Maize Water Use in Living Mulch Systems with Stover Removal

Constraints to maize (Zea mays L.) stover biomass harvest may be mitigated by using a living mulch (LM) to offset C exports and control soil erosion. Living mulches can compete with the main crop for resources, particularly water. The objectives of this research were to quantify soil water dynamics and maize water use in continuous maize with stover removal. Continuous soil water content (SWC) and reproductive whole-plant water use were measured in no-till maize growing in LMs of creeping red fescue (CF) (Festuca rubra L.), Kentucky bluegrass (KB) (Poa pratensis L.), and a no-LM control between 2008 and 2010 near Ames, IA. In 2 yr with excessive rainfall (2008 and 2010), LMs increased SWC compared to the control at 15 cm. No-till LM treatments lowered grain yield in 2008 and 2010 compared to the control, although a KB fall strip-till treatment, which was part of the larger research study, produced yields that were not different than the control all 3 yr. Reproductive water use efficiency for no-till KB in 2008 and 2009 (51 and 42 g grain per cm water) was 21 and 14% greater than the control (42 and 37) but 24% lower in 2010 (41 vs. 51). Maize water use in the control exhibited a bimodal response averaged across the 3 yr with peak water use occurring at the R1 through R2 period (0.58 cm d(-1)) and declining to 0.26 cm d(-1) during R5 through R6. In contrast, no-till KB exhibited a simple negative linear relationship with water use rates declining from a high of 0.47 cm d(-1) during the R1 through R2 period to 0.22 cm d(-1) during R5 through R6. These results indicate LMs may increase SWC and utilize water more effectively, particularly when combining strip-till and herbicide management.