Information from 2000 Missouri Rice Research Update, February 2001.

Effects of Phosphorus and White Lime on Rice Yield

Gene Stevens, Chris Moylan, Alan Sheckell, David Dunn, Holly Wilson, and Keith Birmingham

Abstract

Drill seeded rice in Missouri is usually rotated with soybeans every other year to help control red rice. Finding the right balance of soil pH and phosphorus levels between these crops is important to produce profitable yields on both crops. An experiment was conducted on an acid, low P testing soil at the Missouri Rice Farm at Glennonville to study the effects of various soil pH levels on phosphorus (P) uptake in rice. Treatments with phosphorus fertilizer increased yield but lime reduced rice yield.

Introduction

Phosphorus availability has been linked to soil pH in non-flooded soils. A study was begun in 1999 to evaluate these factors in a soybean-rice rotation cropping system.

Materials and Methods

The target pH for soybeans is 6.0. In this test, six treatments were used. All six were applied and incorporated with tillage on April 27. The first three treatments received no P applications, and applications of lime at 0, 3, and 6 ton/acre. The 6 ton/acre lime treatment was added as an intentional effort to over lime to observe the effect of high pH on rice. The next three treatments included 30 lb/acre of P, and 0, 3, and 6 ton/acre of lime, respectively. Drew rice was drill seeded on May 8, 2000. Nitrogen fertilizer (urea) was applied to the test according to standard cultural practices.

Results

In 1999, results showed that 30 lb P/acre increases yield significantly at every lime rate. However, the highest yield and milling yield (total, head rice % of broken kernels) were found to be the treatments where no lime was included. Conversely, the lowest milling percentages and yields were found in the treatments where no P was included.

In 2000, 30 lb P/acre increased yield at every lime rate except when the 6-ton lime rate was used (Table 1). The highest yield was again found to be a treatment where no lime was included. Milling percentage was not effected by the different treatments.

Table 1. Effects of phosphorus and White lime on rice milling and yield.

Lb p205	Lime ton/ acre	Milling				Yield
		1999		2000		1999	2000
		Head	Total	Head	Total	---bu/acre---
0	0	54	66	62	72	139	150
0	3	47	63	61	71	119	148
0	6	50	65	59	72	130	154
30	0	58	69	62	72	157	170
30	3	58	71	61	71	147	163
30	6	57	68	60	72	146	144

Soil samples collected before P and lime applications were made showed that the soil pH was 4.4 and the soil contained 8 lb P/acre.

Conclusion Increases in yield and milling yield were shown with the addition of P, except when 30 lb P and 6 tons of lime were applied per acre. Zinc deficiency symptoms were not observed in rice plants on the limed plots, but rice yields were decreased. Our results over two years have been consistent, and suggest that one should not apply lime before rice if in a rotation. The lime should be applied before soybeans. With the information provided from regular soil testing, rice growers should correct soil acidity in years that soybeans are grown to avoid yield losses in rice.

This experiment funded by the Missouri Rice Research and Merchandising Council.

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