**5. Future research direction**

Continuous practices of conservation agricultural (CA) has created a new generation of soil and agronomic challenges that can be strategically managed using one-off deep tillage (ST) and then returning to CA in a no-till cropping. ST is likely to offer a sustainable solution to the soil and agronomic constraints that arise from long-term CA. However, the longevity of the ST in an NT system after fixing single or multiple soil constraints needed to be explored further.

Soil re-engineering is a new approach that signifies the importance of ST, however, identifying the right soil re-engineering approaches for treating multiple interacting soil constraints needs further research before being ready for adoption at farmer scale.

Developing the next generation soil amelioration machinery for optimum amelioration outcome is required. The deep tillage technique requires heavy machinery which would involve an elevated cost to the farmers for agricultural activities. Therefore, new machinery options must be explored to attain a cheaper investment cost for agricultural activities.

Soil water holding capacity (also known as crop upper limit) is usually determined by soil textural classes and by soil organic matter. Under conservation agriculture, soil texture cannot be readily changed, therefore, soil water holding capacity remains unchanged. Using strategic tillage implements such as deep-ripper or delver in soil amelioration can bring deep subsoil clay (especially in duplex soil) to the upper sandy layers (where most crop roots grow) and improve the soil water holding capacity. In re-engineered soil, a prescribed amount of clay can be added to the sandy layer, significantly increasing water holding capacity while maintaining adequate water infiltration. Plant available water (the amount of water a soil can hold after free drainage minus the amount of water at the crop's lower limit) in ameliorated soil will differ from the constrained soil due to restricted root growth. Therefore, an improved understanding of the relationship between plant available water, plant growth and crop yield responses for strategically tilled soil is necessary.

*Strategic Tillage for Sustaining the Productivity of Broadacre Cropping in the Arid… DOI: http://dx.doi.org/10.5772/intechopen.112875*
