Agronomy Journal Grow Your Career With ASA
HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
QUICK SEARCH:   [advanced]


     

Published online 5 September 2006
Published in Agron J 98:1290-1297 (2006)
DOI: 10.2134/agronj2006.0002
© 2006 American Society of Agronomy
677 S. Segoe Rd., Madison, WI 53711 USA
This Article
Right arrow Abstract Freely available
Right arrow Figures Only
Right arrow Full Text (PDF)
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 Google Scholar
Google Scholar
Right arrow Articles by Vasilakoglou, I.
Right arrow Articles by Lithourgidis, A.
Right arrow Search for Related Content
PubMed
Right arrow Articles by Vasilakoglou, I.
Right arrow Articles by Lithourgidis, A.
Agricola
Right arrow Articles by Vasilakoglou, I.
Right arrow Articles by Lithourgidis, A.
Related Collections
Right arrow Tillage
Right arrow Weed Management
Right arrow Allelopathy
Right arrow Cover Crops
Right arrow Cotton

Production Papers

Winter Cereal Cover Crop Mulches and Inter-Row Cultivation Effects on Cotton Development and Grass Weed Suppression

I. Vasilakogloua,*, K. Dhimab, I. Eleftherohorinosc and A. Lithourgidisd

a Weed Science Lab, Technol. & Educ. Inst. of Larissa, 411 10 Larissa, Greece
b Agron. Lab., Technol. & Educ. Inst. of Thessaloniki, 541 01 Thessaloniki, Greece
c Agron. Lab. Aristotle Univ. of Thessaloniki, 541 24 Thessaloniki, Greece
d Agron. Dep., Univ. Farm, Aristotle Univ. of Thessaloniki, 570 01 Thermi, Greece

* Corresponding author (vasilakoglou{at}teilar.gr)

Received for publication January 3, 2006.

   ABSTRACT
TOP
 ABSTRACT
INTRODUCTION
 MATERIALS AND METHODS
 RESULTS AND DISCUSSION
 CONCLUSIONS
 REFERENCES
 
A field experiment was conducted under Mediterranean conditions to study the effects of two barley (Hordeum vulgare L.), six triticale (X Triticosecale Wittmack) cultivars and three rye (Secale cereale L.) populations, used as cover crop mulches on the development of barnyardgrass [Echinochloa crus-galli (L.)], bristly foxtail [Setaria verticillata (L.) P. Beauv.], large crabgrass [Digitaria sanguinalis (L.) P. Scop.], and cotton (Gossypium hirsutum L.). Cotton was grown with cereal mulches alone or in treatment combinations that included inter-row cultivation, herbicide (quizalofop) application, or both. Three weeks after cotton planting, barnyardgrass, bristly foxtail, and large crabgrass emergence in mulched treatments was 28 to 69%, 33 to 57%, and 35 to 83% lower, respectively, than emergence in mulch-free treatments. On the contrary, cotton emergence was not significantly affected by any of the cover crop mulches. Shoot number and fresh weight of the three weeds were in most cases decreased in cereal-mulched treatments and were less in inter-row cultivated treatments compared to those in uncultivated treatments. Cotton lint yields in cereal mulched-inter-row-cultivated treatments were 28 to 84% greater than that in the corresponding mulch-free treatments. However, cotton produced more lint yield when the three grasses had been controlled by quizalofop. The results of this study indicated that some winter cereals have the ability to suppress germination of annual grass weeds and in combination with inter-row cultivation could increase cotton yield. However, herbicide usage is essential to maximize cotton yield and consequently to satisfy cotton producers.

