SSSAJ Grow Your Career with SSSA
HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
QUICK SEARCH:   [advanced]


     

This Article
Right arrow Abstract Freely available
Right arrow Figures Only
Right arrow Full Text (PDF) Free
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Similar articles in this journal
Right arrow Similar articles in ISI Web of Science
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrow reprints & permissions
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via ISI Web of Science (11)
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Rozas, H. R. S.
Right arrow Articles by Picone, L. I.
Right arrow Search for Related Content
PubMed
Right arrow Articles by Rozas, H. R. S.
Right arrow Articles by Picone, L. I.
Agricola
Right arrow Articles by Rozas, H. R. S.
Right arrow Articles by Picone, L. I.
Related Collections
Right arrow Other Soil Management
Right arrow Tillage
Right arrow Soil Analysis
Soil Science Society of America Journal 65:1314-1323 (2001)
© 2001 Soil Science Society of America

DIVISION S-8—NUTRIENT MANAGEMENT & SOIL & PLANT ANALYSIS

Denitrification in Maize Under No–Tillage

Effect of Nitrogen Rate and Application Time

Hernán R. Sainz Rozas, Hernán E. Echeverría* and Liliana I. Picone

Facultad de Ciencias Agrarias (U.N.M.P.)-Estación Experimental Agropecuaria Balcarce (I.N.T.A.), Unidad Integrada Balcarce, C.C. 276, (7620) Balcarce, Buenos Aires, Argentina

* Corresponding author (E-mail: hecheverr{at}balcarce.inta.gov.ar)


   ABSTRACT
TOP
 ABSTRACT
INTRODUCTION
 MATERIALS AND METHODS
 RESULTS AND DISCUSSION
 CONCLUSION
 REFERENCES
 
Denitrification N losses from soils under no-tillage (NT) can reduce N-use efficiency and destroy the ozone layer if appreciable amounts of N oxides (N2O, NO) are lost. The objective of this study was to evaluate the effect of surface-applied urea rate (0, 70, and 210 kg N ha-1) and different application times [planting (PL) and six-leaf stage (V6)] on denitrification losses (DLs) in NT irrigated maize (Zea mays L.). The field experiment was carried out in the 1996 and the 1998 growing seasons, at Balcarce (37°45'S; 58°18'W), Argentina, on a Typic Argiudoll and a Petrocalcic Paleudoll. The annual mean rainfall in the area is 870 mm and annual mean temperature is 13.7°C. Denitrification rates (DRs; N2O) were measured using C2H2 blockage core method. The DRs were highest between PL and the V6 because of higher water filled pore space (WFPS), and were closely associated with the WFPS (r2 equal to 0.66 and 0.76 for 1996 and 1998, respectively). On average, accumulated DLs for the PL application were 7.6 and 9.8 kg N2O–N ha-1 (5.5 and 2.6% of N applied for 70 and 210 kg N ha-1, respectively). However, for application at the V6, accumulated DLs were 2.0 and 2.1 N2O–N kg ha-1 (1.0 and 0.4% of N applied for 70 and 210 kg N ha-1, respectively). The results indicate that for this soil and climatic zone, denitrification N losses were greater when the fertilizer was applied at PL than when fertilizer was applied at the V6.

Abbreviations: CT, conventional tilling, DL, denitrification loss • DR, denitrification rate • GLM, general linear model • LSD, least significat difference • NT, no-tillage • PL, planting • TF, treatment fertilized • V6, six-leaf stage • WFPS, water filled pore space


   INTRODUCTION
TOP
 ABSTRACT
 INTRODUCTION
MATERIALS AND METHODS
 RESULTS AND DISCUSSION
 CONCLUSION
 REFERENCES
 
NO-TILLAGE SYSTEMS leave crop residues on the soil surface, reducing soil erosion, and increasing crop water-use efficiency (Blevins et al., 1977). However, maize N uptake and grain yield at low N rates can be lower than those in soils under conventional tillage (CT) (Meisinger et al., 1985). This behavior is probably because of a greater N immobilization and NO3 leaching in soils under NT compared with those under CT (Thomas et al., 1973; Kitur et al., 1984).

