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Accueil du site → Doctorat → États-Unis → 1997 → Improvement of soil test phosphorus calibration and fertilizer phosphorus management in crop rotations in Moroccan dryland agriculture

Colorado State University (1997)

Improvement of soil test phosphorus calibration and fertilizer phosphorus management in crop rotations in Moroccan dryland agriculture

Amrani, Mohamed

Titre : Improvement of soil test phosphorus calibration and fertilizer phosphorus management in crop rotations in Moroccan dryland agriculture

Auteur : Amrani, Mohamed

Université de soutenance : Colorado State University

Grade : Doctor of Philosophy (PhD) 1997

Résumé
Although the main limitation of crop production in the arid and semiarid regions of Morocco is lack of sufficient rainfall, phosphorus (P) nutrient deficiencies also are major obstacle to maximum crop production. Fertilizer management is an important step in sustainability of crop production where both economic and environmental concerns are important. The objectives of this study were (i) to improve fertilizer P recommendations by the inclusion of P sorption capacities of individual soils in the P requirement model and (ii) to determine the effect of direct, cumulative, and residual P on wheat ( Triticum aestivum ) and chickpea (Cicer arietinum L.) yields under field conditions in two cropping systems : continuous wheat and chickpea-wheat. Phosphorus buffering indices were determined from sorption isotherms developed using 19 soils from the Abda, Chaouia, and Ben Sliman zones of Morocco. The greenhouse study consisted of growing wheat (cv. Merchouch) on 13 soils with four P rates (0, 3.4, 6.7, and 13.4 mg P kg-1 ). Maximum buffering capacity (MBC) of soils was incorporated into the Mitscherlich model to determine P fertilizer requirement. Soils showed a contrasting ability to adsorb P. Maximum P adsorption (Xm) varied from 146 to 808 mg P kg-1 soil. The tentative calculations of P requirement, assuming the soil test P levels in all 13 soils was 3 mg P kg-1 , showed that the amount of fertilizer needed for 90% of maximum yields varied from 1 to 15 mg P kg-1 soil. However, the fertilizer P recommendation by the usual method was 12 mg P kg -1 for all soils with a soil test P of 3 mg kg-1 . These results suggest that the inclusion of buffer indices in determining P requirement can increase the accuracy of P recommendations. In a greenhouse study, two other crops were grown after wheat. Corn ( Zea mays L., cv Kamla) was harvested after 60 days and wheat was grown to maturity. The treatments were four P rates applications (0, 3.4, 6.7, and 13.4 mg P kg-1 ) using 13 soils on the first and third crop (wheat). This greenhouse study showed that a significant response of corn to residual P occurred in soils with initial NaHCO3 -P test levels less than 6 mg P kg-1 . The response was inconsistent between 6 and 10 mg P kg-1 , and no response occurred above a soil test P level of 10 mg P kg-1 . In general, soils with more than 14 mg kg-1 NaHCO3 -P level provided adequate P for maximum yield for three succeeding crops under greenhouse conditions. Field experiments were conducted in 1994-96 at three locations : Khmis Zemamra, Sidi El Aydi, and Khmis Sidi Rhhal. Phosphorus was applied at 0, 8.9, 17.8, and 26.7 kg P/ha on both wheat and chickpea the first year. The second year, plots were split into with and without P fertilizer treatments

Mots clés : Agronomy, Fertilizer, Moroccan, Soil sciences, Phosphorus, Dryland agriculture Calibration, Soil test, Biological sciences, Crop rotations

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Page publiée le 17 février 2015, mise à jour le 18 novembre 2018