|Evaluation of Yield
Project Leader and Principal UC Investigators
Richard E. Plant, professor, Dept. of Agronomy and Range Science, UC Davis
G. Stuart Pettygrove, Extension soil specialist, UC Cooperative Extension, Dept. of land, Air & Water Resources, UC Davis
John F. "Jack" Williams, Farm Advisor, UC Cooperative Extension, Sutter/Yuba counties
Julie A. Young, Dept. of Agronomy and Range Science, UC Davis
|This project is evaluating
precision agriculture technology to determine whether it will work well for California
rice production and, if so, to develop practices for growers to use it effectively.
This project also examined the effect of varying fertilizer levels on within-field yield
variability. Experiments were carried out on M-202 and Koshihakari.
In order for precision agriculture to be useful for California rice production, the underlying causes of observed variability in grain yields must be determined. Researchers monitored electrical conductivity (EC) to determine differences in salinity and clay content and examined infrared photography to analyze crop vegetative canopy. Differences between aerial images and the EC map indicate variability is not caused by soil factors. Similarly, differences in yields compared to aerial photographs did not show a correlation with vegetative growth.
A statistical analysis of last years results is still in progress. However, a visual interpretation of the data from 1998 and 1999 indicates that laser leveling appears to have reduced yield variability. An elevation map of the field made in 1998 indicates that yield was lowest in the lowest areas of the field. An aerial photograph of the field taken in May 1998 indicates that rice emerged from the water latest in the low areas of the field. This may have reduced yield in those areas due to the short season that year. Visual comparison of soil mineral nutrient levels, as well as electrical conductivity, indicates that the area of highest yield corresponds to the area of highest soil phosphorous, suggesting a possible deficiency for that nutrient. This year researchers are planning to collect soil samples in high and low yielding areas.
Fields planted to specialty rice appear to be even more susceptible to soil variability. The Koshihakari field had two large low-yielding areas. These are easily visible on the aerial photograph, suggesting the cause of the low yield is a reduced vegetative stand. Leaf tissue samples collected from the field are still undergoing laboratory analysis but visual inspection of the field confirmed this. Direct sampling is planned for 2000 to further assess the cause of low yields.