Agronomy Journal Grow Your Career With ASA
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 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 Web of Science (14)
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Sainju, U. M.
Right arrow Articles by Singh, B. P.
Right arrow Search for Related Content
PubMed
Right arrow Articles by Sainju, U. M.
Right arrow Articles by Singh, B. P.
Agricola
Right arrow Articles by Sainju, U. M.
Right arrow Articles by Singh, B. P.
Related Collections
Right arrow Other Crop Management
Right arrow Maize
Right arrow Plant Nutrition
Right arrow Other Soil Management
Right arrow Tillage
Agronomy Journal 93:878-886 (2001)
© 2001 American Society of Agronomy

SOIL MANAGEMENT

Tillage, Cover Crop, and Kill-Planting Date Effects on Corn Yield and Soil Nitrogen

Upendra M. Sainju* and Bharat P. Singh

Agric. Res. Stn., Fort Valley State Univ., 1005 State University Drive, Fort Valley, GA 31030

* Corresponding author (sainjuu{at}mail.fvsu.edu)

Received for publication September 25, 2000.

   ABSTRACT
TOP
 ABSTRACT
INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 SUMMARY AND CONCLUSIONS
 REFERENCES
 
Tillage and spring kill date may affect cover crop N accumulation and subsequent N release to the soil, thereby influencing corn (Zea mays L.) N uptake and yield. We examined the influence of three tillage practices [no till (NT), chisel plowing (CP), and moldboard plowing (MP)], two cover crop management systems [hairy vetch (Vicia villosa Roth) vs. winter weeds], and two cover crop kill–corn planting dates [early (early April cover crop kill and mid to late April corn planting) vs. late (mid to late April cover crop kill and late April to early May corn planting)] on cover crop N accumulation, soil inorganic N, and silage corn N uptake and yield. An experiment was conducted on a Dothan sandy loam (fine-loamy, siliceous, thermic, Plinthic Paleudults) from 1997 to 1999 in central Georgia. Cover crop N accumulation was higher with late kill than with early kill (113 vs. 104 kg ha-1). Corn yield was higher with late planting in NT than in CP or MP (19.5 vs. 15.1–16.6 Mg ha-1) and higher in CP or MP with early planting than in MP with late planting (18.1–18.4 vs. 15.1 Mg ha-1). Similarly, corn N uptake was higher in NT with late planting than in CP or MP with early or late planting (217 vs. 133–171 kg ha-1). Soil inorganic N (0- to 30-cm depth) at corn planting was higher in CP than in NT (18.4–30.2 vs. 9.9–20.5 mg kg-1). Corn yield and N uptake in NT and N concentration and uptake in CP and MP can be increased by delaying cover crop kill by 2 wk, but corn yield in CP and MP can be maintained by killing cover crop early in the spring.

Abbreviations: CP, chisel plowing • MP, moldboard plowing • NT, no till


   INTRODUCTION
TOP
 ABSTRACT
 INTRODUCTION
MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 SUMMARY AND CONCLUSIONS
 REFERENCES
 
A LEGUME COVER CROP, such as hairy vetch, can supply most of the N required for maximum corn yield (McVay et al., 1989; Clark et al., 1994, 1995, 1997a; Decker et al., 1994). Because of its high N concentration and low C/N ratio, hairy vetch residue can decompose rapidly in the soil (Kuo et al., 1997) and allow for synchrony of N release from the residue with corn N demand (Stute and Posner, 1995). Hairy vetch increased corn yield similar to fertilizer N rates of 66 to 200 kg ha-1 (Sainju and Singh, 1997). In addition, hairy vetch can improve soil and water quality compared with bare fallow by reducing erosion; NO3 leaching during fall, winter, and spring; and increasing organic matter (Sainju and Singh, 1997). In central Georgia, hairy vetch is well adapted, producing tomato (Lycopersicon esculentum Mill.) yields similar to fertilizer rates of 90 to 180 kg N ha-1 (Sainju et al., 1999, 2000a) and increasing soil organic C and N levels similar to those increased by rye (Secale cereale L.) and crimson clover (Trifolium incarnatum L.) cover crops (Sainju et al., 2000b).

