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Production Papers

No-Till Row Crop Response to Starter Fertilizer in Eastern Nebraska

II. Rainfed Grain Sorghum

^a 279 Plant Science, Univ. of Nebraska, Lincoln, NE 68583-0915
^b INIA-Chokwe, Av. das FPLM, P.O. Box 3658, Maputo, Mozambique

^* Corresponding author (cwortmann2{at}unl.edu)

Received for publication January 10, 2005.

	ABSTRACT

TOP NOTES ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION CONCLUSIONS REFERENCES

 
Early grain sorghum [Sorghum bicolor (L.) Moench] plant growth is often slowed by cool soil temperatures in no-till production systems. This inhibitory effect may be reduced through use of starter fertilizer with a grain yield response. Twelve trials were conducted in southeastern Nebraska to determine sorghum response to different starter fertilizer nutrient combinations and placement methods at different topographic positions within locations. Soil orders at trial sites included Mollisols, Alfisols, and an Entisol. Placements of N + P and N + P + S in furrow, over the row, and 50 mm deep and 50 mm to the side of the seed (50 by 50 mm) were compared for effects on early growth, grain yield, and grain water content. Treatment by topographic position interaction effects occurred at one location for early growth and grain water content and at three locations for yield. The mean effect of starter fertilizer treatments was a 48% increase in early growth in five of seven trials with low soil test P (STP; Bray-P1 15 mg kg^–1); however, yield and grain water content responses to starter were not related to STP. Including S in the starter fertilizer did not increase yield. Placement effects were not consistently significant. The frequency and magnitude of no-till grain sorghum response to starter fertilizer were not sufficient for starter fertilizer use to be profitable, irrespective of STP and topographic position.

Abbreviations: S_as, sulfur supplied from ammonium sulfate • S_ats, sulfur supplied with ammonium thio-sulfate • STP, soil test P by Bray-1 • 50 by 50 mm, starter fertilizer placed 50 mm deep and 50 mm to the side of the seed

	INTRODUCTION

TOP NOTES ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION CONCLUSIONS REFERENCES

 
SORGHUM PRODUCTION under no-till is common in southern Nebraska. In the high-residue environments of no-till, cooler soil temperature can slow germination and root growth and reduce nutrient availability during early plant growth. Using starter fertilizer involves the application of relatively small amounts of nutrients with or near the seed, usually during planting, to accelerate early plant growth (SSSA, 1997). Studies have shown that using starter fertilizer in high-residue environments may (Gordon and Whitney, 1995) or may not (Khosla et al., 2000) increase both the early growth and grain yield of grain sorghum. Starter fertilizer may also reduce sorghum grain water content at harvest as observed for corn (Zea mays L.) (Gordon and Whitney, 2001). Probability of response to S in starter fertilizer may be greater for no-till than for tilled conditions (Woodard and Bly, 2001; Niehues et al., 2004). Response to starter fertilizer may or may not vary with soil properties such as STP (Bundy and Andraski, 1999). Woodard and Bly (2001) found topographic position to be important with corn response to application of starter fertilizer on eroded shoulder and backslope positions but not for the bottomland position, which had relatively more soil organic matter. Research results on starter fertilizer use for no-till are further reviewed in Wortmann et al. (2006).

The objective of this research was to determine grain sorghum response to starter fertilizer for different combinations of nutrients and placement methods and how these responses are affected by topographic position within fields.

	MATERIALS AND METHODS

TOP NOTES ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION CONCLUSIONS REFERENCES

 
Site Characteristics, Treatments, and Experimental Design
Trials were conducted near Pickrell (40°21' N, 96°40' W) and Beatrice (40°13' N, 96°44' W) in 2002 and near Firth (40°33' N, 96°38' W) and Beatrice (40°13' N, 96°44' W) in 2003 (Table 1). Trials were conducted on three topographic positions per location. Slopes ranged from < 1 to 5.5%. In 2002, the trial sites were on: bottomland, hilltop, and an east hillside at Pickrell and hilltop and on east and west hillsides at Beatrice. In 2003, the trial sites were on: hilltop and east and north hillsides at Beatrice and hilltop and on west and southwest hillsides at Firth. Four soil series were represented (Table 1). Continuous no-till had been practiced for at least 5 yr for all locations although in-season mechanical weed control was practiced as needed at Firth. All trial locations had a history of sorghum–soybean [Glycine max L. (Merr.)] rotation except for one trial where the previous crop was sorghum.

