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Dep. of Agronomy, Iowa State Univ., Ames, IA 50011-1010
* Corresponding author (malkaisi{at}iastate.edu)
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ABSTRACT |
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 TOP ABSTRACT INTRODUCTIONMATERIALS AND METHODSRESULTS AND DISCUSSIONCONCLUSIONSREFERENCES |
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Abbreviations: CP, chisel plow • CT, conventional tillage • NT, no-tillage • R6, physiological maturity stage of corn • ST, strip-tillage • V6, sixth-leaf stage of corn • V12, 12th-leaf stage of corn • VT, tassel stage of corn
Dep. of Agronomy, Iowa State Univ., Ames, IA 50011-1010
* Corresponding author (malkaisi{at}iastate.edu)
Received for publication January 6, 2007.
Understanding tillage, N, and P interactions can contribute to improved N and P utilization and crop response. This study examined the interaction effects of tillage and N rate of two N sources on N and P uptake by corn (Zea mays L.). The study was conducted on Kenyon loam (fine loamy, mixed, mesic Typic Hapludolls) soil at the Iowa State University Northeast Research and Demonstration Farm near Nashua, IA. A randomized complete block design with a split-plot arrangement in three replications was used for the two separate N source experiments. The tillage systems consist of no-tillage (NT), strip-tillage (ST), and chisel plow (CP) as main plots. Within each tillage four N rates (0, 85, 170, and 250 kg N ha–1) were assigned as subplots for each N source of manure (total N) and fertilizer (anhydrous ammonia) in a corn-soybean [Glycine max (L.) Merr.] rotation. Tillage and increase in N rate beyond 85 kg ha–1 had no effect on corn grain yield with both N sources. Tillage x N rate had a significant effect on plant N and P uptake, especially at early growth stages with both N sources. Recovery percentage of applied N across all tillage systems and N rates was 40% and 27% for manure and fertilizer sources, respectively, at the 12th-leaf growth stage of corn (V12). Plant N and P uptake at V12 growth stage was 44% and 37%, respectively, across tillage systems, N sources, and N rates. The findings indicate that the N rate and seasonal variability have more influence on plant N and P uptake than does the tillage system.
Abbreviations: CP, chisel plow • CT, conventional tillage • NT, no-tillage • R6, physiological maturity stage of corn • ST, strip-tillage • V6, sixth-leaf stage of corn • V12, 12th-leaf stage of corn • VT, tassel stage of corn
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INTRODUCTION |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTS AND DISCUSSIONCONCLUSIONSREFERENCES |
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The plant N use can be altered by the different management practices and interactions between tillage system, N rate, and N application timing. The interactive effects of different tillage systems, such as, NT, CT, or minimum tillage and N rate on grain N uptake was significant in increasing N removal with increasing N rate (Halvorson et al., 2001). Similarly, corn response to other management practices, such as the use of starter fertilizer with CT and ST systems, showed that corn silage and grain yields in CT systems were lower than those in ST; however, both silage and grain yields of both tillage systems increased with additional N applications (Mullins et al., 1998). An understanding of tillage and N source effect on the dynamics of N availability in soil and plant N uptake through the growing season at different growth stages is essential for determining the efficiency of N management. As the N availability is affected by the tillage system, P availability can equally be affected, leading to a P deficiency in many cropping systems. Many soils have large reserves of total P, but low levels of available P (Ortiz-Monasterio et al., 2002). On soils testing low in available P, application of P fertilizer or liquid manure can increase crop yields, especially for corn and soybean (deMooy et al., 1973; Mallarino et al., 1991; Obreza and Rhoads, 1988; Webb et al., 1992). However, plant P uptake varies with soil P and moisture availability, and the concentration of P in plant tissue decreases with plant age and water stress (Payne et al., 1995). It was found that banded P (deep or shallow) increased early corn growth and P uptake compared with broadcast placement with NT (Mallarino et al., 1999). Liquid manure can be a valuable source for plant P nutrient need. In a study comparing liquid swine manure with chemical N and P fertilizer sources, it was found that corn yield and N and P uptake was similar for both N sources (Al-Kaisi and Waskom, 2002).