Nitrogen supplied by hairy vetch can be influenced by tillage and time of kill. Clark et al. (1994)(1995, 1997a, 1997b) reported that delaying the spring kill date of hairy vetch from 2 to 6 wk increased its biomass yield and N accumulation. As a result, delayed planting of corn following late kill also increased its yield and N uptake in the no-till (NT) system because more N was supplied and soil moisture conserved by the residue. Nitrogen released by vetch residue can be mineralized into NH4 and NO3 forms. As plants absorb N mostly in NO3 form, it is not known whether delayed kill of vetch also increases the level of NO3 in the soil compared with NH4. Because tillage can influence the degree of residue incorporated into the soil and subsequent N mineralization, the type of tillage may affect the synchrony of N release from the residue with corn N demand (Huntington et al., 1985; Wagger, 1989a; Power et al., 1991).

Although a late-killed hairy vetch cover crop followed by late-planted corn can increase N uptake and yield compared with an early kill–early planting system in NT (Clark et al., 1995), little is known about the effect of tillage on N release from late-killed vetch residue and on subsequent N uptake and yield of late-planted corn. In chisel plow (CP) and moldboard plow (MP) systems, increased incorporation of late-killed vetch residue into soil followed by late planting may not increase corn N uptake and yield. In the southern Piedmont, farmers are often reluctant to adopt NT practices because of concerns about effective weed control, increased pesticide use, and reduced water percolation or crop rooting in dense subsoil (Franzluebbers et al., 1999). As a result, secondary tillage to control weeds or paraplowing to improve deep water percolation or root growth in dense subsoil are common (Franzluebbers et al., 1999). These alternative tillage practices are often employed to reduce producers' risk of crop failure by altering soil environmental conditions. Therefore, information is needed about the effect of late-killed hairy vetch on corn N uptake and yield in tilled systems, particularly in the Southeast.

We hypothesize that tillage affects N release from an early or late-killed cover crop, consequent soil inorganic N, and subsequent N uptake and yield of early or late-planted corn. Our objectives were to determine the effects of tillage, cover crop species, and cover crop kill–corn planting dates on cover crop biomass yield and N accumulation, soil inorganic N concentration, and silage corn N uptake and yield.


   MATERIALS AND METHODS
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
RESULTS
 DISCUSSION
 SUMMARY AND CONCLUSIONS
 REFERENCES
 
The experiment was conducted from 1997 to 1999 at the Agricultural Research Station farm, Fort Valley State University, Fort Valley, GA. The soil was a Dothan sandy loam with a pH of 6.5 and sand, silt, and clay contents of 650, 250, and 100 g kg-1, respectively, at 0- to 30-cm depth. The clay content increased to 350 g kg-1 below 30 cm. At 0 to 30 cm, organic C was 8.8 g kg-1 and organic N was 620 mg kg-1. Previous crops (5 yr) were wheat (Triticum aestivum L.), soybean [Glycine max L. (Merr.)], and tomato. Every year, the experiment was conducted in the same plots. Temperature and rainfall data were collected from a weather station that was 20 m from the experimental site.

The description and dates of cultural practices used for early and late cover crop kill–corn planting dates are shown in Table 1. The CP and MP plots were tilled in October for cover crop planting and in April through May of the following year for cover crop incorporation and corn planting. After cover crop mowing and thorough drying of the residue in the field, plots were harrowed two to three times using a disc harrow until residues were broken into small pieces and soil particles loosened before plowing. Because residues were broken into small pieces by mowing and harrowing, most were uniformly spread throughout the plot even after CP and MP operations. The NT plots were left undisturbed except for drilling cover crop seed and planting corn.


View this table:
[in this window]
[in a new window]
  		Table 1. Dates of cultural practices used for early and late cover crop kill and silage corn planting.

 
Hairy vetch seed inoculated with Rhizobium leguminosarum (bv. viceae) was drilled at 28 kg ha-1 using a row spacing of 15 cm. No fertilizer, herbicide, or insecticide was applied. At two kill dates (Table 1), vetch was harvested from two 1-m2 areas within each plot and weighed in the field for biomass yield determination. A subsample ({approx}100 g) was collected for determination of dry matter yield and N concentration, and the rest was returned to the harvested area where it was spread uniformly by hand. In the plots without vetch, winter weeds, dominated by henbit (Lamium amplexicaule L.) and cut-leaf evening primrose (Oenolthea laciniate L.), were collected using the same procedure. Plants were oven-dried at 60°C, weighed, and ground to pass a 1-mm screen. After sampling, vetch and weeds were mowed with a rotary mower to break the plants into small pieces, killed by spraying 3.36 kg a.i. ha-1 glyphosate [N-(phosphonomethyl) glycine] in NT plots, and incorporated into the soil by harrowing in CP and MP plots. Residues were allowed to decompose in the soil for 13 to 16 d before P and K fertilization and corn planting.

