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The effect of seedbed design on sorghumproduction in an arid environment
Journal of Arid Environments(1995) 29:317-324
The effect of seedbed design on sorghum production in an arid environment
Timothy A. Wiggins Department of Agricuhural Mechanization, College of Agricuhure, Sultan Qaboos University, P.O. Box 34, Al-Khod 123, Muscat, Sultanate of Oman (Received 17July 1993, accepted 21 September 1993) This paper discusses the effects of three different seedbed designs (furrow, ridge, and flatbed) on the production of sorghum under the harsh arid environment of the Sultanate of Oman. The demand for forage crops has risen significantly during the past decade in the Sultanate coinciding with the dramatic increase in milk- and meat-producing animals. Techniques for tillage of the seedbed have also changed with the introduction of new types of agricultural machinery for production of forage crops. Research relative to tillage techniques for seedbed preparation for the production of forage crops is required to meet the rising demand. The results of this study indicate that sorghum samples planted and grown on the ridge yielded the highest results relative to all categories; number of leaves, number of tillers, root length, plant height, and fresh and dry weight. It produced significantly higher mean results in the categories of root length, plant height, and fresh and dry weight compared with both the flatbed and furrow tillage method. Sorghum samples from the flatbed treatment area significantly outperformed sorghum samples from the furrow treatment area relative to the mean number of plant tillers, and mean fresh weight and mean dry weight. Sorghum samples from the furrow treatment area had significantly more leaves than samples from the flatbed treatment area.
Keywords: seedbed design; tillage techniques; sorghum production; Oman
Introduction T h e m e t h o d s and objectives of tillage practices vary f r o m one row-crop to another and
from farm to farm all across the globe. But regardless of the situation, the primary objectives of preplant and planting tillage operations are to improve seedbed environment, and to provide a known pattern of favourable and unfavourable locations (Klepper et al., 1989). Effective tillage and planting systems create soil conditions favourable for water infiltration, seed germination, plant emergence, early growth, and root development (Benjamin et al., 1992). The fundamental effect of any tillage operation utilized in the preparation of the seedbed is to change the soil condition relative to changes in the soil, air and water distribution, resistance to the penetration of roots, and erosion and weed control characteristics. The overall success of the tillage operation depends on how the interactions between the above parameters are combined to achieve good crop growth and yield at an acceptable cost in terms of inputs and soil deterioration (Anazodo et al., 1991). 0140-1963/95/030317 + 08 $08'00/0
© 1995 Academic Press Limited
318
T.A. WIGGINS
Agricultural scientists are aware of the benefits of preplant tillage operations on the production of forage crops, but relative research has often yielded conflicting results. Ehlers (1980) concluded from experiments that tillage may change soil bulk density, shoot and root growth and the water uptake pattern of a crop. Studies by Jones et al. (1969), Wittmus & Yazar (1980), and Blevins (1983) reported that yield increases with conservation preplant tillage systems were due to increases in soil moisture in the soil profile. Kanwar (1989) reported, however, that tillage systems do not always significantly affect the soil-water tension in the surface layer (0 to 3 m) of the soil. Chaplin et al. (1986) found no significant effect of preplant-tillage systems (moidboard plow, chisel plow, ridge plant and no-till) in sandy soil on irrigated corn or soybean grain yields. Henry et al. (1976) found that conservation tillage practices resulted in lower yields on poorly drained soils and produced higher yields on well-drained soils. He concluded that the yield potential of different preplant tillage systems is site specific. The production outcome of a crop often depends more on the seedbed environment itself, as created by weather history, previous tillage, and planting and tillage equipment at seeding, than on the preplant tillage techniques. A harsh seedbed environment may kill the seedling or stress it severely enough to limit the plant's productive potential (Klepper et al., 1989), negating any benefit of the tillage system employed. Factors such as soil temperature, moisture, compaction, concentrations of chemicals and aeration can independently or interactively cause harsh seedbeds and result in poor plant stands (Klepper et al., 1989). Plant