The value of liquid manure as a nutrient source to plant growth and the proximity of such source to field crop production can help reduce the cost of corn production as producing and transporting chemical fertilizers is costly. Therefore, this research explored this alternative source for N and P. Information on tillage and N source effects on N and P use efficiency in corn is limited. Our objective was to examine the interactive effects of three tillage systems (NT, ST, and CP) and four N rates of liquid swine manure and N fertilizer on corn response and N and P use efficiencies.
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MATERIALS AND METHODS |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTS AND DISCUSSIONCONCLUSIONSREFERENCES |
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This study focused on corn response in a corn-soybean rotation. During the corn year, the 8-ha site was split into two 4-ha sites (north and south sites) for applying two sources of N. At one site (4 ha), corn received liquid swine manure, which will be referred to as manure at four different N rates based on total N (0, 85, 170, and 250 kg N ha–1), while on the adjacent 4-ha site, chemical fertilizer (anhydrous ammonia) was applied at the same N rates, which will be referred to as fertilizer.
The experimental design for each corn-N source and tillage experiment was a randomized complete block with split-plots arranged in three replications. Three tillage systems of NT, ST, and CP were randomly assigned to each replication as the main plot treatments, and the four N rates were assigned randomly to each tillage treatment as subplot treatments during each corn year. Each tillage plot was approximately 56 m long by 21 m wide, with subplots of each N rate within main tillage plots being 56 m long by 5 m wide. Each tillage treatment stayed on the same plot for the duration of the study.
In 2002, the eastern half of the experimental site was planted to corn and the western half planted to soybean. In 2003 and 2004, corn and soybean crops were planted in the order of soybean following corn on these two sites to establish the corn-soybean rotation. The soybeans were planted in a 76-cm row spacing at a seeding rate of 420,000 plants ha–1 using the same tillage treatments as in corn every year.
After harvest in mid-November of each year, CP and ST treatments were performed to both corn and soybean plots. A straight-disc coulter was used in front of the chisel points to cut through residue. Strip-tillage was performed with a six-row ST unit equipped with mole knives attached to a toolbar and centered between two 46-cm-diameter closing disks. These attachments created a 20-cm-deep tilled zone with 8-cm berms.
Each year before field application of manure, three representative liquid swine manure samples were collected in a plastic container from the manure applicator. The manure samples were mixed well and then 500-mL subsamples were collected in plastic bottles and placed in a cooler with ice for transfer to the laboratory for the same-day analysis, or were stored in a –4°C freezer. During each year, the three manure samples were analyzed individually for total C, total N, total P, total K, ammonium nitrogen (NH4–N), and nitrate nitrogen (NO3–N) concentrations using the macro Kjeldahl (Kane, 1999), AOAC-965.17 photometric method (AOAC, 1997), the EPA-7610 atomic absorption method (EPA, 1986), and the EPA-353.3 automated cadmium reduction method (EPA, 1974), respectively. Three-year averages of manure analysis were: total C, 47 g kg–1; total N, 6.8 g L–1; total P, 4.9 g L–1; total K, 4.6 g L–1; NH4–N, 5.0 g L–1; and NO3–N, 4.5 mg L–1. Each manure application rate was based on the average of the three samples of total N concentration. Each year, manure was injected 10 to 15 cm below the soil surface on 15, 23, and 27 Nov. 2002, 2003, and 2004, respectively, at the rates of 0, 85, 170, and 250 kg N ha–1 in each corn year using a Badger 5800 L manure applicator (Badger Northland, Inc., Kaukauna, WI) equipped with a modified injection knife to cause minimum soil disturbance in the same direction and location of previous rows in all tillage systems. No manure was applied after corn harvest or during the soybean season.
Anhydrous ammonia was knifed in early April of each year using a six-row, pull-type anhydrous ammonia injection knife applicator. The anhydrous ammonia was injected 10 to 15 cm deep with modified injection knives to cause minimum soil disturbance. Corn was planted on the manure and anhydrous ammonia bands in all tillage systems. During planting in May of each year, starter fertilizer was applied to the anhydrous ammonia plots by applying 29 kg P ha–1 as NH4H2PO4 and 35 kg K ha–1 as KCl, placed 5 cm deep and 5 cm from the row center.