The hybrids used in the study were all of medium to late maturity rating for southern Nebraska and included DKC53–11 (Monsanto Co., St. Louis, MO) at Pickrell and Pioneer 84G62 (Pioneer Hi-Bred Int., Inc., Johnston, IA) at Beatrice in 2002 and Pioneer 83G66 at Firth and Pioneer 84G62 and Pioneer 83G66 at Beatrice in 2003. The cooperating producers selected the hybrid for their fields. In 2003, a second variety of similar maturity as the first was selected by the researchers and included as a split-plot treatment in the three trials at Beatrice to evaluate the hybrid x starter fertilizer treatment interaction effect.

Crop Management, Field and Plant Measurements, and Data Analysis
The base preplant N application rates were determined and applied by the cooperating producers. Nitrogen as anhydrous ammonia was applied at 118 and 112 kg ha^–1 at Beatrice in 2002 and 2003, respectively, and at 112 kg ha^–1 at Firth in 2003. At Pickrell, 112 kg N ha^–1 as urea ammonium nitrate was applied to the soil surface in 2002. No P fertilizer was applied regardless of STP except for the P in the starter fertilizer treatments. Additional planting and crop management details were as in Wortmann et al. (2006).

Field and plant measurements were largely as in Wortmann et al. (2006). Soil temperature at 0.10-m depth was monitored for 3 wk after planting for two trials each at Firth and Beatrice in 2003 using sensors (Optic StowAway Temp, Onset Computer Corp., Bourne, MA). Samples of eight plants were taken, and plants in 12 m of row were counted at V6 to V8 (Vanderlip and Reeves, 1972). A 6-m length from each of the two middle rows of the four-row plots was hand-harvested for grain yield determination. Sorghum panicles were weighed and subsampled for oven drying. Following drying and threshing, grain water content and weight were measured and used to determine yield at a 150 g kg^–1 water basis.

Surface soil samples (0 to 0.20 m) were taken at all experimental sites before planting. One sample of 10 cores of 17.5-mm diameter was collected from two replications and another from the other two replications. Soil samples were air-dried, ground, and analyzed for pH_1:1, soil organic matter, and available P and K. Organic matter was determined by loss on ignition (Nelson and Sommers, 1996). Soil test P and K were determined following the methods of Bray and Kurtz (1945) and Helmke and Sparks (1996), respectively.

Rainfall data were obtained from a station near Beatrice, NE. The station is 10.0, 32.0, and 8.4 km from the Pickrell, Firth, and Beatrice sites, respectively.

Data Analyses
Data analysis and economic analysis were as in Wortmann et al. (2006). With the exception of the Beatrice 2003 trials, analysis of variance for trials was done as a randomized complete block design. For the Beatrice 2003 trials, analysis of variance was done as a split-plot design with hybrids as subplot treatments. Treatment means by location were presented if the treatment x topographic position interaction was not significant; otherwise, treatment means are presented by topographic position within that location. The results presented for Beatrice 2003 were based on the means of the two hybrids since the hybrid x treatment interaction and the hybrid treatment x topographic position interactions were not significant. All effects were considered to be statistically significant at P 0.10 due to the applied nature of this research.

	RESULTS

TOP NOTES ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION CONCLUSIONS REFERENCES

 
Site Characteristics
Ground cover by crop residue after planting ranged from 44 to 73% (Table 1). The soils were moderately acidic for all trial sites. Soil test P ranged from low to very high (Bray-P1 > 15 mg kg^–1). Soil test K was very high (>250 mg kg^–1; Shapiro et al., 2003), and soil organic matter was >27 g kg^–1.

The respective soil temperatures on the day of planting at 0.10-m depth ranged from 13.7 to 17.9°C at Pickrell, 12.5 to 16.7°C in 2002 and 13.4 to 17.2°C in 2003 at Beatrice, and 12.3 and 16.5°C at Firth in 2003. At Beatrice and Firth in 2003, where soil temperature was monitored continuously, the daily minimum and maximum soil temperatures at 0.10-m depth during the 3 wk after planting ranged from 13 to 22°C and from 16 to 31°C, respectively, with means of 17 and 21°C (Fig. 1 ). Soil temperatures were similar for the west and southwest slopes at Firth and for the north and east slope aspects at Beatrice in 2003. Thus, any treatment x topographic position interaction effect was not likely due to soil temperature differences. Mean minimum and maximum air temperatures measured in nearby Beatrice, NE during the 3 wk after planting were 14 and 29°C in 2002 and 13 and 26°C in 2003. Rainfall was much less than normal in June and July of 2002 and in July and August of 2003 (Fig. 2 ), and soil water deficits constrained crop growth in both years at all locations.