Surface urea applications under NT have a low efficiency because of potential NH3 volatilization losses (Keller and Mengel, 1986; Sainz Rozas et al. 1997a). Another gaseous loss mechanism that can reduce N-use efficiency in soils under NT is denitrification. Denitrification is a biological process by which NO3 and NO2, under anaerobic conditions, are reduced sequentially through NO and N2O to N2. No-tillage systems, often characterized by an accumulation of crop residues on the soil surface, results in greater C, N, and water content in the upper 5- to 10-cm of soil compared with CT (Blevins et al., 1977; Doran, 1980). Consequently, facultative anaerobes and denitrifying bacteria are more numerous in NT soils (Doran, 1980), and therefore, higher DRs have been reported in NT soils than in plowed soils (Rice and Smith, 1982; Linn and Doran, 1984).

In 15N studies conducted on maize crop under CT, Olson (1980) and Reddy and Reddy (1993) reported that between 15 and 25% of N applied at PL was not recovered in the soil–plant system, and presumably lost via denitrification. However, direct evaluation of DL with the C2H2 inhibition technique on maize crop under CT, indicates that only 4.7 to 7.4% of the N applied was lost by denitrification when this nutrient was applied at PL (Liang and MacKenzie, 1997) and 0.6 to 3.2% was lost when fertilized at the V6 (Duxbury and McConnaughey, 1986; Bronson et al., 1992; Qian et al., 1997). The magnitude of DL is undoubtedly a function of various soil properties and environmental factors that control the DR in soil, such as water content, available C, NO3 concentration (which is increased by N fertilization), pH, and temperature (Aulakh et al., 1992).

The DR increases abruptly if the WFPS exceeds a certain critical level, which varies between 70 and 80% (Doran et al., 1990). On the other hand, the DR can be limited by soil NO3–N concentrations lower than 40 mg N kg-1 soil (Bowman and Focht, 1974; Kohl et al., 1976; Knowles, 1981). Balcarce (southeastern Buenos Aires Province, Argentina) is characterized by a temperate–humid climate, with rainfall higher than evapotranspiration in early spring (Suero, personal communication, 1998). Also, in this area, soil surface (0–20-cm depth) NO3-N concentrations at PL are generally low (7–10 mg N kg-1 soil) in NT continuous maize (Sainz Rozas et al., 1999). Therefore, the WFPS could be higher than the mentioned critical level in early spring, and consequently, if N is applied at PL, DL could be important, especially when high N rates are applied. On the contrary, after the V6, regardless of the N rate, the denitrification process could be severely limited by soil water content, because active growth of maize after this stage substantially increases evapotranspiration (Andrade et al., 1997).

A higher fertilizer N-recovery efficiency with urea applied at the V6 compared with fertilization at PL has been reported for NT irrigated maize crops in Balcarce (Sainz Rozas et al., 1997b). In this study, apparent N recovery (average N rates) was 71 and 58%, for fertilizations at the V6 and PL, respectively (Sainz Rozas et al., 1997b). However, it is not known if greater DL early in the growing season for these conditions was the main factor reducing N-use efficiency when N was applied at planting.

No-tillage maize is becoming a very important crop in the Balcarce. A better understanding of N-cycling processes in NT maize crops, particularly the microbial conversion of plant available N to gaseous N forms, is needed for most efficient use of N fertilizer. This would contribute to minimizing the risk of degradation of the environmental through DLs in this tillage system, which is characterized by high N requirements.

The objective of this study was to evaluate the magnitude of the DL in NT irrigated maize as a function of N rate and application time (PL or V6).


