Sustainable intensification and soil physical properties: A synthesis of data from contrasting cropping systems and ecologies in the Indo-Gangetic Plains

Description of the topic

Conservation agriculture (CA) influences crop growth and yield through changes in soil physical properties, which are also thought to be beneficial for longer-term soil quality and sustainability. Frequently observed changes include increased aggregate stability, water infiltration rate, water retention, decreased penetration resistance (an indicator of ease of root penetration), and reduced sub-soil compaction as well as reduced risk of soil erosion. These soil physical changes are generally associated with increased organic carbon content that can result from: (1) increased total organic matter input from crop residues compared to the conventional system; (2) altered composition or location of inputs resulting from cropping system diversification; (3) concentration of organic matter near the soil surface caused by elimination of tillage; or (4) a combination of these factors. However, the mechanisms underlying these soil physical changes are not well understood. In alarge number of experimental sites across the Indo-Gangetic Plains (IGP) of South Asia, combinations of CA-based practices have been applied over several years and on different soil types and cropping systems. The main aim of the proposed project is to synthesize existing data on soil chemical and physical properties to determine whether thresholds exist in terms of amount and quality of organic matter inputs needed to bring about beneficial changes in soil physical properties that will ultimately improve adaptation to climatic variability and extremes. A second aim is to test the suitability of a range of novel physical measurement techniques for detecting and quantifying changes in soil organic matter and physical properties.

Work expectations

The research will involve the use of a range of soil science techniques including thermo-gravimetric analysis (TGA), currently being investigated in collaboration with Rothamsted Research and China Agricultural University; TGA is a means of distinguishing between organic C in different chemical forms, thought to be significant in altering physical properties. Other techniques will include measuring soil shear strength and compression through triaxial testing. A third aim is to develop simple measurements of potential value for field use. The water release characteristics and water repellence of soils will also be measured to evaluate differences in pore sizes due to the effects of CA. These data will be used to link hydraulic and mechanical properties with simple but mechanistic models.

Required skills

Previous research experience in soil science, agronomy or soil physics.