Nitrogen Efficiency is Increased through Banded Fluid Fertilizer in Rice Production

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Fred T. Turner, Professor, Michael F. Jund, Research Associate, and Lee Tarpley, Assistant Professor, Texas A&M University Research and Extension Center, 1509 Aggie Drive, Beaumont, TX 77713

Abstract

A combination of fluid fertilizer and early floodwater establishment could reduce fertilizer and application inputs or increase rice yields by maximizing N efficiency. A fluid fertilizer applicator was attached to a rice drill so 100 or 70% of the 150 lb of N fertilizer per acre was applied as fluid fertilizer while drill-seeding rice. The N uptake and rice yields of subsurface, banded fluid fertilizer treatments were compared with those of broadcast dry granular urea applied in 1, 2, or 3 applications. Floodwater irrigations were established at the 4- or 6-leaf developmental stage. The field plot research was conducted on clay soil in 2003 and clay and silt loam in 2004. Fluid fertilizer applied during planting, relative to broadcast dry granular urea, increased N uptake under both flooding regimes in 2003 and from both soil types in 2004, and also increased yield from both soil types in 2004, and conventional flood timing in 2003. Rice grain yields were as great as from split applications, suggesting the single application of subsurface banded fertilizer at planting can help reduce or eliminate subsequent N applications.

Introduction

Rice production practices across most of the southern U.S. consist of drill-seeding rice in dry soil and establishing a flood 25 to 30 days later. Nitrogen fertilizer applications vary in rate and timing with the number of applications generally ranging from two to five, depending on individual producer management. In drill-seeded rice, maximum grain yield has been obtained with split topdress applications of N timed to match the N demands of the crop (9,11). Therefore, producers sometimes use multiple aerial applications of N to improve N efficiency and yield compared to one application (1,10). However, current aerial application cost of ~ $8/acre for applications of urea at less than 110 lb/acre can be higher than the cost of N fertilizer on a per-pound basis.

Traditionally, dry granular urea has been broadcast on the soil surface and incorporated when applied pre-plant or washed into the dry soil by irrigation water when applied pre-flood. Broadcasting N on the soil surface along with wetting and drying cycles that encourage nitrification and denitrification have reduced N use efficiency in rice (7). In addition, in wet years, producers may be faced with broadcasting urea onto a wet soil, which further reduces N efficiency when subsequent flood irrigation can not effectively wash the applied N deep enough into the soil to avoid the oxidized layer at the soil surface. Any N in the surface-oxidized layer is subject to denitrification upon flooding (4).

Subsurface banding of N fertilizers has shown improved N efficiency in other crops compared to broadcast applications. Winter wheat yields were improved 15 to 32% when N was subsurface banded compared to surface broadcast under no-till management (6). In California rice production, aqueous ammonia has been knifed into the soil as a pre-plant N source for water seeded rice (9). The use of urea supergranules and mudballs containing urea placed by hand about 4 inches deep into flooded rice soils have increased N use efficiency in transplanted rice (5). The increase in N efficiency when the N source is concentrated in a small area of the soil has been attributed to the delay in nitrification due to the high salt content in the vicinity of the fertilizer band (2). In flooded rice, the delay in nitrification and resulting increase in fertilizer N availability should be extended when soil near the fertilizer band becomes anaerobic due to flooding. Subsurface banding of 70 to 100% of all N as fluid fertilizer at planting, coupled with earlier flood establishment, has potential to reduce rice production costs by reducing N application costs and lowering N rates through improved uptake. Additional benefits of earlier flood establishment are reduced herbicide applications, reduced irrigation flushes and earlier crop maturity. Therefore, our objective was to compare subsurface banded fluid fertilizer with broadcast dry granular urea when flood irrigating at the 4- or 6-leaf stage.