   MATERIALS AND METHODS
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
RESULTS AND DISCUSSION
 CONCLUSION
 REFERENCES
 
The experiment was conducted during the 1996–1997 and the 1998–1999 growing seasons on a soil complex of a fine, mixed, thermic Typic Argiudoll and a fine, illitic, thermic Petrocalcic Paleudoll (petrocalcic horizon was below 0.7 m) at Instituto Nacional de Tecnologia Agropecuaria (INTA) Research Station, Balcarce (37°45'S lat.; 58°18'W long.; 130 m above sea level), Buenos Aires, Argentina. The surface horizon (0–20-cm depth) of this soil has an organic matter content of 58.4 g kg-1 (Walkley and Black, 1934), loam texture (Gee and Bauder, 1986), 33.4 cmolc kg-1 cation-exchange capacity (Chapman, 1965), and pH of 5.85 (determined with a glass electrode in a suspension of 1:2.5 soil/water ratio). Since 1994, maize was grown under NT at the experimental site. The site was maintained in a cropping system under CT for the previous years. Ground cover with maize residue ranged between 80 and 90% in both growing seasons. One, red, flint, single cross maize hybrid, Dekalb 639 (1540°C, days from emergence to physiological maturity) was used for both growing seasons. Heat units were calculated according to the residual method (Cross and Zuber, 1972) using a base temperature of 8°C (Andrade et al., 1999). Distance between the crop rows was 0.7 m, and the final plant population was 79 000 and 73 500 plants ha-1 for the first and second growing season, respectively. Plots were 12 m long and five rows wide (42 m2). The plots were fertilized annually at planting with 20 kg P ha-1 and sprinkle irrigated during high water requirement periods so that these production factors did not limit crop growth.

In both growing seasons, a factorial combination of two N rates (70 and 210 kg N ha-1) and two fertilization times (PL and V6) were combined to generate four treatments, to which a control was added (0-N). The experimental design was a randomized complete block with three replications. In all cases, urea was surface broadcast.

The DRs were generally estimated weekly or biweekly during the growing season. If a rainfall happened or an irrigation was carried out, the frequency was altered because sampling schedules based on integration of DRs must include these events to obtain meaningful estimates of N loss (Sexstone et al., 1985). In the first growing season, measurements started 13 d after planting (5 d after fertilization) and ended at the V6 for fertilization at PL. For V6 fertilization, measurements started 54 d after planting (8 d after fertilization) and finished at flowering. Both periods lasted 39 d. In the second growing season, measurements started 10 d after planting (4 d after fertilization) and finished at physiological maturity for fertilization at PL, while for V6 fertilization, measurements started 59 d after planting (5 d after fertilization) and finished at physiological maturity. Denitrification rates (N2O–N) under field conditions were estimated by the C2H2 inhibition method (Yoshinari et al., 1977). Six intact soil cores (4.2-cm i.d. by 15 cm long) were randomly obtained from between rows in each plot using polyvinyl chloride cylinders. The cylinders were sealed with two rubber stoppers with the upper stopper having a septum. Ten percent (v/v) of the gas enclosed in the cylinder was replaced with an equivalent volume of acetylene. Then, cylinders were incubated outside the laboratory in an open, but shaded environment for a 24-h period, after which, a 10-mL gas sample was removed for analyses of N2O–N. The gas samples were kept at 4°C in evacuated plastic sampling vials until their analysis. The concentration of N2O–N was determined using a 5890 series-II Hewlett-Packard (Palo Alto, CA) gas chromatograph equipped with a 63Ni electron-capture detector (Mosier and Mack, 1980). The carrier gas (N2) flowed at a rate of 15 mL min-1, while the detector, oven, and injector temperatures were of 300, 35, and 50°C, respectively.

In each denitrification sampling date, two soil samples were collected (0–15-cm depth) beside each cylinder (12 soil cores per plot), pooled and mixed for determination of NO3–N and gravimetric moisture content. Inorganic N was extracted from fresh samples with K2SO4 (0.5 M) in ratio 1:4 of soil/K2SO4, and NO3–N content was determined by steam distillation (Bremner and Keeney, 1966).

