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© 2008 Plant Management Network.
Accepted for publication 21 February 2008. Published 10 June 2008.

Response of Rice Yields to Phosphorus Fertilizer Rates and Polymer Coating

David J. Dunn and Gene Stevens, Missouri Agricultural Experiment Station, Delta Research Center, University of Missouri, Portageville 63873

Corresponding author: David J. Dunn. dunnd@missouri.edu

Dunn, D. J., and Stevens, G. 2008. Response of rice yields to phosphorus fertilizer Rates and polymer coating. Online. Crop Management doi:10.1094/CM-2008-0610-01-RS.

Abstract

A polymer coating of phosphate fertilizer was evaluated for rice yield response. Three rates of phosphate fertilizer, including polymer coated and non coated, were compared to an untreated check. Net returns were calculated based on crop price and input costs. At the 25-lb-acre P₂O₅ rate the polymer coated treatments produced greater yields than equivalent non coated treatments. At higher P₂O₅ rates both polymer coated and non coated treatments produced equivalent yields. The 25-lb P₂O₅ coated TSP treatment produced the greatest returns to producers.

Introduction

Rice (Oryza sativa) is an important cereal crop in the Mississippi Alluvial Delta Region. Proper phosphorus nutrition is critical for producing maximum rice grain yields. Nelson (8) in a review paper noted that an average of 22 lb/acre of rough rice yield increase could be obtained by additions of 1 lb/acre P world wide. However yield response to P fertilization in a delayed flood production system may be uncertain due to increased availability of P during anaerobic conditions following flood establishment (3,6,10). Phosphorus promotes strong early plant growth (12) and development of a strong root system. Maximum tillering is also dependent on P with a decreased number of tillers produced when rice was cultivated in a P deficient hydroponic system (9). In terms of grain removal of P an average of 60% of the above ground P utilized by the plant can be expected to be removed with the harvested grain (8).

When P fertilizers are added to soil, a complex series of reactions follow. These reactions are dependent on soil mineralogy and pH. The end result is that not all of the P contained in fertilizers is available for plants to utilize. This phenomenon, termed P fixation, has been documented for over 150 years (13). In acid or neutral soils when phosphorus fertilizers are applied to soils a percentage of the P may be strongly absorbed on the surface of soil clay minerals (4,7). In calcareous soils, phosphorus may also strongly bond with soil calcium to form insoluble compounds (5). The percentage of P becoming unavailable may range from 25 to 90% depending on soil composition, pH, and calcium level (1).

Ploymer coatings for fertilizers have several potential uses in agriculture. Slow release fertilizers with polymer coatings are commonly applied to turf and horticultural crops to increase efficiency of nutrients (11). However, use of fertilizer polymer coatings to prevent P fixation by Ca have not been reported in the literature. We investigated a water-soluble, biodegradable dicarboxylic co-polymer of maleic acid with a very high cation exchange capacity of approximately 1800 meq 100/g polymer (Avail, Specialty Fertilizer Products, Belton, MO).  This material is specific to adsorption of divalent and trivalent cations and is minimally affected by temperature, pH or ionic strength. Typically ¼ lb of Avail is added to 100 lb of P fertilizer. The added cost of Avail is approximately $1 to $2/acre. Hereafter, phosphorus fertilizer treated with Avail will be referred to as "polymer coated."

The objective of this three-year study was to compare the response of rice yields and net returns to pre-plant applications of non-coated and polymer coated triple super phosphate (TSP) fertilizer.

Field Research

Beginning in 2004 a three-year phosphorus evaluation was conducted at the Missouri Rice Research Farm located in Dunklin Co., near Qulin, MO. A dry-seeded, delayed flood rice production system was employed. The soil type is a Crowley silt loam (fine, montmorillonitic, thermic Typic Albaqualf). This location has been in a rice/soybean rotation for over 15 years. In each year a different research area was used. These areas had similar pH (6.8), K (135 lb/acre), Ca (2000 lb/acre), organic matter (1.8%), and CEC (10.0 meq 100g) levels. They differed in P levels each year (2004, 38/acre; 2005, 8/acre; and 2006, 32/acre; all measured by Bray 1 extraction). In 2004 and 2006 a maintenance application of P₂O₅ at 25 lb/acre was recommended while in 2005 a P₂O₅ application at 85 lb/acre was recommended (2). A randomized complete block experimental design with four replications was employed each year. The plot size was 25 ft by 10 ft. All methods of water management, and weed and insect control were the standard practices for cultivating dry-seeded, delayed flood rice in Southeast Missouri.

Three pre-plant P₂O₅ rates for both non-coated and polymer coated TSP (25, 50, and 100 lb of P₂O₅ per acre) were compared to an untreated control. P treatments with polymer were blended with Avail (0.25 lb polymer per 100 lb fertilizer) These treatments were applied by hand before planting and immediately incorporated using a field cultivator. The seedbed was then prepared and the rice cultivar Clearfield 161 was seeded at the rate of 90 lb seed/acre. Pre-flood N was applied at first tiller growth stage to all plots (N at 150 lb/acre, as urea). A permanent flood was then established and maintained until physiological maturity. At maturity grain was harvested from the center 5 ft of each plot. Moisture percentage was measured from each plot and yields were adjusted to a 12.5% basis. Net return was calculated using a rice price of $4.50/bu, P cost of $0.25/lb P₂O₅ and polymer coating cost of $3.00/100 lb of fertilizer.

Statistical analyses of the data were preformed with SAS (SAS Institute Inc., Cary, NC) using General Linear Modeling procedures. Fisher’s Protected Least Significant Difference (LSD) was calculated at the 0.10 probability level for making treatment mean comparisons. Regression and correlation analysis were conducted in accordance with procedures outlined by the SAS Institute.