View larger version (26K): [in this window] [in a new window]   Fig. 1. Minimum and maximum daily soil temperature at 0.10-m depth following planting in 2003 on (a) west (HSw) and southwest (HSsw) facing hillsides at the Firth location and (b) north (HSn) and east (HSe) facing hillsides at the Beatrice location. Planting dates: (a) 23 May (DOY 143) and (b) 26 May (DOY 146). The commonly accepted base temperature for sorghum is 15°C.

View larger version (38K): [in this window] [in a new window]   Fig. 2. Monthly rainfall in Beatrice, NE during the cropping seasons of 2002 and 2003.

Plant densities were not consistently affected by starter fertilizer treatments. At Beatrice in 2002, there were no differences in plant density. There was a decrease in plant density of 11.5% with an in-furrow application of starter at the 2003 locations. In contrast, there was an increase of plant densities with all placements of fertilizer at Pickrell.

Sorghum Grain Yield
The topographic position x treatment interaction affected grain yield at all locations except Firth. At Pickrell, mean yield with starter fertilizer applied was greater than for the control for only the hillside position, and yield with N + P was greater than with N + P + S at the bottomland position (Table 3). At Beatrice in 2002, starter fertilizer did not increase yield at any topographic position, but the response to N + P relative to N + P + S varied with position. Response to S source and placement also varied by topographic position at Beatrice in 2002. The position x treatment interaction at Beatrice in 2003 was attributed to lower yield with the 50- by 50-mm placement as compared with other placements at one hillside position, but otherwise there was little treatment effect at this location (Table 4). There were no treatment effects at Firth. The frequency of yield increases with starter fertilizer application was low, but increases occurred most frequently for 50- by 50-mm placement of N + P (Tables 3 and 4).

The N + P application produced higher yield than N + P + S for two trials and lower yield for another trial (Table 3 and 4). Yield was higher with S from ammonium thio-sulfate as compared with ammonium sulfate at one site. The 50- by 50-mm placement had higher yield than the mean of in-furrow and over-the-row placements for two trials and lower yield for another trial. Yield was similar for in-furrow and over-the-row placement except for one location where yield was more with over-the-row placement.

Sorghum Grain Water Content at Harvest
The treatment x position interaction effect was significant at Beatrice in 2003 due to reduced grain water with starter fertilizer applied as compared with the control at one of the hillside positions but not at the other positions (Table 5). In the hilltop trial at Beatrice in 2003, grain water content was higher with ammonium thio-sulfate as compared with ammonium sulfate as the S source. Water content was higher with over-the-row placement than with other placements for the hillside trials at this location.

	DISCUSSION

TOP NOTES ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION CONCLUSIONS REFERENCES

 
Treatment x topographic position interaction effects were significant for early growth and grain water content at Beatrice in 2003 and for grain yield at all locations except Firth. The interactions were not consistent, however, across measured traits, treatments, and combinations of treatments.

When STP < 15 mg kg^–1, starter fertilizer increased V6 to V8 biomass of grain sorghum in all but one trial. Starter fertilizer placement at 50 by 50 mm or in furrow was important to achieving increased early growth. Seminal and lateral root uptake of the surface-applied P with over-the-row application was probably too little and too late, respectively, to stimulate early growth.

In-furrow application often resulted in increased early plant growth but did not consistently affect plant density. Plant density loss with in-furrow application may be greater if water deficits occur shortly after planting, even with only 10 kg ha^–1 N applied.

Grain yield response was significant for the mean of the starter fertilizer treatments at one trial only, and this trial had relatively high STP. This contrasts with results of Gordon and Whitney (2001) where the yield increases, averaged over 3 yr, with modest amounts of N and P applied in starter fertilizer exceeded 1.6 and 1.3 Mg ha^–1 with 50- by 50-mm and over-the-row placement, respectively, on trials with very high STP and K. Increases in early growth did not consistently translate into increased grain yield. Similar results have been noted in corn (Mallarino et al., 1999).

Grain water content at harvest was reduced in 4 of 12 trials. Fertilizer N + P was as effective as N + P + S for increasing yield and decreasing grain water. The effect on grain water was less in these 12 trials than the 50 g kg^–1 decrease reported by Gordon and Whitney (2001).

Grain yield responses were determined to be sufficient to pay for the in-furrow application of starter fertilizer if yields were increased by more than 0.15 Mg ha^–1. For N + P + S applied 50 by 50 mm from the seed, yield increases of greater than 0.35 Mg ha^–1 were required (Wortmann et al., 2006). Economic grain yield response occurred most frequently with 50- by 50-mm placement of N + P and with in-furrow placement of N + P + S (Table 3 and 4). Economic response was too infrequent to confirm the profitability of any starter fertilizer treatment under these conditions, regardless of STP level. The occasional effect of reduced grain water at harvest was a small contribution toward profitability of starter fertilizer use.