stress, whether caused by poor seed quality or imposed by the seedbed, delays emergence, slows the rate of emergence and decreases the final stand counts (Klepper et al., 1989). Pidgeon (1982) concluded that plants require a continuous pore system, adequate for drainage and root development, and that soil should have a structure that does not collapse from implement weight or from natural processes (Benjamin et al., 1992). Seedbed design and the method of planting may have more of an effect on the seedbed environment than any of the preplant tillage systems employed. On the Arabian continent, the demand for forage crops for consumption by livestock has increased significantly in the past 20 years, due to a dramatic population increase and the resultant increase in the number of milk- and meat-producing animals (Alyaeesh et al., 1988). A gradual change has also occurred in the thinking and the farming methods of the Arabian farmer moving from traditional, low productivity farming to a modern, highpotential productivity farming subjected to technological limitations (Younis, 1986). This has resulted in the need for research relative to the application of effective tillage and seedbed preparation techniques for forage crop production in an arid environment. In 1986, the Sultan Qaboos University was established with a mandate to conduct agricultural research relative to the specific needs and resources encountered in the harsh arid-environment of the Sultanate. The climate in the Sultanate of Oman is characterized by extremely high growing season temperatures, high humidity, high solar irradiance, and high salinity. The most important limiting factor for crop production is the availability of water for agricultural use. The demand for water continues to escalate, not only for increased agricultural production, but for domestic use by the growing population. Because of this, the water-table is declining at an alarming rate. The result has been salt water intrusion into the existing ground-water supply along the coastal area. When water is limited, optimum crop production requires a soil condition that allows crop roots to use available water (Benjamin et al., 1992). Efficient utilization of this important and limited resource requires research on forage crops which have a high wateruse efficiency and can adapt to the harsh environment of Oman and its neighbors (Alyaeesh et al., 1988). Most of the animal feed containing protein-rich ingredients are imported at high cost by the government and supplied to farmers at subsidized rates. Alfalfa and Rhodes grass are the primary crops grown for forage production in the Sultanate, with sorghum, Sudan grass and maize filling in the gaps to a lesser degree. Research is needed to identify alternative forage grasses which will boost the rate of forage production to meet the rising
SEEDBED DESIGN
319
demand and to reduce the import of expensive feed material. Sorghum appears to be a responsive alternative to be grown under arid conditions for the production of forage material (Foale & Myers, 1980, 1981; Jones 1987). In response to research needs relative to the production of forage material for livestock consumption, this study was undertaken to compare the effects of three different seedbed designs (ridge, furrow and flatbed) on the production of sorghum under arid conditions in the Sultanate of Oman.
Materials and m e t h o d s The experiment spanned two successive growing seasons (1991-92) on the Sultan Qaboos University research farm in Muscat, Sultanate of Oman. A disk-harrow was utilized to prepare the soil for seedbed construction. Seedbeds were then prepared utilizing three different construction techniques (furrow, ridge, and flatbed designs). The height of the ridges and depth of the furrows was approximately 15 cm. Adjacent research plots were selected which contain the sandy-loam type soil representative of the farming region. Sorghum was planted at identical rates in the furrow row in one plot, on the ridge row in the second, and on the flatbed row in the third. All plots received identical treatment of nutrients, water (sprinkler irrigation), and insecticides. Further tillage was not employed after the initial seedbed preparation to preserve the tillage design. Weeding was accomplished by hand for the same reason. Ten random samples were taken from each treatment area at the end of the growth period for a total of 20 samples per area, or 60 samples total. The results of the tillage process as indicated by the seedbed conditions were assessed by comparisons of plant fresh weight (Bhatt & Evans, 1977), plant dry weight (Lowe & Ries, 1972), leaf area (Lowe & Ries, 1972), plant height, number of tillers, and number of leaves. Analysis of Variance and the Newman-Keuls Multiple Comparisons test were utilized for statistical analysis.