The treatments consisted of three levels of tillage (NT, CP, and MP), two cover crop management systems (hairy vetch vs. winter weeds), and two cover crop kill–corn planting dates (early and late; Table 1). Chisel plowing consisted of harrowing to a depth of 10 to 15 cm, followed by chiseling to 20 to 25 cm and leveling with a S-tine harrow. Similarly, MP consisted of harrowing, followed by moldboard plowing to 20 to 25 cm and leveling. The experiment was arranged in a split split-plot design with kill–planting date as the main plot, tillage as the split plot, and cover crop as the split split-plot treatment. Each treatment had three replications. The split split-plot size was 21.6 by 7.2 m.

At two corn-planting dates, P {from triple superphosphate [Ca(H2PO4)2]} fertilizer and K [from muriate of potash (KCl)] fertilizer were broadcast at 67 and 84 kg ha-1, respectively, to all plots based on the soil test. Phosphorus and K fertilizer requirements for corn were similar in 1998 and 1999. The fertilizers were incorporated into the soil by plowing in CP and MP plots and left at the soil surface in NT plots. No N fertilizer was applied. Following tillage, silage corn (cv. McNair 508) was planted at 70000 seeds ha-1 in 8-row plots (0.9-m spacing). Within a day of planting, atrazine [6-chloro-N-ethyl-N'-(1-methylethyl)-1,3,5-triazine-2,4-diamine] and metolachlor [2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-1-methylethyl) acetamide] were applied at 1.5 and 1.3 kg a.i. ha-1, respectively, to control postemergence of weeds. Irrigation (equivalent to 25 mm of rain at a time using reel rain gun) was applied on 12 and 27 May, 15 June, and 18 July in 1998 and on 10 and 25 Apr. and 7 and 20 May in 1999 to prevent moisture stress.

In August of each year, two middle rows (40.0 by 1.8 m) of corn were hand-harvested from each plot for biomass yield determination. Six representative plants were weighed and chopped, and a known amount of subsample was collected in the field. The subsample was oven-dried at 60°C for 3 d, weighed again for dry matter yield determination, and ground to pass a 1-mm screen for N analysis. Soil samples at 0- to 30-cm depth were collected from all plots at 4 to 7 d before cover crop kill, at two corn-planting dates, and at harvest (Table 1). Soil samples were collected from a push tube (2.5 cm i.d.) from 15 places within the plot after removing visible plant residues and then composited, air-dried, and ground to pass a 2-mm sieve for inorganic N analysis.

Nitrogen concentration in the cover crop and corn samples was determined by the H2SO4–H2O2 method as described by Kuo et al. (1997). Nitrogen accumulation in cover crop and corn was determined by multiplying dry matter weight by N concentration. The NH4 and NO3 concentrations in the soil were determined by steam distillation (Mulvaney, 1996) after extracting with 2 M KCl. Inorganic N was determined as the sum of NH4 and NO3 concentrations.

Data for plant and soil parameters were analyzed using the MIXED procedure of SAS after testing for homogeneity of variance (Littell et al., 1996). Sources of variation included year, kill–planting date, tillage, cover crop, and their interactions. Means were separated by the least square means test when treatments and their interactions were significant. Statistical significance was evaluated at P <= 0.05.


   RESULTS
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
DISCUSSION
 SUMMARY AND CONCLUSIONS
 REFERENCES
 
Climate
Average monthly temperature increased in a similar pattern from April to August in 1998 and 1999 and ranged from 15.0°C in April to 25.5°C in August. Total monthly rainfall in June and July, however, was higher in 1999 than in 1998 and higher than the 41-yr average (Fig. 1). Total rainfall from April to August was also higher in 1999 than in 1998 but lower than the 41-yr average.