Water-filled pore space was calculated as:

(1)
where soil porosity is

(2)
with 2.65 Mg m-3 as the assumed particle density of soil. The bulk density was determined by the cylinder method (Blake and Hartge, 1986). In both growing seasons before planting, eight undisturbed soil cores (5-cm diam. by 5-cm length) were taken from each block (5–10-cm depth). The soil bulk density average was 1.35 Mg m-3.

A laboratory study was designed with the objective of evaluating the effects of C and soil NO3–N availability on DRs. The undisturbed soil cores were obtained from the 0- to 15-cm depth at the 17 (10 Oct. 1998) and 117 d after maize planting (1 Feb. 1999), from the plots fertilized at planting with 0 and 210 kg N ha-1. In the laboratory, the soil water content was adjusted to 87 and 94% WFPS for the first and second sampling, respectively, by adding a KNO3 solution (100 mg N kg-1 soil), glucose solution (500 mg C kg-1 soil), and a NO3 and glucose solution. Ten percent (v/v) of the gas enclosed in the cylinder was replaced with an equivalent volume of acetylene. Then cylinders with the amended cores were incubated for a 24-h period at room temperature in the laboratory. At the end of incubation, 10-mL gas samples were removed for analysis of N2O–N as described above. The experimental design was a split plot with three replications. Nitrogen rates (0 and 210 kg N ha-1) were the main plot treatments, KNO3, KNO3 and glucose solution, and glucose, were the subplot treatments. Values for denitrification were calculated as means of duplicate determinations on each treatment.

Cumulative DLs were estimated for each plot by integrating the area under the curve of daily fluxes over the time by Simpson's rule. Prior to any statistical analysis, DRs were checked for normality (P = 0.05) using the Shapiro–Wilk test (Shapiro and Wilk, 1965). If normal distribution was not met, DRs were log-transformed (Parkin and Robinson, 1994). The data were statistically analyzed by ANOVA and general linear model procedure (GLM) of the SAS Institute (1985). Least significant differences (LSD) at the 0.05 level were calculated when the F-statistic between treatments or their interaction was significant. Slopes of linear regressions were compared using T-test at the 0.05 probability level. A plateau-and-linear model, as that utilized by Doran et al. (1990), was used to describe the relationships between DRs and WFPS, and was fitted using the NLIN procedure of the SAS Institute Inc. (1985). Cumulative DLs expressed as a percentage of the N applied were calculated by subtracting the control values (0–N) from the values measured in N treatments.


   RESULTS AND DISCUSSION
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS AND DISCUSSION
CONCLUSION
 REFERENCES
 
Nitrous Oxide Emission Patterns
The coefficients of variation of DRs during the first and second growing season ranged between 32 and 117%, and between 30 and 71%, respectively. This variability was similar to that reported by Mosier et al. (1986). In both growing seasons, the DRs were highest during the period lapsed between planting and the V6. Denitrification rates were significantly increased (P < 0.05) in most sampling dates by increasing N rate, and consequently, the soil NO3–N content (Fig. 1 and 2). Although the soil N content was significantly increased (P < 0.05) by N addition, DRs between the V6 and flowering in 1996–1997 growing season, were not affected by N rate. In the period between the V6 and physiological maturity in the 1998–1999 growing season, the DRs were not influenced by either N rates or application time (Fig. 1 and 2).



View larger version (24K):
[in this window]
[in a new window]
  		Fig. 1. Denitrification N losses in no-tillage irrigated maize as a function of N rates and application times in the 1996–1997 and 1998–1999 growing seasons. 0–N is the control; 70, and 210 is kg N ha-1; P is fertilization at planting; V6 is fertilization at the six-leaf stage; F is flowering; PM is physiological maturity. Asterisks indicate significant effect (P <= 0.05) of the N rate on denitrification rates log-transformed.

 


View larger version (26K):
[in this window]
[in a new window]
  		Fig. 2. Soil NO3–N content at 0- to 15-cm depth during 1996–1997 and 1998–1999 growing seasons in no-tillage (NT) irrigated maize, for urea fertilization at maize planting (P) and at the six-leaf stage (V6). 0–N is the control; 70 and 210 is kg N ha-1; F represents flowering; PM is physiological maturity. Asterisks indicates significant effect (P <= 0.05) of N rate on soil NO3–N concentration.