Results and d i s c u s s i o n
Analysis of the data revealed a significant difference between the three seedbed design groups when comparing the number of leaves produced (Table 1). A significant difference was indicated between the plants in the furrow and ridge groups compared with those in the flatbed area group (Fig. i). Those plants from the flatbed area had significantly fewer leaves than those from the furrow and ridge treatment areas. No significant difference was indicated between the furrow and ridge treatments relative to the number of leaves produced. The mean number of tillers per plant for the samples taken from the three treatment areas are indicated in Table 2. A significant difference was found between the plants in the flatbed and ridge treatment groups and those in the furrow treatment (Fig. 2). While no
Table I. Number of leaves comparison
Flat Furrow Ridge
Mean number of leaves
Standard deviation
5"3 6"8 7"3
1"218 * 1"281 "1'455
* Indicatesa significantdifferenceat 0"05. F = 12"40;p<0"001;df.= 59.
T. A. WIGGINS
320 0-00
3.00
6"00
Flat
+
Furrow
i
Ridge
i
9"00
12"00
i
Figure 1. N u m b e r of leaves distribution ( + indicates the mean).
T a b l e 2.
Number of tiUerscomparison
Flat Furrow Ridge
Mean n u m b e r oftiUers
Standard deviation
4"3 1'9 4"6
* 1"302 1"410 * 1"729
• Indicatesa significantdifferenceat 0"05. F = 19"69;p<0"001;df. = 59.
0"00
2"00
Flat
4"00
+
6"00
I
Furrow Ridge
Figure 2. N u m b e r of tillers distribution ( + indicates the mean).
T a b l e 3.
Flat Furrow Ridge
Length of root comparison Mean length (cm)
Standard deviation
22"75 22" 76 29"20
1"674 2" 174 *4"450
Indicatesa significantdifferenceat 0"05. F = 30"40;p<0"001;df. = 59.
8"00
SEEDBED 15.0(}
21"00
321
DESIGN 27"00
33"00
39"00
Flat
Furrow Ridge
+
Figure 3. Length (cm) of root distribution (+ indicates the mean).
significant difference was indicated between the mean number of tillers on the plants from the flatbed and ridge areas (4"3 and 4"6 tillers respectively), the plants from the furrow area had significantly fewer tillers (1"9 tillers) compared with the other two treatments. Sorghum planted and grown on the flatbed and ridge seedbed design areas produced significantly more tillers than sorghum planted and grown in the furrow seedbed design area. Data relative to mean root length for each of the three treatment methods are shown in Table 3. No significant difference was found between the flatbed and furrow plant samples (Fig. 3). A significant difference in root length was indicated, however, between the samples from the ridge treatment group and those from the other two treatments. The roots of the sorghum plants planted and grown on the ridge were significantly longer than those of the flatbed and furrow treatments. Results of the data indicate that the roots of the
Table 4. Height comparison Mean height (cm) Flat
Furrow Ridge
Standard deviation
86'45
8"818
83"05 105"15
17"411 *9"021
* Indicates a significant difference at 0"05. F = 1 8 " 3 8 ; p < 0 " 0 0 1 ; d f . = 59.
55
72
~9
Flat
Furrow
106
i
+
I
+
t
Ridge
Figure 4. Height (cm) distribution (+ indicates the mean).
123
T. A. WIGGINS
322
Table 5. Fresh weight comparison
Flat Furrow Ridge
Mean fresh weight (grams)
Standard deviation
133"230 52' 487 203-589
~24-696 ~ 17"247 ~78"031
Indicates a significant difference at 0"05. F = 4 9 ' 0 3 ; p < 0 " 0 0 1 ; d f . = 59.
20
104
188
272
356
Flat Furrow
I
Ridge
Figure 5. Fresh weight (g) distribution (+ indicates the mean).
