|Estimating Nitrogen Fertilizer
Requirements in a Nitrogen
Deficient Rice Crop-95
Project Leader and Principal UC Investigators
James E. Hill - Extension Agronomist, Dept. of Agronomy & Range Science, UC Davis
Richard E. Plant - Professor, Department of Agronomy & Range Science, UC Davis
Stuart Pettygrove - Extension Soils Specialist, Dept. of Agronomy & Range Science, UC Davis
Joselito G. Real - Research Assistant, Dept. of Agronomy & Range Science, UC Davis
Julie Young - Staff Research Assistant, Dept. of Agronomy & Range Science, UC Davis
Timothy Kesselring - Research Assistant, Dept. of Agronomy & Range Science, UC Davis
John F. Williams - UC Cooperative Extension Farm Advisor, Sutter/Yuba Counties
Steven C. Scardaci - UC Cooperative Extension Farm Advisor, Colusa/Glenn/Yolo Counties
|The main objective of this project was to develop accurate
methods of estimating the amount of topdress nitrogen needed to optimize grain yield at
various growth stages with varying degrees of nitrogen deficiency.
Field experiments were established with cooperators in Colusa and Sutter counties at different preplant nitrogen rates on M-202. The crop was topdressed with ammonium sulfate at three different stages of rice development - mid-tillering, panicle initiation and 50 percent heading. Four topdressing rates of nitrogen were used.
A topdress application at panicle initiation produced the highest yields, followed by mid-tillering applications. Topdressing at 50 percent heading did not improve yields except in severely deficient plots. The yield response to topdress application is best described by a 'saturation curve. A higher rate of topdress nitrogen did not result in significant changes in grain yield for crops with excessive preplant basal nitrogen. Furthermore, lodging and moisture content at harvest increased significantly in rice that was already saturated with excessive preplant nitrogen.
Project investigators are continuing to collect and analyze yield component and leaf tissue N data. This data, as well as yield and lodging data, will be used to determine the most efficient amount of topdressed nitrogen to use in conjunction with various preplant nitrogen rates. Information from this study will also be incorporated into the rice management program CALEX/Rice.