The CP system plots were field cultivated in the spring before planting corn to control weeds and level the soil surface. In all tillage systems, corn was planted in early May of each year using DeKalb 537 non-Bacillus thuringiensis corn at a seeding rate of 84,000 plants ha–1 and 76-cm row spacing. Corn was planted over the disturbed application zone of manure and anhydrous ammonia of all tillage systems. During planting, the area was simultaneously sprayed with 189 mL ha–1 acetochlor [2-chloro-N-(ethoxymethyl)-N-(2-ethyl-6-methylphenyl) acetamide]. Corn was harvested using a combine with a scale yield monitor. Harvested corn grain was adjusted to 150 g kg–1 moisture to estimate final yield.
Crop Measurements
Plant samples of corn were collected at the sixth–leaf (V6), 12th–leaf (V12), tassel (VT), and physiological maturity (R6) growth stages for each split-plot to estimate dry matter production (Ritchie et al., 1993; Al-Kaisi and Yin, 2003). The sampling area per split-plot was 4.6 m long, which was divided into three 1.53-m segments. A separate area was maintained for yield harvest. At each of the four growth stages, one plant per 1.53-m segment of the sampling area was cut at ground level having two plants on both sides of the harvested plant. A total of three plants were cut at ground level from the 4.6-m-long row at each growth stage. Plant samples were oven-dried at 60°C for 8 d to achieve a constant dry mass. Oven-dried plant samples were ground using a Wiley Mill Model 2 carbon steel pulverizer (Arthur H. Thomas Co., Philadelphia, PA). Ground samples were placed in plastic-lined paper bags before analysis. Concentrations of total N and total P were determined by dry combustion using a LECO CHN-2000 C-N analyzer and the microwave digestion and inductively coupled plasma (ICP) method, respectively. Plant and corn grain N and P uptake were estimated as products of total plant dry matter or grain yield and their respective total N and total P concentrations.
The recovery percentages of applied N and P by grain and corn plant at different growth stages were calculated by using the following relationship:
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Late Spring Soil NO3–N Concentration
Late spring NO3–N test is a N management tool used to manage N application more efficiently. Soil samples were collected at the V6 growth stage for all treatments to measure late spring soil NO3–N concentration. A 30-cm-long soil probe with a hardened cutting tip with an inside diameter of 1.9 cm was used for soil sampling. Soil samples were collected from a 4.6-m-long row in the center of each plot. This area was divided into three 1.53-m-long sections. Soil sampling was conducted at two depths, from 0 to 30 and from 30 to 60 cm during the time of plant sampling. Ten to 12 soil cores were collected for each soil depth from each 1.53-m section of the sampling area within and between rows of each plot and kept in plastic-lined paper bags and frozen. The soil samples from each 1.53-m section were air-dried and analyzed separately for NO3–N concentration using the KCl extraction method (Mulvaney, 1996). The average of the soil NO3–N concentration of the three soil sample sections for each plot was used in data analysis.
Fall Stalk NO3–N Concentration
The fall stalk NO3–N test was used to evaluate the efficient utilization of N by corn. Nitrate-N concentration in the corn stalk was evaluated according to criteria that were established to evaluate a N fertilization program for the following season (Blackmer and Mallarino, 1996). Fall corn stalk NO3–N concentration was determined by collecting corn stalk samples from all treatments after corn reached R6 growth stage, when at least 80% of the kernels of most ears had black layer (physiological maturity) (Blackmer and Mallarino, 1996). A 20-cm-long segment of each corn stalk was taken 15 to 35 cm above ground level, and leaf sheaths were removed from samples. A total of 15 corn stalks were collected from each treatment and placed in a paper bag for drying. Corn stalk samples were oven-dried at 60°C for 8 d to attain a constant dry mass before grinding with the carbon steel pulverizer. The ground corn stalks were sealed in plastic-lined paper bags for storage before analysis. Samples were analyzed for corn stalk NO3–N concentrations using the 2M potassium chloride (KCl) extraction method (Mulvaney, 1996) using a Lachat QuickChem FAI+8000 series with cadmium reduction column. Corn stalk nitrate concentrations were expressed as mg NO3–N kg–1 of dry corn stalk.
