Biochar addition combined with daily fertigation improves overall soil quality and enhances water-fertilizer productivity of cucumber in alkaline soils of a semi-arid region

•Overall soil quality (OSQ) was evaluated base on a wide range of soil properties.•Biochar addition (BI) improved OSQ and thereby increased crop productivity (CP).•BI could further enhance both OSQ and CP when combined with daily fertigation.•The OSQ played a pivotal role in determining CP under conditions with BI.