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SOIL MANAGEMENT

Corn Response to Fertilizer Placement Treatments in an Irrigated No-Till System

^a USDA-ARS, Northern Grain Insects Res. Lab., Brookings, SD 57006 USA
^b Plant Science Dep., South Dakota State University, Brookings, SD 57007 USA

wriedell{at}ngirl.ars.usda.gov

	ABSTRACT

TOP NOTES ABSTRACT INTRODUCTION Materials and methods Results and discussion Conclusions REFERENCES

 
Corn (Zea mays L.) plants express unexpected K-deficiency symptoms when grown under certain conservation tillage production systems on high-K-testing soils. This field study was conducted to determine if K fertilizer treatments interact with P and N planting-time fertilizer placement treatments to affect crop growth, nutrient composition, and yield in an irrigated no-till corn production system on high-K-testing soil. The 3-yr study was conducted on Lowry silt loam soils (coarse-silty, mixed, superactive, mesic Typic Haplustolls) near Pierre, SD. Fertilizer placement (main plot) treatments consisted of P and N fertilizers that were applied with the corn planter to (i) the soil surface, (ii) the seed furrow, or (iii) a band 5 cm to the side of the seed furrow and 5 cm deep. Fertilizer products containing K, also applied at planting time, provided a with-K subplot comparison with subplots that received no added K fertilizer. Corn plants were sampled for root pull resistance, shoot dry weight, and shoot mineral nutrient composition at the tassel stage of development and grain yield. Data combined over the 3 yr of the study revealed that added K fertilizer had no effect on grain yield and did not interact with P and N fertilizer placement treatments to affect grain yield. When P fertilizer was placed with the seed and N fertilizer was placed in a 5- by 5-cm band, corn plants had 185 kg root^-1 pull resistance, 0.26 g shoot^-1 P accumulation, and 10.5 Mg ha^-1 grain yield. However, when P and N fertilizers were applied to the soil surface, corn plants had significantly less root pull resistance (151 kg root^-1), P accumulation (0.22 g P shoot^-1) and grain yield (10.1 Mg ha^-1). Added K fertilizer decreased shoot dry weight (added K = 97 g shoot^-1, no K = 103 g), decreased P accumulation (added K = 0.22 g P plant^-1, no K = 0.25 g), increased shoot N concentration (added K = 19.3 mg N g^-1, no K = 19.0 mg), and had no significant effect on K concentration or accumulation. We conclude that, although planting-time fertilizer placement was important for optimum corn growth and yield production in irrigated no-till systems, added K fertilizer did not interact with fertilizer placement to improve yield on the high-K-testing soils used in this study.

Abbreviations: W–B, W–S, B–B, S–S, fertilizer placement treatments (see Table 2)

	INTRODUCTION

TOP NOTES ABSTRACT INTRODUCTION Materials and methods Results and discussion Conclusions REFERENCES

 
MANY of the advantages of no-till corn (Zea mays L.) production are derived from the residue mulch that remains on the soil surface after grain harvest. The residue mulch protects the soil from wind and water erosion, but also delays soil warming in the spring (Swan et al., 1996). Cooler soil temperatures translate into slower seed germination, reduced uptake of nonmobile soil nutrients (especially P), and less vigorous early crop growth (Barber, 1984; Griffith and Wollenhaupt, 1994). Banded starter fertilizer application, which places the fertilizer within close proximity to the seed furrow, can help overcome these limitations to mineral nutrient uptake and early crop growth vigor (Barry and Miller, 1989). Increased fertilizer P uptake efficiency has been observed when banded P fertilizer was applied in conjunction with N fertilizer (Fan and MacKenzie, 1994). Gerwing et al. (1994) showed that planting-time P and N fertilizer applications directly in the seed furrow improved plant growth, crop nutrition, and grain yield in no-till corn production systems. Including fertilizer in the seed furrow increases the salt concentration surrounding the seed, which can under certain circumstances result in reduced seed germination and crop stand (Gelderman et al., 1998; Gerwing et al., 1994). Even with these potential problems of increased salt concentrations, however, subsurface application of P and N starter fertilizers at planting time is a popular practice among many no-till corn producers.

