury to crops.
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