View larger version (23K):
[in this window]
[in a new window]
  		Fig. 1. Monthly total rainfall from April to August in 1998 and 1999 and the 41-yr average. The number inside the parenthesis indicates total rainfall from April to August. The hatch (->) indicates time of irrigation application for silage corn. Irrigation equivalent to 25 mm rain at a time was applied using a reel rain gun.

 
Cover Crop Biomass Yield and Nitrogen Accumulation
Significant difference in years and cover crop treatments occurred for cover crop biomass yield, N concentration, and N accumulation while kill date differed for N accumulation (Table 2). Interactions were significant for tillage x cover crop (biomass), year x cover crop, year x kill date x tillage x cover crop (biomass and N accumulation), and year x cover crop (N concentration).


View this table:
[in this window]
[in a new window]
  		Table 2. Analysis of variance for cover crop and silage corn biomass yield, N concentration, and N accumulation or uptake.

 
Cover crop biomass yield, N concentration, and N accumulation varied in 1998 and 1999 (Table 3). In 1998, hairy vetch biomass yield was significantly higher in NT with early kill (3.79 Mg ha-1) than in CP with early kill (2.97 Mg ha-1) or in MP with late kill (3.00 Mg ha-1). Vetch N accumulation was higher in NT with late kill (127 kg ha-1) than in CP with early kill (104 kg ha-1) or in MP with early or late kill (105 kg ha-1). In 1999, biomass was higher in MP with late kill (6.74 Mg ha-1) than in MP or NT with early kill (5.66–5.71 Mg ha-1) or in CP with late kill (5.92 Mg ha-1). Nitrogen accumulation did not differ between tillage and kill dates (234–257 kg ha-1).


View this table:
[in this window]
[in a new window]
  		Table 3. Effects of tillage, cover crop, and kill date on cover crop biomass yield, N concentration, and N accumulation in 1998 and 1999.

 
Averaged across years, vetch biomass yield (4.42–4.88 Mg ha-1) and N accumulation (169–189 kg ha-1) were similar between tillage and kill dates and were higher than weed biomass yield (1.13–1.87 Mg ha-1) and N accumulation (17–39 kg ha-1), respectively (Table 3). Averaged across years and kill dates, vetch biomass was not affected by tillage, but weed biomass was higher in CP or MP than in NT (Fig. 2). Averaged across treatments, cover crop biomass was 65% higher, N concentration 13% higher, and N accumulation 101% higher in 1999 than in 1998 (Table 3). Similarly, biomass was 187% higher, N concentration 90% higher, and N accumulation 458% higher in vetch than in weeds. Cover crop N accumulation was also 9% higher with late kill than with early kill.



View larger version (15K):
[in this window]
[in a new window]
  		Fig. 2. Effect of tillage on biomass yield of hairy vetch and winter weeds. NT, no till; CP, chisel plowing; and MP, moldboard plowing. Bars with the same letter at the top are not significantly different by the least square means test (P <= 0.05).

 
Silage Corn Yield and Nitrogen Uptake
Silage corn yield varied significantly for year and N concentration, and N uptake varied significantly for year, planting date, and cover crop (Table 2). Interactions were significant for year x planting date, planting date x tillage, planting date x cover crop, year x planting date x cover crop (corn yield and N uptake), year x planting date (N concentration), and year x planting date x tillage x cover crop (N uptake).

Silage corn yield, N concentration, and N uptake varied between years. In 1998, corn yield, averaged across tillage, was higher with early than with late planting in both vetch and weed covers, but N uptake was higher in vetch with late planting than in weeds with early planting (Fig. 3A and 3C). In 1999, corn yield was higher in vetch with early planting or in weeds with late planting than in vetch with late planting or in weeds with early planting (Fig. 3B). Nitrogen uptake was higher in vetch with early planting or in weeds with late planting than in weeds with early planting (Fig. 3D).



View larger version (28K):
[in this window]
[in a new window]
  		Fig. 3. Effects of cover crop kill–corn planting date (early and late) and cover crop species on (A and B) silage corn yield and (C and D) N uptake in 1998 and 1999. The cover crop kill and corn planting dates are shown in Table 1. Within a year, bars with the same letter at the top are not significantly different by the least square means test (P <= 0.05).