Rice Yields and Net Returns

Phosphorus fertilization produced significant differences in rice yields each year. Analysis of variance showed no two or three factor interactions between P rate, polymer coating, and year (Table 1). Average yields for the untreated check were 164 bu/acre in 2004, 119 bu/acre in 2005, and 120 bu/acre in 2006. Difference in yields between years reflects the varying levels of background, pre-study soil test P of the three sites (2004 = 38, 2005 = 8, and 2006 = 32 lb Bray-1 P per acre). Main factor effect of polymer coating was significant at the 0.09 level. The ANOVA for net returns followed a similar pattern (not shown). At the 25 lb P₂O₅/acre rate the polymer coated treatment produced statistical greater yields than the uncoated treatment (Table 2). With increasing P rates this yield advantage diminished. At the 100-lb/acre P₂O₅ rate, coated and non-coated TSP treatments averaged the same rice yields. When the coated and non-coated treatments were compared it was found that 25 lb of P₂O₅ per acre of polymer coated TSP and 50 lb of P₂O₅ per acre of uncoated TSP produced statistically equivalent yields. When averaged across all P rates, the polymer coated TSP had a 4 bu/acre advantage over the uncoated TSP.

Table 1. Analysis of variance for rice yields for phosphorus rate
and polymer coating in 2004, 2005, and 2006 at Qulin, MO.

 * Significance values are probabilities greater than F.

Table 2. Effect of phosphorus rate using triple super phosphate (TSP) and polymer coating on rice yield and net return averaged across years at Qulin, MO.

 * Yield values followed by the same letter were not significantly different at the P = 0.1 level.

When net returns to producers were compared the 25 lb/acre P₂O₅ rate of polymer coated TSP produced net returns which were statistically and numerically equivalent to the 100/acre P₂O₅ rate of uncoated TSP. This reflects the lower input cost of the 25 lb of P₂O₅ per acre coated TSP ($6.25 TSP + 1.50 coating) compared to the 100 lb of P₂O₅ per acre TSP ($25.00 TSP). The yield advantages obtained with the polymer coated material translated into significantly greater returns per acre for the 25 lb/acre P₂O₅ rate. When all P rates were averaged the polymer coated TSP treatments provided $14.00/acre more net return.

Summary

Based on this three-year study, rice grain yields were significantly affected by P rate. A significant interaction was not detected by ANOVA between P rate and polymer coating. However, polymer coated TSP was more effective at increasing rice yields than uncoated TSP. A 25 lb/acre P₂O₅ application of polymer coated TSP was as effective as 50 lb of P₂O₅ per acre of uncoated TSP. The 25 lb P₂O₅/acre coated TSP treatment produced the greatest returns to producers. The polymer coating increased P use efficiency and profitably increased overall yields. At the 25 and 50 lb of P₂O₅ per acre the yield advantage of the coated TSP was great enough to pay for the increased cost of the coated material. Higher yields lead to lower production costs per bushel and increase overall profitability. Rice producers should consider using coated P fertilizers on some of their rice acres.

Acknowledgment

This research was supported by a grant from Specialty Fertilizer Products, Belton, MO.

Literature Cited

1. Brandon, D. M., and Mikkelsen, D. S. 1979. Phosphorus transformations in alternatively flooded Calfifornia soils: I cause of plant phosphorus deficiency in rice rotation crops and correction methods. Soil Sci. Soc. Am. J. 43:989-994

2. Buchholz, D. D. 1987. Soil Test Interpretations and Recommendations Handbook. Coll. of Ag., Univ. of Missouri, Columbia, MO.

3. Doberman. A., Cassman, K. G., Mamaril, C. P., and Sheehy, J. E. 1998. Management of phosphorus, potassium, and sulfur in intensive, irrigated lowland rice. Field Crops Res. 56:113-138

4. Kurtz, L. T. 1953. Inorganic phosphorus in acid and neutral soils. Soil and Fertilizer Phosphorus in Crop Nutrition. W. H. Pierre and A. G. Norman, eds. Agronomy 4:59-88.

5. Mattingly, G. E. G. 1975. Liable phosphate in soils. Soil Sci. 119:369-375.

6. Mitsui, S. 1956. Inorganic nutrition fertilization and soil amelioration for lowland rice, 3rd Edn. Yokendo, LTD. Tokyo, Japan.

7. Mott, C. J. B. 1970. Sorption of anions by soil. Monogr. No 37:40-52. Soc. of Chem. and Indust., London, UK.

8. Nelson, L. E. 1980. Phosphorus nutrition of cotton, peanuts, rice, sugarcane, and tobacco. Pages 693-736 in: The Role of Phosphorus in Agriculture. Am. Soc. Agron., Madison, WI.

9. Olson, K. L. 1958. Mineral deficiency symptoms in rice. Agric. Exp. Stn. Bull. No. 605., Coop. Ext. Serv., Univ. of Arkansas, Little Rock, AR.

10. Ponnamperuma, F. N. 1965. Dynamic aspects of flooded soils and the nutrition of the rice plant. Pages 295-328 in: The Mineral Nutrition of the Rice Plant. John Hopkins, Baltimore MD.

11. Shaviv, A., and Mikkelson, R. L. 1993. Controlled-release fertilizers to increase efficiency of nutrient use and minimize environmental degradation: A review. Nutrient Cycling Agrosys. 35:1-12.

12. Terman, G. L., and Allen, S. E. 1970. Fertilizer and soil P uptake by paddy rice, as affected by soil P level, source, and date of application. J. Agric. Sci. (Cambridge). 75:547-552.

13. Wild, A. 1950. The retention of phosphate by soils, a review. J. Soil Sci. 1:221-238