The duration of the favorable influence of alfalfa on the cotton fields of Armenia
1934
Mirimanian, K.P.
Thus it is to be seen that during 4 years of uninterrupted cultivation to cotton following prolonged cropping to alfalfa, this soil undergoes many changes. The first year of cotton cultivation, i.e., immediately after the plowing under of the alfalfa, the humus, total nitrogen, and exchangeable Ca increased noticeably, accompanied by a slight increase of moisture-holding capacity and total porosity. From this point on, however, these values decrease slowly with a rather sharp decline by 1932. The data show that the favorable conditions created in the soil by prolonged cultivation to alfalfa were conserved during the first 3 years of cultivation to cotton, but that beginning with the fourth year of continuous cotton they began to disappear. Comparing the changes in porosity, the exchangeable Ca, and the humus content during the 4 years with the yield data for the cotton, the results presented in Table 6 were obtained. Thus, it will be seen that the yield of cotton is in perfect correlation with the changes in the soil. The 6% increase in yield in 1930 is explained partly by a surplus of nitrogen from the decomposition of the alfalfa. It may be concluded, therefore, that under conditions prevailing in the Echmiadzin district of Armenia, the favorable influence of alfalfa lasts for 3 years, but begins to decline from that point on. An effort is now being made to determine the length of time the soils of this region should be kept in alfalfa to render them suitable for cotton production.
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