Variability in soil organic carbon fractions relevance to different agricultural practices

الملخص EN

A field trail was conducted at The Experimental Farm, Fac.

of Agric., Al- Azahar Univ., Assiut, located 375 km south of Cairo, Egypt (27 12- 16.67= N latitude and 3 09- 36.86= E longitude) during the growth seasons of summer 2016 and winter 2016/2017 to assess the effect of tillage and nitrogen fertilization practices on soil organic matter partitioning into the functional compartments with different dynamics.

The study included three plowing manner (No plowing, NP, Minimum plowing, MP and Traditional plowing, TP) and two nitrogen sources (Urea 46.5% N as a fast nitrogen fertilizer and ureaform 40% N as a slow nitrogen fertilizer).

The obtained results indicated that plowing manner had the greatest effect on soil organic carbon (SOC) and its various fractions (permanganate oxidizable carbon, KMnO4-C, particulate organic matter carbon, POM-C, microbial biomass carbon, MBC, and mineralized carbon, C min) under different crop growth.

The trends observed with SOC fractions indicated that minimum plowing managements created a more favorable plant growth environment relative to traditional plowing.

MBC was found to be sensitive to nitrogen management.

The results supported the hypothesis that changes in surface SOC by tillage can be predicted by POM-C, KMnO4-C and C min.

On the average basis, POM-C was the most sensitive to tillage managements among all the SOC fractions and represented the largest portion of the total SOC (43.75%) followed by KMnO4–C (4.75%) then C min (1.66%).

The adoption of conservation tillage practices offers soil C sequestration opportunity and soil health improvement under sunflower- wheat rotation in Assiut region, Upper Egypt.

It could be concluded that minimum plowing practice protected soil organic carbon compared to the other plowing treatments.

Minimum plowing management increases soil organic matter and improves soil fertility and has potential for increasing the nutrient supply to crops through changes in the mineralization and immobilization of nutrients by microbial biomass.