Field Experiments Using Two Water Management Systems

Subsurface banded fluid fertilizer was compared to dry granular urea in field plots on a League clay soil (Oxyaquic Dystruderf) at the Texas A&M University Research and Extension Center near Beaumont, TX in 2003. During 2004, the evaluation was expanded to include Nada silt loam soil (Albaquic Hapludalf) about 150 miles west of Beaumont at the David R. Wintermann Rice Research Station near Eagle Lake, TX. Plot size was 5.33 ft wide by 20 ft long for clay and 5.33 ft wide by 16 ft long for silt loam soil. Fertilizer treatments were evaluated using either "early" (flood at 3- to 4-leaf growth stage) or "delayed" (flood at 6- to 7-leaf growth stage) flood water management systems. Each treatment was replicated four to eight times. Fluid fertilizer was applied in bands approximately 2 to 3 inches below the soil surface during planting. Four fluid fertilizer applicator knives (Figs. 1 and 2) were spaced 16 inches apart to provide a band of fluid fertilizer between every other drill row spaced 8 inches apart. The fluid fertilizer was a urea-based ammonium polyphosphate mixed with KCl. Dry urea treatments were broadcast by hand onto the soil surface just prior to planting. Supplemental P and K were applied to dry urea treatments so that both fluid and dry treatments received (P₂O₅ at 30 lb/acre) and (K₂O at 20 lb/acre). The rice (Oryza sativa L.) cultivar ‘Cocodrie’ (LA cross Cypress/L202/Tebonnet, PI606331) was drill-seeded between April 1 and 20. Plots were flooded at the 4- or 6-leaf plant developmental stage and remained flooded until about 10 days prior to harvest. Plots not flooded until the 6-leaf stage were flush irrigated as needed. The three N treatments were 150 lb/acre applied: (i) at planting; (ii) 70% at planting and 30% at mid-season; and (iii) 17 to 30% at planting, 40 to 50% at preflood, and 30 to 33% at mid-season. The non-experimental cultural practices were those typical for Texas rice as described by the 2004 and earlier editions of the Texas Rice Production Guidelines (8). Above-ground biomass samples were taken from the 4 center rows at mid-season in 2003 and at late boot in 2004. Samples were dried, weighed, ground, and sent to laboratories for analyses (Total N, P, and K by Olsen’s Agricultural Lab, McCook, NE in 2003 and by Waters Agricultural Lab, Camilla, GA in 2004). At maturity, rice was harvested using a plot combine. Grain samples were dried to 12% moisture, weighed, and yields calculated. Statistical analyses were conducted using SAS (SAS Institute Inc., Cary, NC), and mean separations were performed using the least significant difference procedure.The statistical analyses were also performed by comparing confidence intervals around the sample medians (3) but the conclusions were the same. Differences due to the timing of flood were performed as paired comparisons within the nitrogen treatments.


Fig. 1. Backswept applicator knife applying fluid fertilizer about 3 inches below the soil surface at planting.		Fig. 2. Applying fluid fertilizer while planting using fluid applicator attached to grain drill.

Nitrogen Uptake

2003. Nitrogen and floodwater treatments were evaluated only on clay soil in 2003. Since rice plants were sampled just prior to applying mid-season N in 2003, N uptake could only be determined in treatments receiving all N pre-plant. Early flood establishment increased N uptake in 2003 when N at 150 lb/acre was applied at planting, regardless if N was applied dry or in fluid (Table 1). In addition, the fluid fertilizer treatment increased mid-season N uptake over that of broadcast dry granular urea in 2003 (Table 1).

Table 1. The N uptake by rice plants at mid-season in 2003 on clay soil flooded at 4- or 6-leaf rice developmental stage near Beaumont, TX. The N uptake at booting stage in 2004 averaged for 4- and 6-leaf floodwater management on clay and silt loam soil, near Beaumont and Eagle Lake, TX, respectively.