Abbreviations: CLY, cotton lint yield • POCB, percentage of open cotton bolls • TNCB, total number of cotton bolls • WAP, weeks after planting


   INTRODUCTION
TOP
 ABSTRACT
 INTRODUCTION
MATERIALS AND METHODS
 RESULTS AND DISCUSSION
 CONCLUSIONS
 REFERENCES
 
COVER CROPS have increased yield of several crops including soybean [Glycine max (L.) Merr.], sugar beet (Beta vulgaris L.), corn (Zea mays L.), and green bean (Phaseolus vulgaris L.) (Brandsæter and Netland, 1999; Dhima et al., 2006; Haramoto and Gallandt, 2005; Kobayashi et al., 2004; Moore et al., 1994; Nagabhushana et al., 2001; Petersen and Rover, 2005; Reddy, 2001, 2003). Cover crops can improve soil water retention, increase soil organic matter, and reduce soil erosion (Khanh et al., 2005; Nyakatawa et al., 2001). The ability of cover crops to release phytotoxic (allelopathic compounds) chemicals in the environment and to create an unfavorable environment for weed germination and establishment could explain the cover crop potential to suppress weeds (Khanh et al., 2005). In particular, several researchers (Dhima et al., 2006; Kobayashi et al., 2004; Moore et al., 1994; Reddy, 2001, 2003) reported that rye, barley and triticale have the ability to release phytotoxic substances in the environment and to suppress weed germination and establishment after their use as cover crop mulches in corn and soybean. Therefore, these three species are increasingly adopted for their use as cover crops in several cropping systems (Dhima et al., 2006). However, the crop suppressive ability is strongly affected by environmental conditions and cultivar (Burgos et al., 1999; Kobayashi, 2004).

Cotton is one of the most important and profitable crops in Greece and cotton hectacreage during 2003 to 2005 averaged 360 000 ha, 45% of the total cultivated and irrigated area in Greece (NSSG, 2005). Growth of cotton is significantly affected by weed competition and yield reduction depends on weed species, density, time of weed emergence, and removal time of weeds (Papamichail et al., 2002). According to the Cotton Board of Greece, weed control in 96% of the Greek cotton area is based on the application of two to four different herbicides together with hand-weeding and inter-row mechanical cultivation. Although effective weed control can be achieved by an integration of several techniques, the economic costs ({approx}10% of the total economic profit) and environmental impact of herbicide use and tillage are being scrutinized. Cover crop mulches are among the required practices by the European Union for soil improvement. However, there is limited published data on the effect of cover crop mulches on weed emergence and growth, as well as cotton productivity under Mediterranean conditions either alone or in combination with tillage and herbicide use. The objectives of this research were to study, under Mediterranean field conditions, the effects of three rye populations, six triticale, and two barley cultivars used as crop mulches, alone or in combination with inter-row mechanical cultivation and herbicide application 4 wk after planting (WAP): i) on cotton growth and yield, and ii) on emergence and growth of three of the most important annual grass weeds (barnyardgrass, bristly foxtail, and large crabgrass) in Greek cotton fields.


   MATERIALS AND METHODS
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
RESULTS AND DISCUSSION
 CONCLUSIONS
 REFERENCES
 
Winter Cereal Agronomic Practices
A field experiment was conducted and repeated during the 2002 to 2003 and 2003 to 2004 growing seasons at the University Farm of Thessaloniki in northern Greece (22°59'6.17'' E, 40°32'9.32'' N). Experiments were established on a calcareous loam soil (Typic Xerorthent) whose physicochemical characteristics were: silt, 480 g kg–1; clay, 270 g kg–1; sand, 250 g kg–1; organic matter, 15 g kg–1; and pH, (1:2 H2O) 8.3.

In all experimental plots, N was applied as ammonium sulfate [(NH4)2SO4] and P as super phosphate [Ca(H2PO4)2] at 50 and 66 kg ha–1, respectively. Fertilizers were incorporated into the soil before planting winter cereals. Three rye populations originating from Albania, Greece, and Germany; six triticale (‘Niovi’, ‘Thisvi’, ‘Vronti’, ‘Vrito’, ‘Artemis’, and ‘Catria’), and two barley (‘Athinaida’ and ‘Thessaloniki’) cultivars from Greece were planted at a seed rate of 160 kg ha–1 on 18 Nov. 2002 and 29 Nov. 2003. Plots were 10 by 7 m and separated by a 2-m wide alley.