 
The greatest soil water content and WFPS were generally observed during the period lapsed between PL and the V6 in both growing seasons (Fig. 3 and 4). The greatest soil water content and WFPS are in agreement with Andrade et al. (1997) who reported that water loss by evapotranspiration during this period are low, especially in maize crop under NT. In both growing seasons, the highest DRs were measured when both the soil NO3–N content and the WFPS were high. A positive and nonlinear association (P < 0.01) between DR and WFPS was found (Fig. 5). These data are comparable with those reported by Mahmood et al. (1998) for maize crop under CT, which would indicate that WFPS is a very important factor to establish denitrification capacity in summer crops like maize. Figure 5 shows that most DR values corresponding to the fertilization at the V6 were located below the determined WFPS threshold. This behavior indicates that the denitrification process was severely limited by the soil water content after the V6 although significant rainfall and irrigation happened after the V6 in both growing seasons (Fig. 3 and 4). On average of sampling dates and treatments, the WFPS was 72 and 69% for 1996 and 1998, respectively. Low soil water content is associated with high maize water consumption after the V6 (Andrade et al., 1997). These results agree with those reported by Aulakh et al. (1984a) and Liang and Mackenzie (1997), who working with wheat (Triticum aestivum L.) under NT and maize under CT, respectively, found that the largest DLs occurred early in the growing season and were associated with high soil water content.



View larger version (25K):
[in this window]
[in a new window]
  		Fig. 3. Soil water filled pore space (WFPS) and rainfall (continuous bars) plus irrigation (dashed bars) during 1996–1997 growing season in no-tillage maize. P represents urea applied at planting; V6 represents urea applied at the six-leaf stage (V6). 0–N is the control; 70 and 210 is kg N ha-1; F represents flowering.

 


View larger version (25K):
[in this window]
[in a new window]
  		Fig. 4. Soil water filled pore space (WFPS) and rainfall (continuous bars) plus irrigation (dashed bars) during 1998–1999 growing season in no-tillage maize. P repesents urea applied at planting; V6 represents urea applied at the six-leaf stage (V6). 0–N is the control; 70 and 210 is kg N ha-1; F represents flowering; PM represents physiological maturity.

 


View larger version (24K):
[in this window]
[in a new window]
  		Fig. 5. The relationship between denitrification rate (DR) and water filled pore space (WFPS) in no-tillage irrigated maize during 1996–1997 and 1998–1999 growing seasons. Full and empty symbols correspond to fertilization at planting (P) and at the six leaf stage V6, respectively. 0–N is the control; 70 and 210 eqauls kg N ha-1.

 
In both growing seasons, a positive and linear association (P < 0.05) between the DR (corresponding to the treatments with and without N) and the WFPS for values greater than 82% was found (Fig. 6). However, the slope of relationship for the treatment without N was significantly lower (P < 0.05) than that of the treatments with N (Fig. 6). These results indicate that in the treatment without N, which had soil NO3–N concentration ranging between 6.4 and 17.7 mg kg-1 in both growing seasons (Fig. 2), the denitrification process may have been limited by N availability. These results are consistent with previously reported research (Bowman and Focht, 1974; Kohl et al., 1976; Knowles, 1981), which indicated that the denitrification process is limited by soil NO3–N concentrations lower than 40 mg kg-1. However, under natural conditions, where factors such as water content, C availability, and NO3–N concentration are interrelated, the soil NO3–N concentration often does not show a significant correlation with the DLs (Aulakh et al., 1983a; Aulakh et al., 1983b; Aulakh et al., 1984b).



View larger version (19K):
[in this window]
[in a new window]
  		Fig. 6. The relationship between denitrification rate and water filled pore space (WFPS) for treatments fertilized (TF) at planting with 70 and 210 kg of N ha-1 (empty symbols) and for treatment control (0–N; full symbols).

