Influence of phosphorus deficiency of the soil on the protein content of alfalfa
1945
Alway, F.J. | Nesom, G.H.
Nitrogen determinations are reported on 61 pairs of samples collected from 52 western Minnesota fields of alfalfa that showed an outstanding response to phosphates, only part of each field having been fertilized. In 37 of the comparisons, the N content of the sample from the phosphorus-treated land was more than 0.10% higher, in 5 more than 0.10% the lower, and in the remaining 10 the difference was less than 0.10%. For the 61 comparisons there was an average increase of 0.16% N, or 1.00% crude protein. The two samples from each field were collected at the same time, but it is pointed out that for such a comparison they should be collected at the same stage of development. If they had been taken at the same stage of bloom instead of within the same hour, it is probable that the average increase in N would have been found much greater. The difficulty of securing from a plot or field of alfalfa replicate samples closely concordant in nitrogen content is illustrated. It is concluded that in farm practice phosphorus-fertilizers applied on markedly phosphorus-deficient soils will usually cause an appreciable increase in the protein content of alfalfa hay.
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