Among CSSHP fields, we have only a few which have changed from an annual to a perennial cropping system, or from a perennial to an annual cropping system during the project. The few examples we have suggest that changing from an annual to a perennial system improves soil health, while changing from a perennial to an annual system depresses soil health.
Based on our analysis of PLFA scores over 7 years, we conclude:
We use the PLFA (Phospho-lipid Fatty Acid) test to measure microbial life in CSSHP fields. Only when comparing dryland VS irrigated fields, annual VS perennial fields and fields with various levels of tillage intensity, did we see significant differences in microbial life among these groups. Grazed VS ungrazed fields, fields with organic matter amendments VS fields with none, and fields with different soil types did not show significant differences in microbial life measurements.
Comparing dryland VS irrigated and perennial VS annual systems, PLFA results clearly show that irrigated and perennial fields have more microbial life than dryland and annual fields. Irrigated perennial fields had the highest average scores and dryland annual fields had the lowest. This bar graph also suggests that perennial systems with their lack of soil disturbance are more beneficial for microbial life than supplemental irrigation water alone.