This continuing project is evaluating the impact of grower management practices on nutrient cycling.  The goal is to develop improved fertility management guidelines for rice growers.

Fertility management

The first objective of this study is to identify needed changes in fertility management following legislated reductions in rice straw burning.   In 2004 nitrogen rate fertility trials were expanded to include 26 growers and 71 field sites throughout the Sacramento Valley. Three different nitrogen rates were applied on a variety of soils under different management practices.  Extensive soil and plant sampling and monitoring followed.

In contrast to 2003, where yield reductions were observed in fields in which straw treatments alternated from year to year, 2004 yields were lower across the reduced nitrogen treatments for all straw management practices. The result was likely due to differences in weather patterns and improved growing conditions in 2004, when overall yields increased significantly.  Nitrogen concentrations in tissue samples were below the current critical limits for a majority of fields sampled at mid-tillering and panicle initiation across all nitrogen rates. However, increased nitrogen rates did not significantly improve rice yields, suggesting that current mid-season tissue nitrogen guidelines need revision.

Liming study concludes

Last year saw the completion of a study on the impact of liming on rice production at two Sacramento Valley locations — Princeton and Richvale.  Calcium is an essential nutrient involved in the processes of cell elongation and division.  Nearly one fifth of previously surveyed growers reported using either lime or gypsum to increase calcium availability despite the lack of supporting scientific evidence.

Results from this study indicate that liming has no appreciable effect on straw or grain yields, head rice production or mid-season plant growth parameters under standard fertilizer and herbicide applications.

While most weeds were unaffected by liming, there was a significant reduction in ricefield bulrush following liming.  Laboratory tests suggest that the reduction is the result of decreased bulrush germination, and not improvements in the competitiveness of rice. 

In addition, liming increases soil nitrogen availability from 10 to 20 pounds/acre in the year following application and increases the amount of force required for primary tillage by up to 25 percent.  Given the lack of any observed economic benefit, lime application does not appear to be cost effective.