Sustainability of soil fertility status after two crop cycles of 3-years crop rotation in calcareous soils in Egypt

Includes references.

A long-term field trial was conducted under surface irrigation system at west Nile Delta RegIon (Nubaria Res. station) which represent a large area of sandy and sandy loam calcareous soils with calcium carbonate ranging between 20 to 40%, during 1996/97 until 200112002 under different resource managements i.e. 4 levels of balanced N P and K (zero, low, medium, and high), with and without organic manure application, water quantity(fanner and recommended irrigation water levels) and two crop rotation:; (prevailing and proposed). Soil samples were taken at starting of the experiment (zero-time) and after the first and second cycle of the 3~years crop rotation to follow up the concentration of available macro·and micronutrients and organic matter content. The obtained results indicated that: 1. The available residual of1\, P and K were significantly increased by increasing the applied N. P and K levels after the first and second cycles, while those of Fe, Mn and Zn were not significantly affected. 2. Application of organic manure als.;) improved soil content ofN, P, K, O.M, Fe, Zn and Mn after the second cycle of 3years crop rotation. On the average, application of organic manure increased~, P, K, O.M, Fe, Zn and Mn contents by about 16.5%,43.5%, 16.5%,51%, 18%,26% and 16.5% respectively over zero organic manure application. 3. The proposed crop rotation showed significant increase in N residual only over the prevailing one, but P and K residuals were not affected after the tirst cycle, while after the second cycle. P and K residuals were significantly increased under the proposed crop rotation, but O.M% and N~residual were eiigibly improved. 4. Fe and Mn residuals showed 10w~T values in the second cycle compared to the tirst one, may be due to the amounts removed by crops during the two cycles of 3~years of crop rotation. 5. The available soil content of N, P and K were improved under the application of the recommended water regime compared to the farmer level after the first and the second cycle. 6. The added organic manure showed the greatest relative contribution RCO/O on organic matter by 85.92%; macro-and micronutrient for N, P and K residuals by 23.1 %, 75.0% and 56.7% respectively, while it recorded 39.1 %, 25.5% and 6.0% for Zn, Mn and Fe respectively. Application of N, P and K fel1ilizers showed RC% only for the corresponding nutrient by 66.8%, 18.6% and 32.9% for N, P and K respectively. Meanwhile, water quantity showed RCO/O of 2.03% for P and 6.18% for organic matter content, while crop rotation showed RC% of 3.34~/o tor Nand 8.46% for Mn.

Summary in Arabic.

1