Effect of Chemical and Organic Fertilizers on Crop Rotation: A Fresh Look at an Unpublished Research

The effect of four different two-year rotations (cereals, fallow, clover, and sugar beet, in rotation with cereals) and four different plant nutrition managements (no fertilizer, chemical fertilizers, organic manure and combination of the latter two) was tested during 1958-61, at Karaj Research Center, Iran. Results indicated that although fallow and clover resulted in higher production of barley, as the following crop, further study would be required to check the economic value of these treatments. Such a research has to consider the ease in the availability of chemical fertilizers. The highest yield was obtained from the application of chemical fertilizers at rates of 60, 75, and 60 kg/ha N, P2O5 and K2O, respectively, and organic fertilizer (20 tons animal manure/ha), but it has to be noted that animal manure and other organic materials are not easily available for large-scale application. Although fallow resulted in 30% increase in production of cereals in 1961, reliability of such an effect needs further investigation. The effects of the interactions between rotations and chemical fertilizers, animal manure as well as their combination were also not significant. Further research is recommended to find suitable solutions to the need of the area.