 
Averaged across years and cover crops, corn yield was higher in NT with late planting than in CP or MP with late planting and higher in CP or MP with early planting than in MP with late planting (Fig. 4A). Nitrogen uptake was higher in NT with late planting than in NT with early planting or in CP or MP with early or late planting and higher in CP with late planting than in NT with early planting (Fig. 4B). Averaged across tillage and cover crops, yield was higher with early than with late planting in 1998, but N concentration and N uptake were higher with late than with early planting in 1998 and 1999 (Table 4). Averaged across treatments, yield was 61% higher and N uptake 37% higher, but N concentration was 25% lower in 1999 than in 1998. Similarly, N concentration was 17% higher and N uptake 18% higher with vetch than with weeds. Nitrogen concentration was also 39% higher and N uptake 24% higher with late than with early planting.



View larger version (22K):
[in this window]
[in a new window]
  		Fig. 4. Effects of cover crop kill–corn planting date (early and late) and tillage on (A) silage corn yield and (B) N uptake. NT, no till; CP, chisel plowing; and MP, moldboard plowing. The cover crop kill and corn planting dates are shown in Table 1. Bars with the same letter at the top are not significantly different by the least square means test (P <= 0.05).

 

View this table:
[in this window]
[in a new window]
  		Table 4. Effects of tillage, cover crop, and planting date on silage corn yield, N concentration, and N uptake in 1998 and 1999.

 
Soil Inorganic Nitrogen
Soil NH4, NO3, and inorganic N concentrations at 4 to 7 d before cover crop kill were not significant for main treatments and interactions. The NH4 concentration ranged from 1.3 to 2.5 mg kg-1, NO3 from 4.5 to 6.0 mg kg-1, and inorganic N from 5.8 to 8.5 mg kg-1. At corn planting, NH4 concentration was significantly different for year and cover crop, and NO3 and inorganic N were significantly different for all main treatments (Table 5). Interactions were significant for year x planting date x cover crop for NH4 and year x planting date, year x planting date x tillage, year x cover crop, and tillage x cover crop for NO3 and inorganic N at planting. At corn harvest, NH4, NO3, and inorganic N were different for year.


View this table:
[in this window]
[in a new window]
  		Table 5. Analysis of variance for soil inorganic N at silage corn planting (Plant.) and harvest (Harv.).

 
At corn planting, soil NH4, NO3, and inorganic N concentrations varied between years. In 1998, NH4 concentration, averaged across tillage, was not influenced by cover crop and planting date (3.3 to 4.3 mg kg-1), but in 1999, NH4 was higher in vetch with early or late planting than in weeds with early planting (4.9–5.2 mg kg-1 vs. 3.4 mg kg-1). Because NO3 and inorganic N concentrations varied similarly for the treatments (Table 5), only the results for inorganic N will be presented. In 1998, inorganic N, averaged across cover crops, was higher in CP with early planting than in CP with late planting, MP with early planting, or NT with early or late planting and higher in MP with late planting than in MP with early planting or NT with late planting (Fig. 5A). In 1999, inorganic N was higher in CP with late planting than in CP or MP with early planting or in NT with early or late planting and higher in MP with late planting than in NT with early planting (Fig. 5B).



View larger version (20K):
[in this window]
[in a new window]
  		Fig. 5. Effects of cover crop kill–corn planting date (early and late) and tillage on soil inorganic N concentration in (A) 1998 and (B) 1999. NT, no till; CP, chisel plowing; and MP, moldboard plowing. The cover crop kill and corn planting dates are shown in Table 1. Within a year, bars with the same letter at the top are not significantly different by the least square means test (P <= 0.05).

 
Averaged across tillage and cover crops, soil inorganic N at corn planting was not influenced by planting date in 1998 but was higher with late than with early planting in 1999 (Table 6). Averaged across planting dates and tillage, inorganic N was higher with vetch than with weeds in 1998 and 1999. Averaged across years and planting dates, inorganic N was higher in CP or MP with vetch than in NT with vetch or CP, MP, or NT with weeds and higher in NT with vetch than in CP, MP, or NT with weeds (Fig. 6). Averaged across treatments, NH4 was 17% higher and inorganic N 71% higher in 1999 than in 1998 (Table 6). Similarly, NH4 was 24% higher and inorganic N 123% higher with vetch than with weeds. Inorganic N was also 40 and 25% higher in CP and MP, respectively, than in NT and 10% higher with late than with early planting. At corn harvest, NH4 was 28% (3.7 mg kg-1) higher and inorganic N 82% (12.0 mg kg-1) higher in 1999 than in 1998. The NH4 concentration accounted for 23 and 35% of inorganic N at corn planting and harvest, respectively.


