SUNFLOWER (Helianthus annus L.) HULL AS AN ORGANIC AMENDMENT AND ITS EFFECTS ON SOIL PROPERTIES

The incorporation of sunflower hulls can improve the physical and chemical properties of the soil. Therefore, a study was conducted in order to evaluate the incorporation of O (A0); 55 (A1) and 88 (A2) Mg ha(-1) of sunflower hulls in the arable layer of a Typical Haplustoll. Fifty-two months after hulls were incorporated into the soil, a strong increase of organic carbon (CO) was observed in A1 (15.5 g kg(-1)) and A2 (16.6 g kg(-1)), as compared with AO (11.6 g kg(-1)). Soil pH levels were 7.5 in A0 and 7.3 in A1 and A2. After the 52 month-period, P levels remained high in A1 (21 mg kg(-1)) and A2 (27 mg kg(-1)), as compared with AO (18 mg kg(-1)). The highest soil aggregate stability was observed in A1 and A2 treatments after 40 and 52 months. At the end of the experiment, soil water retention at 0.01 MPa was 30% higher than the control treatment, while values observed at 0.033 MPa were 23% higher than A0. However, no significant differences between treatments were observed at 1.5 MPa. The available water capacity of A1 and A2 showed significant differences compared to A0. Based on these results, it can be concluded that the application of this residue can be recommended.