N treatment of 150 lb/acre	2003 N uptake at mid-season (lb/acre)		2004 N uptake avg. at booting (lb/acre)
N treatment of 150 lb/acre	4-leaf on clay	6-leaf on clay	4- and 6-leaf on clay	4- and 6-leaf on silt loam
Fluid, all during planting	103 a	93 a	152 a	142 a
Dry, all just prior to planting	82 b	66 b	104 b	126 b
2-way split (70% planting + 30% at mid-season)	--	--	105 b	113 b
3-way split (all dry, 17% at planting + 50% at flood + 33% at mid-season)	--	--	105 b	143 a
No fertilizer	10	--	24	45

Within columns, means followed by the same letter are not significantly different. (P ~ 0.035 to 0.067 based on a median test adjusted for multiple comparisons, or P ~ 0.05 based on a mean test). The treatment without fertilizer addition was excluded from the comparison.

2004. Nitrogen and floodwater treatments were evaluated on both clay and silt loam soils in 2004. The N uptake was not influenced by the 4- or 6-leaf flood establishment in 2004, possibly because of early-season rain on clay soil and high native-N supply on the silt loam soil. Therefore, the 2004 N uptake data in Table 1 are the average N uptake for the 4- and 6-leaf flood treatment on each soil. On the clay soil, N uptake for the fluid fertilizer treatment was 152 lb/acre, higher than the three other N treatments, which averaged about 105 lb of N uptake per acre. On the silt loam soil, N uptake for the fluid fertilizer treatment was 142 lb of N per acre, which was equivalent to that of the 3-way split of dry fertilizer, and higher than the dry fertilizer applied at planting and the 2-way N split.

Based on the 2003 results, the early flood has the potential to increase N uptake. In addition, across the two years the fluid fertilizer delivery almost always led to greater N uptake relative to the applications with dry granular urea.

Nitrogen Treatment Effects on Rice Yield Under 4- and 6-Leaf Flood

Results from 2003 (Table 2) show that the non-fertilized rice plants yielded 2100 and 1500 lb/acre when flooded at the 4- and 6-leaf stage, respectively, and suggest that 4-leaf flood created conditions for maximum yield and/or increased soil N uptake. The fertilized rice plants also yielded more when flooded at the 4-leaf rather than the 6-leaf stage, possibly because delaying the flood until the 6-leaf stage encouraged more denitrification. The N treatment effect on rice yield was most evident under the 6-leaf flood, which produced rice yields in the range of 5200 to 6220 lb/acre (Table 2). The fluid fertilizer treatment applied during planting led to greater yield than the other treatments. The N source effect on rice yield in 2003 under the 4-leaf flood was less pronounced and ranged from 6200 to 6939 lb/acre. The yield (6939 lb/acre) of the fluid fertilizer treatment applied during planting and that of the “all dry fertilizer at planting” (6869 lb/acre) were greater than the 3-way and 2-way split applications (Table 2).

Table 2. Fertilizer treatment effects for 2003 rice yields on clay soil flooded at 4- and 6-leaf stages and for 2004 yields on clay and silt loam soils when 150 lb of N per acre was applied all at planting or as 2- and 3-way splits.

N treatment of 150 lb/acre	2003 yield (lb/acre)		2004 yield (lb/acre)
N treatment of 150 lb/acre	4-leaf	6-leaf	Clay	Silt loam
Fluid, all during planting	6939 a	6220 a	6430 a	8440 a
Dry, all at planting	6869 a	5220 c	5930 c	7560 b
2-way split (FF + dry)	6200 c	5200 c	6450 a	8330 a
3-way split (all dry 17% at planting + 50% at flood + 33% at mid-season)	6400 b	5800 b	6150 b	8110 a
No fertilizer	2103	1540	2086	5167

In 2004, floodwater management did not significantly influence yield of N fertilized rice plants, so rice yields in Table 2 are the average of the 4-and 6-leaf flood yields on each soil type. Within columns, means followed by the same letter are not significantly different. (P ~ 0.035 to 0.067 based on a median test adjusted for multiple comparisons, or P ~ 0.05 based on a mean test). The treatment without fertilizer addition was excluded from the comparison.