During the cereal-growing period, herbicides were not used on the winter cereals because of their low weed infestation. However, in the mulch-free treatments, 0.6 kg ha–1 of paraquat (1,1'-dimethyl-4,4'-bipyridinium) was applied postemergence about 3 wk before winter cereal incorporation. This application reduced weed residues and minimized possible allelopathic effects in this treatment. Other cultural practices were performed according to recommended production practices for the area.

Cotton Agronomic Practices
The winter cereals were incorporated by rotovator (width 145 cm, Model 4658001, Pythagoras Co., Thessaloniki, Greece) into the soil (8–10-cm depth) at the early to late boot growth stage (Feekes growth stage [FGS] 9–10) (Large, 1954). The incorporation dates were 10 Apr. 2003 and 16 Apr. 2004. Ten days later, 12 g m–2 barnyardgrass (approximately 2500 seeds m–2), 6 g m–2 bristly foxtail (approximately 4000 seeds m–2), and 5 g m–2 large crabgrass (approximately 6000 seeds m–2) were dispersed uniformly across the entire treatment area. The seeds of the three grasses, which were harvested from a nearby area during the previous year of each experiment, were uniformly dispersed in the experimental area by hand. The germinability of these seeds, evaluated before planting in a growth chamber experiment, was 26% for barnyardgrass, 14% for bristly foxtail, and 9% for large crabgrass. After dispersal, the weed seeds were incorporated into the soil (5-cm depth) with a rotovator. Generally, the grass weed density achieved was slightly greater than that typically observed in Greek cotton fields. This was done to study in-field allelopathic potential of winter cereal mulches under the possibly highest grass weed infestation.

Two days before cotton planting (simultaneously with the weed–seed incorporation), 120 kg N ha–1 as ammonium sulfate and 60 kg P ha–1 as super phosphate were incorporated into the soil of all experimental plots. Cotton cultivar Vered 171 was planted in 90-cm rows at an approximate density of 185 000 seed ha–1. The planting dates were 22 Apr. 2003 and 28 Apr. 2004. Carbofuran (2,3-dihydro-2, 2-dimethylbenzofuran-7-ylmethylcarbamate) was applied at 1.2 kg ha–1 at cotton planting for general insect management. Deltamethrin [(1R,3R)-3(2,2-dibromovinyl)-2,2-dimethylcyclopropanecarboxylic acid (S)-alpha-cyano-3-phenoxy-benzyl ester] was applied at 0.015 kg ha–1 during the season for cotton bollworm (Helicoverpa armigera Hübner) control. Irrigation and other common cultural practices were imposed as needed during the growing season. Mean monthly temperature and rainfall data recorded near the experimental area are given in Fig. 1 .


Figure 1
View larger version (16K):
[in this window]
[in a new window]
  		Fig. 1. Total monthly rainfall and mean monthly temperature during the experiment.

 
A split-split-plot arrangement of treatments was employed in a randomized complete block design with four replicates. Main plots consisted of the 11 winter cereals and a cover crop mulch-free control with plot size of 10 by 7 m. Each main plot consisted of eight rows of cotton and was divided into two subplots of four rows each. One subplot was mechanically cultivated 4 WAP and the other was not cultivated. All subplots were separated by a 1-m wide alley. Each subplot was subdivided into two 4.5- by 3-m areas, one that remained herbicide-free and one that received a grass herbicide treatment. Grass weed control in these sub-subplots was achieved by quizalofop {(±)-2-[4-[(6-chloro-2-quinoxalinyl)oxy]phenoxy]propanoic acid} applied postemergence 4 WAP at 0.075 kg ha–1. Also, broadleaf weeds in all plots were removed by hand during both growing seasons.

Cotton stand and weed density were counted in a 4.0- by 0.9-m area in the central inter-row of each plot at 3 WAP. Biomass (fresh weight) and number of shoots of barnyardgrass, bristly foxtail, and large crabgrass plants were determined by hand removal of these weeds in a 1.1- by 0.9-m area at 13 (late July) and 16 (mid-August) WAP. These dates were chosen because late in July the grass weeds had the greater biomass and the critical period of competition between cotton and weeds (4–12 WAP) had been completed (Buchanan and Burns, 1970).