Under tilled conditions, application of K fertilizer to soils that test medium to high for K often results in no significant changes in grain yield compared with treatments that did not receive additional K fertilizer (Mallarino et al., 1991). Intensive corn production practices such as irrigation, increased plant populations, high-yielding hybrids, and increased N fertilizer applications increase the amount of K accumulated by the crop, which in turn may increase the requirements for K fertilizer applications to the soil (Heckman and Kamprath, 1992). Data relating N, P, and K fertilizer applications to grain yield under intensive crop and water management systems are needed to optimize fertilizer input for high corn yields (Obreza and Rhoads, 1988).

The effects of K fertilizer placement on yield of corn grown using conservation tillage methods may differ from those found for conventional-tillage corn, because the distribution of soil exchangeable K and crop roots are usually affected by the lack of tillage and the presence of the previous crop residue mulch (Yibirin et al., 1993). When no-till practices are first initiated, K fertilizer applied to the soil surface tends to accumulate in the upper soil layer, resulting in reduced crop K fertilizer use efficiency (Shear and Moschler, 1969; Moschler et al., 1972). Banding K fertilizer helps increase crop K concentration and yield in soils with low exchangeable K concentration under no-till corn production (Yibirin et al., 1993).

Under ridge-till planting systems, corn expressed unexpected K-deficiency symptoms even though soil test values were considered to be in the high or very high range (Rehm, 1995). What effect, if any, additional K fertilizer has on corn growth and yield under irrigated no-till conditions in soils that have high K soil test values is not known. The influence of K fertilizer rate and placement for crop production in conservation tillage production systems has not been researched extensively (Rehm, 1995).

Soil loss to wind and water erosion would be reduced if the number of acres farmed under no-till systems in the western U.S. Corn Belt were increased (Moldenhauer and Mielke, 1995). Research outlining the optimum placement of planting-time fertilizers under irrigated no-till conditions would help increase the likelihood that farmers would adopt this high-residue soil-conserving system. Thus, the objective of this research was to evaluate the effects of P and N planting-time fertilizer placement treatments as well as additional K fertilizer treatments on corn growth, nutrient composition, and yield in an irrigated no-till corn production system on soils that test very high for K. The experimental hypothesis was that optimum P and N planting-time fertilizer placement would interact with additional K fertilizer to increase crop growth, shoot mineral nutrient composition, and grain yield.

	Materials and methods

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Field Experiment Design and Treatments
Irrigated, no-till continuous corn plots were established in the 1990 growing season at the Dakota Lakes Research Station near Pierre, SD. The research plots were located in Lowry silt loam soils (deep, well-drained loess soils on uplands and terraces along the Missouri River; coarse-silty, mixed, superactive, mesic Typic Haplustolls) with 0 to 2% slopes. Soil tests (Gelderman et al., 1987) conducted in the spring of 1992 indicated 26 g kg^-1 organic C (loss upon combustion procedure), extractable ion concentrations of 11 mg kg^-1 NO₃–N (aluminum sulfate extraction, nitrate selective electrode procedure), 6 mg kg^-1 P (Olsen extraction, colorimetric procedure), and 225 mg kg^-1 K (ammonium acetate extraction, atomic absorption spectrophotometer procedure) in the top 18 cm (Ap horizon) of the soil profile. The soil test K value was in the very high range, and no additional K fertilizer would have been recommended for a 10 Mg ha^-1 grain yield goal (Gerwing and Gelderman, 1996).

The field study was conducted during the 1993, 1994, and 1995 growing seasons. Four planting-time fertilizer placement treatments (main plots) and two levels of planting-time K-containing fertilizer treatments (subplots) were evaluated in a split-plot experimental arrangement with four replications. The various planting-time fertilizer treatments and corn at a rate of 98000 kernels ha^-1 were applied with a five-row planter (76 cm row spacing). Fertilizer products, rates of product application, and elemental rates applied during the 3 yr of the experiment are shown in Table 1 . Main plot fertilizer treatments consisted of different combinations of N or P fertilizers applied (i) to the soil surface (dribbled in a band directly above the furrow), (ii) with the seed (directly into the seed furrow), or (iii) close to the seed furrow (banded 5 cm to the side of the furrow and 5 cm deep). Two separate K-level subplot treatments (3.8 m wide by 30 m long) were superimposed on the main-plot planting-time fertilizer placement treatments. The additional K treatment consisted of fertilizer containing K applied with the planter to the soil surface above the furrow at planting (in 1993) or applied with the N fertilizer (in 1994 and 1995). The K fertilizer products used were 2–0–14 N–P–K in 1993 and 7–21–7 in 1994 and 1995 (Table 1). Limited 2–0–14 product availability necessitated the use of 7–21–7 in 1994 and 1995. Plots that received no K fertilizer were considered to be the no additional K treatment.