Statistical Analysis
Statistical analysis of the data was performed using a statistical analysis system package (SAS Institute, 2003). Data from each N-source experiment were analyzed separately for the main and interaction effects between year, tillage, and N rate by using the GLM procedure for analysis of variance appropriate for a randomized complete block design with a split-plot arrangement. Mean separations were performed by using the least significant difference (P 
0.05). The interaction effects of treatments were presented for both N sources.
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RESULTS AND DISCUSSION |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTS AND DISCUSSIONCONCLUSIONSREFERENCES |
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Tillage and N Rate Effects on Grain Recovery of Applied N and P
The grain recovery of applied N from both N sources was generally greater with the 85 kg N ha–1 rate compared with the other two higher application N rates in all tillage systems (Table 3
). However, it was observed that both ST and CP improved grain N recovery, especially with manure source at the 85 kg N ha–1 rate. The increase in N application rate beyond 85 kg N ha–1 did not increase grain N recovery with all tillage systems. It was observed that grain N recovery of applied N fertilizer with NT was greater compared with ST and CP at 85 and 170 kg N ha–1 rates. These finding are consistent with those by Al-Kaisi and Waskom, 2002. It appears that the increase in N rate beyond 85 kg N ha–1 did not contribute significantly to recovering applied N with both N sources regardless of tillage system. The grain P recovery was significantly greater with CP treatment compared with the NT or ST with manure at 85 kg N ha–1 rate. The increased amount of applied P with manure did not lead to greater grain P recovery, where manure N rate application was based on total N content.
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Effects of Tillage, N Rate, and Season Interactions on Grain N and P Uptake and Recovery
Interaction effects of tillage x N rate, tillage x year, and N rate x year on grain N and P uptake were frequently observed with both N sources, although inconsistent (Table 4
). The only significant interaction between tillage and N rate was observed with grain N uptake for the fertilizer source. The tillage x year interaction had a significant effect on grain N and P uptake of manure source and on grain N uptake with fertilizer source. However, the N rate x year interaction had a significant effect on grain N and P uptake with manure and fertilizer sources, respectively (Table 4). Even though these interactions are inconsistent with both N sources, they reflect the seasonal variability effect on grain N and P uptake with different tillage systems. Generally, there was an insignificant three-way interaction of tillage x N rate x year effect on grain N and P uptake with both N sources. These finding are consistent with observations described by Dharmakeerthi et al. (2006), where N fertilizer level and tillage interaction effect was not significant during any growth stage.
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In the fertilizer source plots, the tillage effect on plant N uptake with different N rates was highly variable during all growth stages (Table 7 ). At the V6 to R6 growth stages, the difference in plant N uptake was only significant between zero and high N rates across all tillage systems. It was noticeable at the VT growth stage that a maximum N accumulation was reached and greater plant N uptake was observed at all fertilizer N rates for the CP tillage system, except at the 250 kg N ha–1 (Table 7).
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The plant N uptake at the V12 growth stage across all tillage systems was calculated as a percentage of total N uptake (grain + plant) using data from Tables 2 and 6 for manure source; the N uptake was 42, 41, 50, and 43%, for 0, 85, 170, and 250 kg N ha–1 N rates, respectively. Similarly, N uptake was calculated as a percentage of total N uptake (grain + plant) using data from Tables 2 and 7 at the V12 growth stage across all tillage systems with fertilizer source; the N uptake was 41, 44, 47, and 41% for 0, 85, 170, and 250 kg N ha–1, respectively. The P uptake at the V12 growth stage across all tillage systems as a percentage of total P uptake (grain + plant) was 37, 42, 41, and 36%, and 35, 33, 36, and 33% for the above N rates of manure and fertilizer N sources, respectively.