At harvest, total number of cotton bolls (TNCB) and the number of open cotton bolls per meter of the two crop rows were determined, and then percentage of open cotton bolls (POCB) was calculated by multiplying the ratio open bolls/total bolls by 100. Both TNCB and POCB are cotton yield components, which are strongly correlated with the final cotton yield. Cotton seed yield was also determined by hand-harvesting the open bolls of cotton plants of the two 4.5-m-long center rows of each sub-subplot at late October (first harvest) and early November (second harvest) of both growing seasons. Cotton was harvested twice because this is the typical practice in Greek fields where cotton is cultivated. Furthermore, percentage cotton lint (ginning percentage) was determined and the cotton lint yield (CLY) was evaluated by multiplying the cotton seed yield by a ginning percentage of 40%.

Statistical Analysis
A combined-across growing season analysis of variance (ANOVA) was performed for all measured parameters using MSTAT (MSTAT-C, 1988). In particular, for the emergence of cotton and the three grass weeds a factorial approach (growing season x cover crop mulches plus mulch-free treatment) was performed. Also, for fresh weight and shoot number for the three grass weeds a split-plot factorial approach (growing season x cover crop mulches plus mulch-free treatment x inter-row cultivation) was used. Plant or shoot number and fresh weight data of the grass weeds before the ANOVA were {surd}(x + 1)- and log(x + 1)-transformed, respectively, to reduce their heterogeneity, but means presented are back-transformed values. The TNCB, POCB, and CLY data were analyzed by using a split-split-plot factorial approach (growing season x cover crop mulches plus mulch-free treatment x inter-row cultivation x herbicide application). Because the ANOVA indicated significant herbicide treatment effect on CLY, these data were analyzed separately for herbicide-free and herbicide treatments to estimate different LSD values. Furthermore, the single degree of freedom contrasts comparing the main effects of the three crop species (barley, rye, and triticale) on the emergence and growth of grass weeds, as well as on TNCB, POCB, and CLY were also performed. Fisher's protected LSD procedures were used to detect and separate mean treatment differences at P = 0.05.


   RESULTS AND DISCUSSION
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS AND DISCUSSION
CONCLUSIONS
 REFERENCES
 
Weed Response
The ANOVA performed for the data of the three weeds indicated no significant effect in most cases for growing season and growing season x treatments interaction (Tables 1 and 2). So, the means presented are averaged across growing season (Tables 3, 4, and 5).


View this table:
[in this window]
[in a new window]
  		Table 1. Analysis of variance of cotton, barnyardgrass, bristly foxtail, and large crabgrass plant number (3 WAP) as affected by winter cereal mulches during the 2002 to 2003 and 2003 to 2004 growing seasons. Plant number data of grass weeds before the ANOVA were {surd}(x + 1)-transformed.

 

View this table:
[in this window]
[in a new window]
  		Table 2. Analysis of variance of barnyardgrass, bristly foxtail, and large crabgrass shoot number and fresh weight (13 WAP) as affected by winter cereal mulches and inter-row cultivation during the 2002 to 2003 and 2003 to 2004 growing seasons. Shoot number and fresh weight data of the grass weeds before the ANOVA were {surd}(x + 1)- and log(x + 1)-transformed, respectively.

 

View this table:
[in this window]
[in a new window]
  		Table 3. Effect of 11 winter cereal cover crop mulches on emergence of barnyardgrass, bristly foxtail, and large crabgrass 3 WAP. Means are averaged across the 2002 to 2003 and 2003 to 2004 growing seasons.

 

View this table:
[in this window]
[in a new window]
  		Table 4. Effect of 11 winter cereal cover crop mulches on shoot number and fresh weight (13 WAP) of barnyardgrass, bristly foxtail, and large crabgrass grown in inter-row mechanically cultivated cotton. Means are averaged across the 2003 and 2004 growing seasons.

 

View this table:
[in this window]
[in a new window]
  		Table 5. Effect of 11 winter cereal cover crop mulches on shoot number and fresh weight (13 WAP) of barnyardgrass, bristly foxtail, and large crabgrass grown in noncultivated cotton. Means are averaged across the 2003 and 2004 growing seasons.