 
Denitrification Accumulated Losses
In both growing seasons, there was a significant interaction (P < 0.05) between the N rate and the fertilization time on N2O–N accumulated losses. The N rate increases the accumulated DLs mainly when N was applied at PL (Table 1). When N was applied at PL, the accumulated DLs for the highest N rate (210 kg N ha-1) were on average (for both growing seasons) 31% > DLs with an N rate of 70 kg N ha-1 (Table 1). Despite the interaction detected, in both growing seasons, the accumulated DL for fertilization at PL were significantly higher (P < 0.001) than those for fertilization at the V6 (Table 1). For fertilization at PL, in the 1996–1997 growing season, the accumulated DLs were 4.2 and 2.4% of N applied for the N rates of 70 and 210 kg N ha-1, respectively. In the 1998–1999 growing season, the accumulated DLs were 6.9 and 3.4% of N applied for the N rates of 70 and 210 kg N ha-1, respectively (Table 1). Accumulated losses during the whole 1998–1999 growing season for the treatments fertilized at planting were 7.0 and 3.8% of the N applied (data not shown), which reflects that almost all of the losses were measured between planting and the V6. The accumulated DLs between planting and the V6 were greater than those of previously reported studies (Mosier et al., 1986; Liang and MacKenzie, 1997; Qian et al., 1997) for maize crop under CT. This difference can be explained by the greater denitrification potential of soils under NT compared to soils under CT (Doran, 1980; Rice and Smith, 1982; Linn and Doran, 1984). However, in both growing seasons, when the urea was applied at the V6, the accumulated DLs (as a percentage of N applied) ranged between 0.03 and 1.07% (Table 1), and were similar or lower than those reported by Duxbury and McConnaughey (1986), Bronson et al. (1992), and Qian et al. (1997) for irrigated maize crop under CT. Our results indicate that despite greater potential denitrification N losses of NT soils, if N is applied during the most active growth period of maize, which substantially increases water consumption, the denitrification N losses are very low.


View this table:
[in this window]
[in a new window]
  		Table 1. Analysis of variance of denitrification accumulated losses during 39 d after planting and six-leaf stage (V6) in no-tillage irrigated maize as affected by N rates and application times.

 
Effect of Nitrate and Available Carbon on Denitrification Rate
The effect of the N rate and the soluble N and C on DRs from soil samples taken 17 and 117 d after planting is shown in Table 2. In this Table, only the main effects are shown because in both sampling dates, there was not significant interaction between the N rate and the soil cores amended with soluble N and C. In the sampling carried out at 17 d, the soil NO3–N concentrations for treatment without N and with 210 kg N ha-1 were 7.8 and 49.6 mg kg-1, respectively (Fig. 2). The DR for the treatment with N was significantly lower (P < 0.05) than the treatment that received C or N and C (Table 2). These results agree with those reported by Weier et al. (1993), who while working on a soil with 6 mg kg-1 of NO3–N and a WFPS of 90%, found that cumulative DLs were 203, 360, and 303 g ha-1 d-1 when 0, 50, and 100 kg N ha-1 were added, respectively. However, when 180 kg of C ha-1 was added as glucose, cumulative DLs were 195, 6287, and 14227 g ha-1 d-1. Our results and those reported by Weier et al. (1993) indicate that C availability was the most important limiting factor controlling the denitrification process, even in soils with low NO3–N concentration. Myrold and Tiedje (1985), reported that C availability increases denitrification capacity by increasing microbial growth, and suggested that denitrifiers compete as effectively for C as the other heterotrophs. Denitrification rates of treatments that received C were greater than those observed in the field at the 19 d and the 37 d after PL for similar soil water content, and indicate that C availability severely limited the denitrification process under field conditions. Soil NO3–N content in the treatments with and without N for the 117 d after planting were similar (4.4 mg kg-1 of NO3–N) and considerably lower than that observed for the 17 d after planting (Fig. 2). Therefore, the DR of the treatment that received N and C was significantly greater (P < 0.05) than those that received N or C only, indicating that N and C availability limited the denitrification process.