Tillage and N Rate Effects on Plant Recovery of Applied N and P at Different Growth Stages
The recovery of applied N and P from both manure and fertilizer sources by corn plant progressively increased with corn growth through VT growth stage (Tables 8
and 9)
. However, the greatest N recovery was observed at the 85 kg N ha–1 N rate across all tillage systems with both N sources at the VT growth stage (Tables 8 and 9). Generally, increased N rate resulted in a decrease in plant N and P recovery with all tillage systems.
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Effects of Tillage, N Rate, and Season Interactions on Plant N and P Uptake and Recovery
The interactions of tillage x N rate, tillage x year, and N rate x year had a significant effect on plant N and P uptake during the early growth stage (V6), but tillage x N rate x year had only a significant effect on plant P uptake with fertilizer source (Table 4). Changes in soil conditions because of different tillage along with seasonal variability may contribute to the change in N and P availability early in the growing season. Thus, a significant tillage effect on plant N uptake could often be observed during the early parts of the growing season (Dharmakeerthi et al., 2006). The interaction effect of tillage x N rate, tillage x year, and N rate x year after the V6 growth stage on plant N and P uptake was inconsistent with both N sources. These interaction effects on plant N and P uptake were insignificant, particularly late in the season where tillage systems have very limited effect on plant N or P uptake. These observations are similar to those by Dharmakeerthi et al. (2006), where plant N uptake between V6 growth stage and silking is not significantly affected by tillage system. The few cases of increase in plant N and P uptake that were observed with CP tillage system with both N sources is highly related to soil temperature increase and enhanced early plant growth compared with NT (data not presented). The cool soil conditions associated with the NT system tend to reduce early plant growth and nutrient uptake (Licht and Al-Kaisi, 2005b; Kaspar et al., 1990). It was observed that at the R6 all interactions of tillage, N rate, and year in affecting plant N and P uptake were inconsistent with both N sources. Tillage x N rate and N rate x year were significant at the R6 growth stage in affecting plant N and P uptake with manure source, and only N rate x year was significant in affecting plant N uptake with fertilizer source (Table 4). The three-way interaction of tillage, N rate, and year had a significant effect on plant P uptake at the V6 growth stage with fertilizer N source and at the R6 growth stage with both N sources (Table 4). These interactions indicate that the N rate and seasonal variability have more effect on plant N and P uptake later in the growing season than the tillage system. Dharmakeerthi et al. (2006) found that N uptake was affected by fertilizer N management during the V6 growth stage to maturity.
The only significant interaction in affecting plant N and P recovery of applied N and P was tillage x N rate at the V6 growth stage with both N sources (manure and fertilizer). It was observed that 31, 13, and 69% of the two-way interactions of tillage x N rate, tillage x year, and N rate x year, respectively, have a significant effect (P < 0.05) on N and P recovery from V6 to R6 growth stages (Table 5). However, only 25% of the three-way interaction effects of tillage x N rate x year on N and P recovery were significant (P < 0.05) from V6 to R6 growth stages (Table 5).
Tillage and N Rate Effects on Fall Corn Stalk NO3–N Concentration
Three-year averages of fall corn stalk NO3–N concentration increased linearly with increasing N application rate with both N sources regardless of tillage system (Fig. 1a
and 1b). The relationship between corn stalk NO3–N concentration and N application rate within each tillage system of both N sources is well described by linear functions, but not significantly different in slopes with manure source. This relationship also explains the effect of each tillage system on potential NO3–N accumulation in corn stalks at maturity, where corn stalks had similar NO3–N concentrations (Fig. 1a). The slopes of linear functions with manure source are not significantly different (P < 0.05), which means the rate of NO3–N accumulation is identical with all tillage systems. Fall stalk NO3–N concentration and slope were highest in the ST system for the fertilizer source at the 170 and 250 kg N ha–1 N rate compared with NT and CP (Fig. 1b).