 
Only 4 to 6% of the weed seeds planted emerged 3 WAP. This fact could be attributed to reduced ability of weed seeds to emerge from a soil depth greater than 2 cm in which a great percentage of weed seeds had been incorporated (Benvenuti et al., 2001). Field conditions that affect dormancy of weed seeds could additionally account for this low weed emergence (Foley, 2001). Barnyardgrass, bristly foxtail, and large crabgrass densities averaged 36, 21, and 23 plants m–2, respectively, in mulch-free treatments (Table 3). This grass weed density was slightly greater than the typically observed in Greek cotton field. Cereal mulches reduced emergence compared to mulch-free treatments. Barley mulches generally caused the greatest emergence reduction whereas rye mulches had the least effect on germination, based on single degree of freedom contrasts (data not shown). For large crabgrass, triticale caused similar emergence reduction with barley, while for bristly foxtail, triticale caused similar emergence reduction with rye. Of the specific cereals tested, mulches of Athinaida barley, as well as Catria and Thisvi triticale resulted in the lowest grass densities (Table 3). The grass weed emergence reduction found during this study agrees with the results reported by Dhima et al. (2006) who studied the effect of winter cereal mulches on grass weeds in corn.

At 13 WAP, cereal mulches, in most cases, reduced the shoot number or the fresh weight of barnyardgrass, bristly foxtail, and large crabgrass compared to mulch-free treatments (Tables 4 and 5). Also, cultivated treatments caused greater reduction of shoot number and fresh weight of the three grass weeds compared to uncultivated treatments, based on single degree of freedom contrasts (Fig. 2 ). Barley mulches generally caused the greater reduction of barnyardgrass, bristly foxtail, and large crabgrass shoot number and fresh weight (Fig. 2). Of the specific cereals tested, mulches of Athinaida barley caused the greater shoot number and fresh weight reduction of the three weeds (Tables 4 and 5). At 16 WAP, barnyardgrass, bristly foxtail, and large crabgrass shoot number or fresh weight reduction caused by the 11 winter cereals, combined or not with inter-row cultivation was in most cases similar to that recorded at 13 WAP (Vasilakoglou et al., data not shown).


Figure 2
View larger version (22K):
[in this window]
[in a new window]
  		Fig. 2. Effect of cover crop residue and tillage on shoot number and fresh weight of barnyardgrass, bristly foxtail or large crabgrass 13 WAP. Columns within each graph with different letter indicate significant difference at P < 0.05. B, barley; R, rye; T, triticale; C, mulch-free (control).

 
The significant inhibition of barnyardgrass, bristly foxtail, and large crabgrass growth by the winter cereal cover crop mulches is in agreement with the results reported by Dhima et al. (2006). For most of the winter cereals in each weed species, the division of fresh weight by shoot number indicated no significant differences in these ratios, which means that winter cereal mulches reduced mainly the weed germination and had no adverse effect on growth of the survived weeds. This inhibition could be attributed to the greater amounts of allelochemicals found in the environment immediately after incorporation of winter cereals, which suppressed weed germination (Khanh et al., 2005; Kobayashi et al., 2004; Moore et al., 1994). However, the lack of significant adverse effect on growth of the survived weeds could be attributed either to the reduced amounts of allelochemicals in the environment as a result of their decomposition or to the increased ability of the survived weeds to tolerate the allelochemicals. Kobayashi et al. (2004) reported that winter barley suppressed emergence of summer annual weeds in soybean. Also, Nagabhushana et al. (2001) reported that rye was the most weed-suppressing cover crop among several small grains, while Reddy (2001) found that rye, oat (Avena sativa L.), wheat (Triticum aestivum L.), and hairy vetch (Vicia villosa Roth.) cover crop residues suppressed browntop millet [Brachiaria ramosa (L.) Stapf.] in soybean. Barnes and Putnam (1983) and Weston (1990) found that cover crops such as rye, barley, and wheat reduced early season biomass of various weeds by 48 to 98%, compared to no-cover crop controls. In contrast, Reddy (2001) and Teasdale et al. (1991) reported that large crabgrass density was not affected by rye residue compared with no-cover crop. Differences in susceptibility to rye allelochemicals among large crabgrass biotypes tested during these experiments could account for the lack of inhibitory effects on weed density.