It is possible that response would have been greater with earlier planting as the young plants would have been exposed to a longer period of low temperature stress. The trials were planted at typical times for grain sorghum planting in southeast Nebraska (Table 1). The frequency and magnitudes of response were less than for corn which was planted earlier than the sorghum planting dates (Wortmann et al., 2006).

The grain sorghum crops did experience soil water deficits that constrained grain yield. In both years, there was a 2-mo period during the season where the total rainfall was less than 100 mm. The long-term mean rainfall for this part of southeast Nebraska is 109, 99, and 97 mm for June, July, and August, respectively. Mean grain yields were, however, above the long-term county averages for rainfed grain sorghum (USDA-NASS, 2004) for 11 of 12 trials. Under more favorable soil water conditions, frequency and magnitude of increased grain yield might have been greater as was observed for irrigated corn in southeastern Nebraska (Wortmann et al., 2006).

	CONCLUSIONS

TOP NOTES ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION CONCLUSIONS REFERENCES

 
Early grain sorghum growth increases with application of N + P starter fertilizer are common under no-till conditions for soils with low to medium STP. Including S in the starter fertilizer may increase the frequency of early growth response. The early growth responses, however, generally do not translate into increased yield or decreased grain water content at harvest time. Increased grain yield and decreased grain water content at harvest may not be sufficient to make starter fertilizer use profitable for dryland grain sorghum. Research is needed for earlier-planted grain sorghum where seedlings are exposed to a longer period of low soil temperature.

	ACKNOWLEDGMENTS

 
This publication was made possible through support provided by the U.S. Agency for International Development, under the terms of Grant No. LAG-G-00-96-900009-00. We thank D. Scoby, A. Quincke, and M. Strnad for assisting with the research and S. Mason and C. Shapiro for their constructive reviews of the research design and trial results.

	NOTES

TOP NOTES ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION CONCLUSIONS REFERENCES

 
Contribution of the Univ. of Nebraska Agric. Res. Div., Lincoln, NE, as Journal Ser. no. 14887.

	REFERENCES

TOP NOTES ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION CONCLUSIONS REFERENCES

 

• Bray, R.H., and L.T. Kurtz. 1945. Determination of total, organic, and available forms of phosphorus in soils. Soil Sci. 59:39–45.
• Bundy, L.G., and T.W. Andraski. 1999. Site specific factors affecting corn response to starter fertilizer. J. Prod. Agric. 12:664–670.
• Gordon, W.B., and D.A. Whitney. 1995. No-tillage grain sorghum response to starter nitrogen-phosphorus combinations. J. Prod. Agric. 8:369–373.
• Gordon, W.B., and D.A. Whitney. 2001. Starter fertilizer application effects on reduced and no-tillage grain sorghum production. p. 68–72. In Kansas Fertilizer Research Progress Report 885. Kansas State Univ., Manhattan.
• Helmke, P.A., and D.L. Sparks. 1996. Measurement of soil potassium. p. 559–560. In J.M. Bigham (ed.) Methods of soil analysis. Part 3. Chemical methods. SSSA Book Ser. 5. SSSA and ASA, Madison, WI.
• Khosla, R., M.M. Alley, and P.H. Davis. 2000. Nitrogen management in no-till grain sorghum production: Rate and time of application. Agron. J. 92:321–328.[Abstract/Free Full Text]
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• Nelson, D.W., and L.E. Sommers. 1996. Loss-on-ignition method. p. 1004–1006. In J.M. Bigham (ed.) Methods of soil analysis. Part 3. Chemical methods. SSSA Book Ser. 5. SSSA and ASA, Madison, WI.
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• Shapiro, C.A., R.B. Ferguson, G.W. Hergert, A.R. Dobermann, and C.S. Wortmann. 2003. Fertilizer suggestions for corn. Available at http://ianrpubs.unl.edu/fieldcrops/g174.htm (verified 24 Oct. 2005). G74–174-A. Univ. of Nebraska, Lincoln.
• Soil Science Society of America. 1997. Glossary of soil science terms. SSSA, Madison, WI.
• [USDA-NASS] USDA National Agricultural Statistics Service. 2004. Agricultural statistics database [Online]. Available at www.nass.usda.gov/QuickStats/ (verified 25 Oct. 2005). USDA-NASS, Washington, DC.
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• Wortmann, C., S. Xerinda, M. Mamo, and C. Shapiro. 2006. No-till row crop response to starter fertilizer in eastern Nebraska: I. Irrigated and rainfed corn. Agron. J. 98:156–162 (this issue).[Abstract/Free Full Text]

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