In 2004, floodwater management did not influence the yield of N-fertilized rice plants, so rice yields in Table 2 are the average of the 4-and 6-leaf flood yields on each soil type. On clay soil, the yields from the fluid fertilizer applied during planting treatment and the 2-way split were greater than those from the dry fertilizer at planting treatment and the 3-way split. On silt loam soil, rice yields were higher, but the N treatment effects were similar to those on clay soil. The higher rice yields on silt loam soil were probably due to better climatic conditions, and that the silt loam produced higher rice yield without N fertilizer (i.e., 2086 and 5167 lb/acre for the clay and silt loam soil, respectively).

Summary

As fuel and fertilizer costs continue to increase, rice producers look for ways to improve N efficiency. Results from this study indicate that banded fluid fertilizer applied at planting can improve N efficiency as demonstrated through increased N uptake compared to traditional broadcast applications. The N uptake for fluid fertilizer applied in a single application at planting was greater than the 2- or 3-way split, especially on clay soil. Rice grain yield was as great or greater than that obtained from the split applications suggesting that a single application of subsurface banded fertilizer at planting can contribute to the reduction or elimination of subsequent N applications. In addition, by utilizing the flooded rice culture through early flood irrigation, the efficiency of subsurface banded fluid fertilizer is further enhanced.

Acknowledgments

The authors are grateful for the support and funding provided by the National Fluid Fertilizer Foundation and for the labs providing plant analyses. In 2003, Olsen’s Agricultural Lab in McCook, NE contributed and in 2004, the Waters Agricultural Lab in Camilla, GA contributed. Also, without the equipment and expertise supplied by Texas Liquid Fertilizer, this study could not have been conducted.

Literature Cited

1. Fageria, N. K., Slaton, N. A., and Baligar, V. C. 2003. Nutrient management for improving lowland rice productivity and sustainability. Adv. Agron. 80:63-152.

2. Hendrickson, L. L., Keeney, D. R., Walsh, L. M., and Liegel, E. A. 1978. Evaluation of nitrapyrin as a means of improving N efficiency in irrigated sands. Agron. J. 70:699-703.

3. Iman, R. L., and Conover, W. J. 1983. A Modern Approach to Statistics. John Wiley and Sons, NY.

4. Patrick, W. H., Jr. and Reddy, C. N. 1977. Chemical changes in rice soils. In: Soils and Rice. Pages 361-379 in: Int’l Rice Res. Inst., Los Banos, Laguna, Philippines.

5. Prasad, R., and De Datta, S. K. 1979. Increasing fertilizer nitrogen efficiency in wetland rice. Pages 465-84 in: Nitrogen and Rice. Int’l Rice Res. Inst., Los Banos, Laguna, Philippines.

6. Rao, S. C., and Dao, T. H. 1996. Nitrogen placement and tillage effects on dry matter and nitrogen accumulation and redistribution in winter wheat. Agron. J. 88:365-371.

7. Reddy, K. R., and Patrick, Jr., W. H. 1975. Effect of alternate aerobic and anaerobic conditions on redox potential, organic matter decomposition, and nitrogen loss in a flooded soil. Soil Biol. Biochem. 7:87-94.

8. Texas Cooperative Extension. 2004. Texas Rice Production Guidelines. B-6131. Texas Coop. Ext., College Station.

9. Wells, B. R., and Turner, F. T. 1984. Nitrogen use in flooded rice soils. In: Nitrogen in Crop Production. R. D. Hauck, ed. ASA, CSSA, and SSSA, Madison, WI.

10. Wilson, C. E., Jr., Bollich, P. K., and Norman, R. J. 1998. Nitrogen application timing effects on nitrogen efficiency of dry-seeded rice. Soil Sci. Soc. Am. J. 62:959-964.

11. Wilson, C. E., Jr., Norman, R. J., and Wells, B. R. 1989. Seasonal uptake patterns of fertilizer nitrogen applied in split applications in rice. Soil Sci. Soc. Am. J. 53:1884-1887.