Cotton Response
Cotton emergence was not significantly affected by the presence of cover crop mulches (Table 1) agreeing with studies on rye and cotton emergence conducted by Nyakatawa and Reddy (2000) and Reddy et al. (2004). Also, the ANOVA for the other measured parameters of cotton indicated no significant effect for growing season x cover crop mulches and growing season x cover crop mulches x inter-row cultivation x herbicide application interactions (Table 6). So, the cover crop mulches x inter-row cultivation x herbicide application interaction means of cotton yield are presented (Table 7).


View this table:
[in this window]
[in a new window]
  		Table 6. Analysis of variance of TNCB, POCB, and CLY as affected by winter cereal mulches, inter-row cultivation, and herbicide application during the 2002 to 2003 and 2003 to 2004 growing seasons.

 

View this table:
[in this window]
[in a new window]
  		Table 7. Effect of 11 winter cereal cover crop mulches and inter-row cultivation on CLY in herbicide treated or untreated cotton. Means are averaged across the 2003 and 2004 growing seasons.

 
Cotton in inter-row cultivated treatments had greater TNCB than in the uncultivated treatments, based on single degree of freedom contrasts (Fig. 3 ). Also, TNCB in herbicide treatments was greater than that in the herbicide-free treatments. In barley mulched-cultivated-herbicide and barley mulched-uncultivated-herbicide treatments, TNCB was greater than that in the corresponding rye-mulched, triticale-mulched, or mulch-free treatments (Fig. 3). In addition, in uncultivated-herbicide-free treatments, TNCB or POCB was similar among the cereal mulched treatments, but greater than that in the corresponding mulch-free treatments. However, in cereal-mulched-cultivated-herbicide-free treatments, TNCB or POCB was not significantly greater than that in the mulch-free-cultivated-herbicide-free treatments (Fig. 3). This result is in agreement with that reported by Reddy et al. (2004) who found that cotton boll number was not affected by rye cover crop. On the contrary, Nyakatawa et al. (2000) reported that cotton plants in rye-mulched treatments, had four more bolls per plant than those grown under mulch-free treatments. In most cases, the cultivated-herbicide treatments had similar POCB compared with the uncultivated-herbicide treatments (Fig. 3). However, this was not the case in uncultivated-herbicide treatments where POCB was greater than in uncultivated herbicide-free treatments.


Figure 3
View larger version (22K):
[in this window]
[in a new window]
  		Fig. 3. Inhibitory effect of three cover crop species and three grass weeds (barnyardgrass, bristly foxtail, and large crabgrass) on total number of cotton bolls (TNCB), percentage of open cotton bolls (POCB), and cotton lint yield (CLY) in inter-row cultivated and no-cultivated plots. Columns within each graph with different letter indicate significant difference at P < 0.05. B, barley; R, rye; T, triticale; C, mulch-free (control).

 
Cotton in the inter-row cultivated treatments generally provided greater CLY than in the uncultivated treatments, based on single degree of freedom contrasts (Fig. 3). Furthermore, cotton produced up to 4.5 times more lint yield in herbicide treatments as compared to herbicide-free treatments. Also, in inter-row cultivated-herbicide- and uncultivated-herbicide-free treatments, barley mulches produced the greatest CLY. In particular, in barley mulched-cultivated-herbicide treatments or in barley-mulched-uncultivated-herbicide-free treatments, CLY was increased up to 17 or 138%, respectively, compared with that in corresponding cereal mulch-free treatments (Table 7). The cereal-mulched-cultivated-herbicide-free treatments increased CLY by 28 to 84% compared to mulch-free-cultivated-herbicide-free treatments, while the CLY produced in rye-mulched treatments was similar with that in barley-mulched treatments. In cereal mulched-uncultivated-herbicide treatments, CLY was increased up to 35% compared with that in the mulch-free-uncultivated-herbicide treatments (Table 7).

