Document Type : Research Paper
Authors
1
Associate Professor, Agricultural and Natural Resources Research Center of Khorasan Razavi
2
Instructor, Soil and Water Research Department of Agricultural and Natural Resources Research Center of Khorasan Razavi
Abstract
In order to study variations of organic carbon, nitrogen, phosphorous, potassium, iron, zinc, copper, and manganese available in soil in response to different wheat based rotations, an experiment was conducted for 5 years with completely randomized block design, with 8 treatments and 3 replications. Treatments were: T1- continuous wheat culture, T2- wheat, wheat, wheat, canola, wheat, T3- wheat, sugar beet, wheat, sugar beet, wheat,T4- wheat, potato, wheat, potato, wheat, T5- wheat, potato, wheat, canola, wheat, T6- wheat, sugar beet, wheat, potato, wheat, T7- wheat, corn, wheat , potato, wheat, T8- wheat, corn, wheat, sugar beet, wheat. Results showed that the amount of macronutrients in surface soil layer varied with rotation and number of years. The %OC and the residual macronutrients and micronutrients were affected significantly in 5 years: %OC was reduced, the residual N increased, the residual P remained constant, and the residual K decreased in 5 years. Also, the residual Fe and Zn increased while the amount of residual Mn decreased, but the residual Cu remained unchanged in 5 years. The amount of %OC and the residual macronutrients and micronutrients were affected significantly by different rotations. T1 rotation had the highest levels of %OC and the amount of residual N, Fe, and Zn and the lowest level of residual K. T2 rotation, too, had the highest %OC and residual N, but the lowest level of residual P, Zn , and Fe and the highest level of residual Mn and Cu. T3 rotation had the highest level of residual P. T4 rotation resulted in the lowest level of %OC and residual N. T5 rotation had the highest level of %OC and the residual N and K. T7 rotation resulted in the lowest level of %OC and residual N. T8 rotation had the highest level of residual P.
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