View this table:
[in this window]
[in a new window]
  		Table 6. Effects of tillage, cover crop, and planting date on soil inorganic N at silage corn planting in 1998 and 1999.

 


View larger version (18K):
[in this window]
[in a new window]
  		Fig. 6. Effects of tillage and cover crop on soil inorganic N concentration. NT, no till; CP, chisel plowing; and MP, moldboard plowing. Bars with the same letter at the top are not significantly different by the least square means test (P <= 0.05).

 

   DISCUSSION
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
SUMMARY AND CONCLUSIONS
 REFERENCES
 
Although tillage interacted with cover crop treatment and kill date to influence cover crop biomass yield and N accumulation, the higher N accumulation with late than with early kill, regardless of tillage (Table 3), resulted from increased biomass yield and/or N concentration in the cover crops when they were allowed to grow more by 2 wk in the spring. Similar increases in hairy vetch N accumulation with late vs. early spring kill were reported by several researchers (Wagger, 1989b; Sullivan et al., 1991; Clark et al., 1995; Vaughn and Evanylo, 1998). Both biomass yield and N concentration were higher with late than with early kill although not significantly different (Table 3). This is because growth of cover crops, such as hairy vetch, is more rapid in the spring than in the late fall or winter due to increased temperature, thereby resulting in increased biomass production and N accumulation (Clark et al., 1995; Sainju et al., 1998). Average monthly temperature increased from 9.5°C in December 1997 to 20.6°C in May 1998 and from 8.9°C in December 1998 to 21.8°C in May 1999. Clark et al. (1995) observed that from early April to mid-May, hairy vetch biomass increased from 2.8 to 4.6 Mg ha-1, and N accumulation increased from 96 to 149 kg ha-1.

The C/N ratio of cover crop residue can influence soil N mineralization and N availability to subsequent crops (Allison, 1966; Wagger, 1989b; Kuo et al., 1996). While C concentration of cover crops in this experiment was not measured because of close correlation between C/N ratio and N concentration (Kuo et al., 1996), several researchers (Wagger 1989b; Clark et al., 1994; Vaughn and Evanylo, 1998) have observed that C/N ratio in hairy vetch residue did not alter significantly within a 4-wk period of early and late kill because both C and N concentrations did not differ between kill dates. They observed that C/N ratio of early or late-killed hairy vetch residue was well below 25:1, a limit that determines N mineralization or immobilization from plant residue (Allison, 1966; Wagger, 1989b; Vigil and Kissel, 1991). Because N concentration of cover crops was not influenced by kill date (Table 3), it was assumed that C/N ratio did not significantly alter between early and late kill dates.

The effects of tillage, cover crop, and kill-planting date on soil NH4 concentration were minimal (Table 6), probably because N mineralized from cover crop residue is readily converted into NO3. In contrast, NO3 and inorganic N concentrations at corn planting increased with hairy vetch, plowing, and late kill–planting date compared with winter weeds, NT, and early kill–planting date, respectively. While late kill resulted in more cover crop N accumulation than early kill, plowing incorporated cover crop residue, increasing N mineralization rate (Wilson and Hargrove, 1986; Brown et al., 1993; Schomberg et al., 1994; Vaughn and Evanylo, 1998). As a result, NO3 and inorganic N were higher in CP or MP with late corn planting than in NT with early or late planting (Table 6 and Fig. 5). Residue accumulated at the soil surface in NT probably acted as a mulch and influenced soil moisture conservation more than N mineralization. Nonsignificant effects of treatments on NH4, NO3, and inorganic N concentrations at harvest (Table 5) indicated that soil mineral N is either taken up by corn, immobilized in soil microbial biomass, or lost through leaching, volatilization, or denitrification.