The better soil condition combined with the reduced weed density resulted from the inter-row cultivation could account for the greater CLY produced in inter-row cultivated treatments compared to that in the corresponding uncultivated treatments (Christidis and Harrison, 1955; Upchurch and Selman, 1968).

The slightly greater CLY in barley-mulched-herbicide treatments compared to that in rye-mulched-herbicide, triticale-mulched-herbicide, or mulch-free-herbicide treatments could be attributed to the reduced crop competition from the three grass weeds during the early growth stages. These results are in contrast with those reported by Reddy (2001) who found that cover crop residues did not significantly affect soybean yield in treatments where weeds had been controlled by postapplied herbicides. Dhima et al. (2006) also reported that corn silage yields in cereals mulched-herbicide treatments were similar to corn yields in mulch-free-herbicide treatments.

The CLY increase in cereal-mulched-herbicide-free treatments is in contrast with the results reported by Brown et al. (1985) and Keeling et al. (1989) who did not find significant increases in cotton yield after planting into rye or wheat cover crops. However, Shrestha et al. (2002) reported that soybean yield was increased by the presence of rye and corn used as cover crops. Also, Moore et al. (1994) reported that soybean yield of rye and triticale mulch treatments were 69 and 91% greater, respectively, than that obtained in the bare soil treatment. In addition, Swanton et al. (1999) found that corn yield was increased by a rye cover crop.

The different effect of barley on CLY, compared with that of the other winter cereals studied, could be attributed to their greater inhibition of weed emergence. Greater amounts and higher phytotoxicity of the allelochemicals produced by barley could account for these differences (Ben-Hammouda et al., 2001; Dhima et al., 2006; Liu and Lovett, 1993).

Although an economic analysis was not conducted, it is worth mentioning that the estimated cost of winter cereal mulching (seedbed preparation, planting, cereal seed for planting, fertilizer, and labor time) is approximately $240 ha–1. This cost corresponds to 0.116 Mg cotton lint ha–1 (estimated on cotton price including subsides) and is lower than the economic profit that resulted from the yield increase (0.39 Mg cotton lint ha–1) of cotton grown in barley-mulched-cultivated-herbicide-free treatments (compared to mulch-free-cultivated-herbicide-free treatments). However, although winter cereal cover crop mulches provide an additional environmental benefit related to their ability to reduce herbicide use, improved soil water retention and increase soil organic matter, the averaged 37% cotton yield reduction recorded in cultivated-herbicide-free treated cotton compared to best cultivated-herbicide treated indicates that the application of herbicide on cotton grown in cereal-mulched treatments is unavoidable for cotton producers to be satisfied.


   CONCLUSIONS
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS AND DISCUSSION
 CONCLUSIONS
REFERENCES
 
The results of this study show that some rye populations and barley or triticale cultivars have the ability to suppress germination of weed seeds introduced in a field (none of the plots had any native seedbank), but none of them have any effect on the initial growth of the survived annual grass weeds such as barnyardgrass, bristly foxtail, and large crabgrass. The cover crops weed suppressive ability combined with inter-row cultivation could increase cotton yield, but for the greatest cotton yield a postemergence herbicide application is needed. Despite the fact that the planting of winter cereals requires an additional cost, their use as cover crop mulches, particularly in fields infested by lower grass weed population than that studied, could result in reduced herbicide usage and consequently to heighten environmental benefits. However, for cotton producers, this weed control is not adequate and consequently a herbicide application is required.


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





This Article
Right arrow Abstract Freely available
Right arrow Figures Only
Right arrow Full Text (PDF)
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 Google Scholar
Google Scholar
Right arrow Articles by Vasilakoglou, I.
Right arrow Articles by Lithourgidis, A.
Right arrow Search for Related Content
PubMed
Right arrow Articles by Vasilakoglou, I.
Right arrow Articles by Lithourgidis, A.
Agricola
Right arrow Articles by Vasilakoglou, I.
Right arrow Articles by Lithourgidis, A.
Related Collections
Right arrow Tillage
Right arrow Weed Management
Right arrow Allelopathy
Right arrow Cover Crops
Right arrow Cotton

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