View this table:
[in this window]
[in a new window]
  		Table 2. Analysis of variance of denitrification rate during 1-d incubation at an ambient temperature as affected by the N rate (main treatment) and by addition of the soluble N and C (subtreatments).

 

   CONCLUSION
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS AND DISCUSSION
 CONCLUSION
REFERENCES
 
Soil water content appeared to be the principal factor limiting DLs in this soil under NT. When N was applied at planting, cumulative DLs were greater than those observed for fertilization at the V6. On average, 5.5 and 2.6% of the N applied was lost from the 70 and 210 kg N ha-1, respectively, when N was applied at PL. However, 1.0 and 0.4% of the N applied was lost from the 70 and 210 kg N ha-1, respectively, when N was applied at theV6 stage. In both growing seasons, cumulative DL between planting and the V6 was increased by increasing the N rate, indicating that N availability limited denitrification process. The results also showed that the amount of C susceptible to mineralization under anaerobic conditions appeared as a factor limiting the denitrification process in this soil under NT.


   ACKNOWLEDGMENTS
 
This work was supported by the projects PICT-90 08-00000-00089 of the National Agency of Scientific and Technological Promotion, 15/A107 of the FCA-UNMP and by resources of the Agricultural Experimental Station INTA of Balcarce. The authors express their deepest gratitude to Dr. Miguel L. Cabrera by the review of the manuscript.

Received for publication July 10, 2000.


   REFERENCES
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS AND DISCUSSION
 CONCLUSION
 REFERENCES
 




This article has been cited by other articles:


Home page
 Agron. J.Home page
P. A. Barbieri, H. E. Echeverria, H. R. Sainz Rozas, and F. H. Andrade
Nitrogen Use Efficiency in Maize as Affected by Nitrogen Availability and Row Spacing
Agron. J., June 23, 2008; 100(4): 1094 - 1100.
[Abstract] [Full Text] [PDF]

Home page
 Agron. J.Home page
P. A. Barbieri, H. E. Echeverria, and H. R. Sainz Rozas
Presidedress Soil Nitrogen Test for No-Tillage Maize at Different Row Spacing
Agron. J., June 23, 2008; 100(4): 1101 - 1105.
[Abstract] [Full Text] [PDF]

Home page
 J. Environ. Qual.Home page
H. S. Steinbach and R. Alvarez
Changes in soil organic carbon contents and nitrous oxide emissions after introduction of no-till in Pampean agroecosystems.
J. Environ. Qual., January 1, 2006; 35(1): 3 - 13.
[Abstract] [Full Text] [PDF]

Home page
 Agron. J.Home page
H. R. S. Rozas, H. E. Echeverria, and P. A. Barbieri
Nitrogen Balance as Affected by Application Time and Nitrogen Fertilizer Rate in Irrigated No-Tillage Maize
Agron. J., November 1, 2004; 96(6): 1622 - 1631.
[Abstract] [Full Text] [PDF]

This Article
Right arrow Abstract Freely available
Right arrow Figures Only
Right arrow Full Text (PDF) Free
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Similar articles in this journal
Right arrow Similar articles in ISI Web of Science
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrow reprints & permissions
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via ISI Web of Science (11)
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Rozas, H. R. S.
Right arrow Articles by Picone, L. I.
Right arrow Search for Related Content
PubMed
Right arrow Articles by Rozas, H. R. S.
Right arrow Articles by Picone, L. I.
Agricola
Right arrow Articles by Rozas, H. R. S.
Right arrow Articles by Picone, L. I.
Related Collections
Right arrow Other Soil Management
Right arrow Tillage
Right arrow Soil Analysis

HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
The SCI Journals Agronomy Journal Crop Science
Journal of Natural Resources
and Life Sciences Education		 Vadose Zone Journal
Journal of Plant Registrations Journal of
Environmental Quality		 The Plant Genome