The increased availability of soil inorganic N at corn planting with CP or MP compared with NT did not improve silage corn yield and N uptake because yield and N uptake were not influenced by tillage (Table 2). Increased corn N concentration and uptake and soil inorganic N following delayed cover crop kill and corn planting, regardless of tillage (Tables 4 and 6), however, may have resulted from increased synchronization of cover crop N release with corn N demand. The improved corn yield and N uptake in NT with late planting (Fig. 4) may have resulted from increased soil moisture conservation due to mulch effect of the residue accumulated at the soil surface, followed by increasing N mineralization rate and increased cover crop N accumulation following late killing, as was observed by Clark et al. (1994)(1995, 1997a, 1997b). They found that delaying the kill of hairy vetch by 2 to 6 wk from late April to mid-May increased its biomass production and N accumulation, soil moisture after kill, and subsequent corn yield and N uptake compared with early kill in early April in the NT system. They also observed that although late kill decreased soil moisture at planting, it did not influence corn growth. Increased residue cover at the soil surface following late kill, however, increased soil moisture later in the season and improved corn yield. Increased corn yield with early vs. late planting in CP or MP (Fig. 4A) suggests that legume cover crops may be killed and incorporated early, followed by early planting in the spring. Delaying (by 2 wk) kill and incorporation may, however, improve corn N concentration and uptake (Table 4 and Fig. 4B).

The higher corn yield and N uptake in 1999 than in 1998 may have resulted from increased soil moisture and N mineralization due to increased rainfall and the amount of N supplied by cover crop residue. The June and July rainfall, critical for corn growth, and total rainfall from April to August were higher in 1999 than in 1998 (Fig. 1). Although soil moisture stress to corn was prevented by using irrigation equivalent to 25 mm of rain once or twice a month during dry periods (Fig. 1), moisture stress may not have been completely prevented during May to August 1998. In contrast, higher rainfall in June and July probably decreased moisture stress and increased soil N mineralization and availability (Table 6), thereby increasing corn yield and N uptake in 1999 compared with 1998 (Table 4). Soil moisture content can influence N mineralization and availability (Stanford and Epstein, 1974; Schomberg et al., 1994; Vaughn and Evanylo, 1998) and subsequent corn growth and N uptake (Clark et al., 1995, 1997b; Kuo et al., 1996). Increased soil inorganic N in 1999 compared with 1998 also may have resulted from a higher amount of N supplied by cover crop residue (Table 3) and from mineralization of N from the previous year's cover crop and corn residues. Because soil NH4, NO3, and inorganic N before cover crop kill were not significantly different between treatments (P <= 0.05), the residual effect of cover crop N from 1998 to 1999 was considered minimal. Because hairy vetch residue decomposes rapidly in the soil, the inorganic N at corn harvest following cover crop incorporation remained at the same level as with the control without a cover crop (Kuo et al., 1997).


   SUMMARY AND CONCLUSIONS
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 SUMMARY AND CONCLUSIONS
REFERENCES
 
Delayed kill of a hairy vetch cover crop by 2 wk in the spring significantly increased N accumulation. Incorporation of such residue into the soil in CP or MP increased soil inorganic N compared with NT by increasing N mineralization from the residue but did not increase silage corn yield. Delayed corn planting following late kill, however, increased soil mineral N and corn N concentration and uptake, regardless of tillage, probably due to better synchrony of cover crop N release with corn N demand. Increased soil moisture conservation by the residue, followed by increasing N mineralization rate, may have increased corn yield and N uptake in NT with late planting than in CP or MP with late planting. Corn yield was also higher in CP or MP with early planting than in MP with late planting. Producers can increase corn silage yield and N uptake in the NT production system by delaying the cover crop kill by at least 2 wk, followed by late planting. In CP and MP systems, cover crops can be killed early, followed by early planting in the spring to sustain corn yield, but kill–planting date can be delayed by 2 wk to improve corn quality by increasing N concentration and uptake. The economics of late cover crop kill compared with N fertilization in corn yield and N uptake needs to be examined, but with increasing energy cost for N fertilizer production, late kill of legume cover crops to supply N, increase corn N concentration and uptake, and sustain corn yields may be justified.


