Impact of organic residues and mineral fertilizer application on soil–crop system: II soil attributes

The effects of crop residues alone (Cr þ ) or combined with inorganic fertilizer (FCr þ ) sewage sludge (SS) and humentos (H) on soil properties were studied in a five-season wheat–guar rotation. Incorporation of Cr þ and SS significantly decreased pH by 5–9%. Highest organic carbon (OC) was observed in SS plots, whereas Cr þ resulted in values threefold that of the control. The added effect of Cr þ (46%) combined with fertilizer on total nitrogen (TN) was greater than Cr þ by 28%. The fraction of total residue N mineralized was 71%, whereas net N mineralized in Cr þ , SS, H and FCr þ plots at 0–20 and 20–40 cm depths were 39.8, 52.3, 11.4, 66.7 mg kg 71 and 21.2, 27.9, 8.2, 41.2 mg kg 71 , respectively. Integrated application of Cr þ with fertilizer had a synergistic effect on P content (3.49–3.69 units), but soil levels has never exceeded 13 mg P kg 71 . Sole Cr þ significantly increased topsoil cation-exchange capacity (CEC) compared with the control treatment (9.39–21.59%). Application of SS, FCr þ and Cr þ significantly increased water-holding capacity and decreased bulk density by 9–15% and 8–9%, respectively, suggesting that such practice can restore the productivity of degraded soils and improve crop yields.