Abstracts

Presented by Luke Matthews - Email: lmatthews@calrice.org

Rice and corn comprise 70% of the winter food supplies for waterfowl in the Central Valley. However, agricultural practices such as post-harvest treatments of rice and corn fields have been changing in the Central Valley. These changes are largely due to recurring drought conditions and shifting agricultural economics. Currently we lack data regarding how post-harvest treatments in rice and corn fields affects waste grain availability, yet these data are essential to determine the carrying capacity of agricultural lands for waterfowl during winter in the Central Valley. To address this knowledge gap, we estimated the abundance of available waste grain (lbs/ac.) using dry field transects and dry field soil cores, and flooded field (wet) soil cores in 84 rice fields and 47 corn fields in 2016 and 2017. Our results indicate that the available waste grain in rice fields varied significantly among post-harvest treatments. Fields that received no post-harvest treatment (stubble left standing; no incorporation of straw) had the greatest amounts of waste rice, whereas fields that were disced, disced and rolled, or burned provided the least amount of available waste rice. The mean abundance of waste rice grain in dry fields, across all treatments, was 286 lbs/acre. Estimates of waste rice in flooded fields averaged only 132 lbs/acre, significantly lower than in the same fields prior to flooding. Variation in available waste grain in corn fields was greater than rice fields. The abundance of available waste corn in fields that were not incorporated post-harvest averaged 228 lbs/acre, whereas fields that were incorporated contained only 52 lbs/acre. The average available waste corn, across all post-harvest treatments, was 164 lbs/acre. Our results clearly show that the availability of waste grain in rice and corn fields is affected by post-harvest practices. If these practices change, estimates of carrying capacity for wintering waterfowl will be impacted.