By Bruce A Linquist
This post is somewhat a repeat of last year’s. However, while last year the rice price was low, this year we have both low rice prices and high fertilizer costs. Therefore, there is even more reason to carefully manage your fertilizer input costs. Below are some suggestions on how you can reduce your costs.
First, do not plan a top-dress nitrogen (N) application. If you routinely plan a top-dress N application, put that amount of N into your aqua application instead. We have done a lot of research on this and have seen no benefit of splitting the total N rate between a preplant aqua and top-dress N applications. If the field remains flooded early in the season, this aqua-N is efficiently used. This saves cost for two reasons. First, aqua-N is a cheaper N source than ammonium sulfate (typical top-dress N source). Second, you avoid airplane costs associated with topdressing. These savings could amount to $25+/acre. I am often asked about the benefits of the sulfur (S) found in ammonium sulfate. I have never seen S deficient rice in CA; and in the testing that I have done, the soil and plant S concentrations have always been above critical levels.
Was your field fallow last year? For the past four years we have been doing research at the Rice Experiment Station on how to manage N fertilizer in rice fields where the previous year the field was fallowed. I have written about our findings more extensively in previous articles. The bottom line is that there is more soil N available from fields which were fallowed the previous year. Thus, if you have a field coming out of fallow (and it had been in rice prior to that for several years) you can reduce N fertility rates. Our research shows that rates can be reduced by 20-40 lb N/ac.
Importantly, for both the strategies mentioned above, it is important to keep a close eye on the crop around panicle initiation (40-45 days after planting) to see if it is displaying any signs of N deficiency. This can be done with a Leaf Color Chart, a Green Seeker, or plant analysis – all of which have been discussed in previous newsletters. If the crop is showing signs of deficiency at this time, apply the top-dress of N.
Source : ucanr.edu