   REFERENCES
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 SUMMARY AND CONCLUSIONS
 REFERENCES
 




This article has been cited by other articles:


Home page
 Soil Sci.Home page
S. Senthilkumar, A. N. Kravchenko, and G. P. Robertson
Topography Influences Management System Effects on Total Soil Carbon and Nitrogen
Soil Sci. Soc. Am. J., October 21, 2009; 73(6): 2059 - 2067.
[Abstract] [Full Text] [PDF]

Home page
 Agron. J.Home page
L. Zotarelli, L. Avila, J. M. S. Scholberg, and B. J. R. Alves
Benefits of Vetch and Rye Cover Crops to Sweet Corn under No-Tillage
Agron. J., February 4, 2009; 101(2): 252 - 260.
[Abstract] [Full Text] [PDF]

Home page
 Agron. J.Home page
B. Kramberger, B. Lukac, D. Gruskovnjak, and A. Gselman
Effects of Italian Ryegrass and Date of Plow-In on Soil Mineral Nitrogen and Sugarbeet Yield and Quality
Agron. J., August 11, 2008; 100(5): 1332 - 1338.
[Abstract] [Full Text] [PDF]

Home page
 Agron. J.Home page
M. A. Cavigelli, J. R. Teasdale, and A. E. Conklin
Long-Term Agronomic Performance of Organic and Conventional Field Crops in the Mid-Atlantic Region
Agron. J., May 7, 2008; 100(3): 785 - 794.
[Abstract] [Full Text] [PDF]

Home page
 Agron. J.Home page
M. Al-Kaisi and D. Kwaw-Mensah
Effect of Tillage and Nitrogen Rate on Corn Yield and Nitrogen and Phosphorus Uptake in a Corn-Soybean Rotation
Agron. J., October 15, 2007; 99(6): 1548 - 1558.
[Abstract] [Full Text] [PDF]

Home page
 Agron. J.Home page
U. M. Sainju, B. P. Singh, W. F. Whitehead, and S. Wang
Accumulation and Crop Uptake of Soil Mineral Nitrogen as Influenced by Tillage, Cover Crops, and Nitrogen Fertilization
Agron. J., April 4, 2007; 99(3): 682 - 691.
[Abstract] [Full Text] [PDF]

Home page
 Agron. J.Home page
C. M. Cherr, J. M. S. Scholberg, and R. McSorley
Green Manure as Nitrogen Source for Sweet Corn in a Warm-Temperate Environment
Agron. J., August 3, 2006; 98(5): 1173 - 1180.
[Abstract] [Full Text] [PDF]

Home page
 Agron. J.Home page
D. Kwaw-Mensah and M. Al-Kaisi
Tillage and Nitrogen Source and Rate Effects on Corn Response in Corn-Soybean Rotation
Agron. J., April 11, 2006; 98(3): 507 - 513.
[Abstract] [Full Text] [PDF]

Home page
 Agron. J.Home page
C. M. Cherr, J. M. S. Scholberg, and R. McSorley
Green Manure Approaches to Crop Production: A Synthesis
Agron. J., February 7, 2006; 98(2): 302 - 319.
[Abstract] [Full Text] [PDF]

Home page
 Crop Sci.Home page
F. E. Miguez and G. A. Bollero
Review of Corn Yield Response under Winter Cover Cropping Systems Using Meta-Analytic Methods
Crop Sci., September 23, 2005; 45(6): 2318 - 2329.
[Abstract] [Full Text] [PDF]

Home page
 Agron. J.Home page
M. A. Licht and M. Al-Kaisi
Corn Response, Nitrogen Uptake, and Water Use in Strip-Tillage Compared with No-Tillage and Chisel Plow
Agron. J., April 27, 2005; 97(3): 705 - 710.
[Abstract] [Full Text] [PDF]

Home page
 Agron. J.Home page
M. Al-Kaisi and M. A. Licht
Effect of Strip Tillage on Corn Nitrogen Uptake and Residual Soil Nitrate Accumulation Compared with No-Tillage and Chisel Plow
Agron. J., July 1, 2004; 96(4): 1164 - 1171.
[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 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 Web of Science (14)
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Sainju, U. M.
Right arrow Articles by Singh, B. P.
Right arrow Search for Related Content
PubMed
Right arrow Articles by Sainju, U. M.
Right arrow Articles by Singh, B. P.
Agricola
Right arrow Articles by Sainju, U. M.
Right arrow Articles by Singh, B. P.
Related Collections
Right arrow Other Crop Management
Right arrow Maize
Right arrow Plant Nutrition
Right arrow Other Soil Management
Right arrow Tillage

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