Pioneer brand corn hybrid `3563' was planted on 26 April 1993, DeKalb brand corn hybrid `462' was planted on 3 May 1994, and DeKalb brand corn hybrid `493' was planted on 5 May 1995. When average soil matric potential at a depth of 45 cm reached -40 kPa, 2.5 cm of water was applied through an overhead lateral-move irrigation system. Irrigation began on 3 July 1993, 1 June 1994, and 20 June 1995. Herbicide and insecticide applications were used to manage weeds and insects as needed.

Plant Measurements
Corn plants were sampled for root pull resistance, shoot dry weight, and mineral nutrient concentration when the last branch of the tassel was completely visible (VT stage; Ritchie et al., 1992) on 28 July 1993, 15 July 1994, and 2 Aug. 1995. The force needed to pull a root system from the soil for four plants per plot was recorded using the vertical-pull technique of Ortman et al. (1968). Data collection was completed in 1 d to negate the confounding effects of changing soil moisture conditions on root pull resistance. Two randomly selected shoots per plot were cut at the soil surface, dried to a constant weight at 60°C in a forced-air oven, weighed, and ground in a Wiley mill (Arthur H. Thomas Co., Philadelphia, PA) equipped with a 1-mm screen. Ground tissue from each plot was combined and analyzed for N using the Kjeldahl method (Tucker, 1984). An inductively coupled plasma-atomic emission spectrometer (Micro-Macro International, Athens, GA) was used to measure P and K tissue concentrations. Mineral nutrient concentration data were multiplied by the shoot dry weight to determine mineral nutrient accumulation by the shoots of plants. Grain harvest was performed with a five-row combine in 1993 and 1995 (12-m passes from each plot) and by hand in 1994 (4.5 m of row). Grain weight and percent moisture were measured and used to extrapolate grain yield at a 150 g kg^-1 moisture basis.

Data Analysis
Root pull resistance, shoot dry weight, shoot mineral nutrient concentration and accumulation, and grain yield data were analyzed using analysis of variance (ANOVA) and general linear models (GLM) procedures in SAS (SAS Inst., 1988) appropriate for a split-plot experimental design conducted over three growing seasons ( = 0.1; Steel and Torrie, 1960). The model used for data analysis was based on years and replications within years as random effects and planting-time fertilizer placement and fertilizer K level as fixed effects. With the occurrence of a significant ANOVA or GLM for main effects, means were separated using the LSD option ( = 0.1; Steel and Torrie, 1960).

	Results and discussion

TOP NOTES ABSTRACT INTRODUCTION Materials and methods Results and discussion Conclusions REFERENCES

 
Growing Season
Statistical analysis revealed that almost all of the dependent variables examined were significantly affected by year. The different corn hybrids used during the study probably contributed to the significant year effects for corn nutrient composition and grain yield (Riedell et al., 1998). Diverse growing season air temperatures also could have played a major role in causing these year effects (Table 3) . The 1993 growing season was characterized by normal air temperature early, followed by much cooler than normal temperatures for the balance of the growing season. The much warmer than normal air temperatures seen early in the 1994 growing season were followed by much cooler than normal temperatures in July and August. Cooler than average temperatures in May 1995 were followed by near-normal temperatures in June and July and by warmer than normal temperatures in August. There were no significant two-way (fertilizer placement x year or additional K x year) or three-way (fertilizer placement x additional K x year) interactions for any of the dependent variables, suggesting that the subtle differences between K fertilizer products and placement (Tables 1 and 2) did not affect the dependent variables differently over the 3-yr study. Thus, data were combined over the 3 yr of the study to assess fertilizer treatments.