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Tillage and N Rate Effects on Late Spring Soil NO3–N Concentration
The relationship between soil NO3–N concentration in the top 30 cm of soil and N rate of manure and fertilizer sources of 3-yr averages of the three tillage systems was poorly described by a linear function (P < 0.05), except for NT with manure source and ST with fertilizer N source (Fig. 2a
and 2b). The relationship was equally poorly described by nonlinear function as well (data not presented). The weak relationship between soil NO3–N concentration and N rate is most likely due to high spatial variability of soil NO3–N concentration. The slopes of the linear functions of the three tillage systems with manure are similar (P < 0.05) (Fig. 2a), which indicates a similar effect of all tillage systems on NO3–N concentration in soil. However, differences in slopes of different tillage systems were more pronounced with fertilizer source, where it was greater with ST compared with both NT and CP slopes (P < 0.05) (Fig. 2b). The concentration of NO3–N was low during early spring in 2002 and 2004, which is most likely caused by some deep leaching of NO3–N due to above normal rainfall in early April (approximately 2.70 cm) (local weather station at the research farm). At all manure N rates, tillage systems did not cause significant differences in late spring soil NO3–N concentration (Fig. 2a). Soil NO3–N concentration of ST with fertilizer source was greater than that under both the NT and CP systems at the N rates of 170 and 250 kg N ha–1 at the top 30 cm (Fig. 2b). The high spatial and seasonal variability effect on soil NO3–N concentration with both manure and fertilizer sources with all tillage systems is very evident and clearly highlights the inconsistency of tillage effect on NO3–N status, and therefore, the reliability of this test for N application recommendations.
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CONCLUSIONS |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTS AND DISCUSSIONCONCLUSIONSREFERENCES |
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The tillage x N rate effect on plant N and P recovery was only significant at the V6 growth stage with both N sources. However, most dominant interaction effect on plant N and P uptake and recovery was N rate x year from the V6 to R6 growth stages. This significant interaction effect on plant N and P uptake and recovery was consistent with both N sources at the V6 and R6 growth stages. This indicates that seasonal variability has more effect on N availability than the type of tillage system. The three-way interaction effect of tillage x N rate x year on plant N and P recovery was generally insignificant, and only 25% of this interaction was significant from the V6 to R6 growth stages.
Regardless of N source, the interaction effect of tillage x N rates influenced both corn stalk NO3–N and soil NO3–N concentrations. Generally, the relationships between either corn stalk NO3–N concentration and the N application rate of both N sources was linear, increasing with the increase of N rate in all tillage systems. The soil NO3–N and N rate showed a poor correlation due to high spatial variability of soil NO3–N concentration. The interaction between tillage and N rate was inconsistent in influencing plant N and P uptake by corn plant and grains, but high N rates have an influence on yield response and corn stalk NO3–N concentration regardless of the tillage system. The findings suggest that both N sources have a similar effect on yield and N and P uptake regardless of tillage type. Additional N application from both N sources did not increase N uptake or yield for one particular tillage system over another. The findings of this study also indicate that the most effect a tillage system can have on plant N and P uptake was early in the growing season with both N sources, and it had a limited effect on plant N and P uptake later in the growing season. It was always believed that NT might have a disadvantage in nutrient availability and the need for additional N and P applications compared with CT systems. However, these findings showed the limited effect that increased N or P application has on increasing the utilization or recovery of these two nutrients by corn grown with all tillage systems. Furthermore, the most dominant or significant two-way interaction effect on plant N and P uptake or recovery was N rate x year rather than tillage x N rate or tillage x year interactions. Another interesting observation from these results is the similarity of nutrient value of both N sources and corn response to these two N sources across all tillage systems.
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REFERENCES |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTS AND DISCUSSIONCONCLUSIONSREFERENCES |
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a, W.H. Pfeiffer, and A.H. Hede. 2002. Phosphorus use efficiency, grain yield and quality of triticale and durum wheat under irrigated conditions. Proc. of the 5th Int. Triticale Symp., Annex. 30 June–5 July 2002. Radzików, Poland.This article has been cited by other articles:
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  A. Meyer-Aurich, M. Gandorfer, G. Gerl, and M. Kainz Tillage and Fertilizer Effects on Yield, Profitability, and Risk in a Corn-Wheat-Potato-Wheat Rotation Agron. J., November 1, 2009; 101(6): 1538 - 1547. [Abstract] [Full Text] [PDF]
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