Fertilizer placement significantly affected grain yield. Subsurface application of P fertilizer (either with the seed or banded below the soil surface) in conjunction with N fertilizer banded below the soil surface produced significantly higher grain yield than when P and N fertilizers were placed on the soil surface (Table 4). These results agree with the observations of Fan and MacKenzie (1994), who found increased corn grain yield due to improved fertilizer P uptake efficiency when P was applied with N fertilizers in a subsurface band at planting time. Subsurface banding of P and N fertilizers also places the fertilizer below the organic matter-enriched, microbially active residue layer in a region of the soil where it is not likely to become immobilized (Mengel et al., 1982).

Additional Potassium Fertilizer
Plants grown under the additional K fertilizer treatment had significantly higher shoot N concentration at the tassel development stage than plants given no additional K fertilizers (Table 5) . Shoot mineral nutrient concentration is a single-point measurement that results from the integration of mineral nutrient absorption and dry matter accumulation (Jarrell and Beverly, 1981). Because mineral nutrient absorption and dry matter accumulation are dynamic processes, the observed increase in shoot N concentration could result if a positive factor increased N absorption or a negative factor decreased dry weight accumulation. Our data suggest that a negative factor (a detrimental effect of the additional K treatment on shoot dry weight accumulation) was responsible for the higher N concentration in the additional K treatment (Table 5). The fact that additional K fertilizer treatments had no significant effect on total N accumulated by the shoot (Table 5) supports this contention.

Additional K fertilizer treatments had no significant effect on grain yield: 10.38 Mg ha^-1 for the additional K fertilizer treatment, 10.35 Mg ha^-1 for no additional K. These results agree with those of Yibirin et al. (1993), who found that banded K fertilizer increased grain yield in soils with low soil exchangeable K levels but had no effect when soil K levels were high. The lack of significant fertilizer placement x additional K fertilizer two-way interactions or fertilizer placement x additional K fertilizer x year three-way interactions suggest that the K fertilizer treatment did not interact with fertilizer placement to affect grain yield during our experiment.

	Conclusions

TOP NOTES ABSTRACT INTRODUCTION Materials and methods Results and discussion Conclusions REFERENCES

 
We found that under irrigated no-till conditions, planting-time fertilizer treatments with P fertilizer placed in the seed furrow and the N fertilizer placed in a 5- by 5-cm band increased root pull resistance and P accumulation at the tassel stage and increased grain yield compared with P and N fertilizer treatments applied to the soil surface. Our results support and extend those of Murphy et al. (1978), who showed that deep placement of P and N fertilizers improved crop yield compared with surface application of the same materials. These results show the importance of precise P and N starter fertilizer placement for corn production under conservation tillage practices and thus support the recommendation that P and N starter fertilizers be applied in-furrow and banded for optimal corn growth, crop nutrition, and grain yield production in irrigated no-till corn production systems (Gerwing et al., 1994; Gerwing and Gelderman, 1996).

Unexpected K deficiency symptoms, which occur under ridge-till planting systems on high-K-testing soil in the northern corn belt, can be effectively eliminated by application of banded K fertilizer in the ridge (Rehm, 1995). Because our additional K fertilizer applications did not result in improved crop growth, crop nutrition, or grain yield, it is likely that this K deficiency problem does not occur under irrigated no-till conditions on high-K-test soil. Thus, corn producers that use irrigated no-till production systems on high-K-testing soil can use current soil testing methods and recommendations when designing K fertilizer applications for optimal corn growth and yield. Additional K fertilizer applications above those recommended by the soil test is not likely to be economically viable.SAS Institute 1988

	ACKNOWLEDGMENTS

 
The authors thank D. Schneider, J. Chebecek, and S. Knutson for excellent technical assistance and R.H. Gelderman, J.R. Gerwing, J.L. Pikul, and H.J. Woodard for review of an earlier version of the manuscript. Mention of commercial or proprietary products does not constitute endorsement by the USDA. USDA offers its programs to all eligible persons regardless of race, color, age, sex, or national origin.

	NOTES

TOP NOTES ABSTRACT INTRODUCTION Materials and methods Results and discussion Conclusions REFERENCES

 
Cooperative investigations of the USDA-ARS and South Dakota Agric. Exp. Stn., Brookings, SD. Journal Series no 3102.

Received for publication November 16, 1998.

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