sorghum samples from the ridge treatment area had a mean growth in excess of 25% longer than those in the flatbed and furrow areas. Results of the data for mean plant height for each of the three treatment methods are indicated in Table 4. A significant difference was found between sorghum samples planted and grown on the ridge with those from the furrow and flatbed treatments (Fig. 4). Sorghum planted and grown on the ridge grew significantly taller than that on the flatbed or furrow. There was no significant difference in plant height between the sorghum samples grown on the flatbed and furrow areas. A factor which may have contributed to the increased leaves, tillers, root length and height of the plants grown on the ridge compared with the other two methods is the physical composition of the soil. There is generally between 30 to 40 cm of top soil present on the plots from which most stones have been removed. Although no plough-pan was present, the layer below contained stones which may have been of a sufficient quantity to have hampered root development and/or penetration. As the sorghum planted on the ridge had a greater depth of soil in which to develop before reaching the rock-laden stratum, it may have been a contributing factor to its overall superior development. A significant difference was found between all groups when comparing the mean fresh weight for the plant samples from the three treatment areas (Table 5). As illustrated in Fig. 5, sorghum planted and grown on the ridge produced the significantly highest mean fresh weight, followed second by sorghum in the flatbed treatment, with the furrow treatment indicating the lowest fresh weight of the three. The results indicate that the sorghum samples from the ridge treatment had over twice the mean fresh weight than the samples from the flatbed treatment area, and almost four times that of the sorghum samples from the furrow treatment area. The results of the data for comparison of the three treatment groups relative to mean dry weight paralleled that of the fresh weight comparison. A significant difference was again indicated between all three groups (Table 6). As illustrated in Fig. 6, the mean dry weight
SEEDBED
DESIGN
323
Table 6. Dry weight comparison Mean dry weight (grams)
Standai:d deviation
47'748 16' 016 82 "468
+'763 +5-027 +29"249
Flat Furrow Ridge
Indicates a significant difference at 0"05. F = 7 0 " 4 3 ; p < 0 ' 0 0 1 ; d f . = 59.
38
Flat
71
104
137
{N
Furrow
Ridge
Figure 6. Dry weight (g) distribution (+ indicates the mean).
of sorghum samples from the ridge treatment area was significantly higher, followed second by that in the flatbed treatment area, with the furrow treatment indicating the lowest mean dry weight of the three.
Summary The objective of this study was to compare the effects of three seedbed tillage designs on the production of sorghum under arid conditions. Results of the analysis indicate that sorghum samples planted and grown on the ridge yielded higher mean results relative to all categories. It produced significantly higher results in the mean categories of root length, plant height, and fresh and dry weight compared with both the furrow and flatbed tillage methods. The sorghum samples from the ridge treatment also produced significantly more leaves than samples from the flatbed treatment, and significantly more tillers than samples from the furrow treatment. Sorghum samples from the furrow treatment outperformed those in the flatbed treatment relative to the number of leaves. However, sorghum samples from the flatbed treatment significantly outperformed samples from the furrow treatment relative to the number of plant tillers, and fresh and dry weight. In summary, of the three seedbed tillage designs for sorghum production in a harsh arid environment, results indicate that the ridge method is significantly more productive than the flatbed or furrow techniques. With all other factors being equal (water, sunlight, nutrients, insecticide, etc.), the ridge design produced significantly more sorghum forage material than the other two techniques.
324
T. A. WIGGINS
References Alyaeesh, F., Bokhari, U. G. & AI-Noori, M. (1988). Potentials of forage crops in Saudi Arabia. Arab GulfJournal of Scientific Research. Agricultural: Biological. Science, B6: 359-367. Anazodo, U. G. N., Onwualu, A. P. & Watts, K. C. (1991). Evaluation of alternative tillage systems in the absence of herbicides for maize production in a Savannah loamy sand. Journal of Agricultural Engineering Research, 49: 259-272. Baruchin, A., Dinar, A. & Yaron, D. (1992). Alternative cropping systems and intensive irrigation under arid zone conditions. AgriculturalSystems, 38: 301-318. Benjamin, J. G., Choi, C. H., Cruse, R. M., Elamin, M. A., Erbach, D. C. & Mukhtar, S. (1992). Soil and corn response to tillage with paraplow. Transactionsof the A.S.A.E., 35: 1347-1354. Bhatt, G. M. & Evans, L. E. (1977). A nondestructive technique for measuring seedling vigor in wheat. CanadianJournal of Plant Science, 57: 983-985. Blevins, R. L. (1983). Changes in soil properties after 10 years continuous non-tilled and conventionally tilled corn. Soil Tillage Research, 3:135-146. Chaplin, J., Lueders, M. & Rugg, D. (1986). A study of compaction and crop yields on loamy sand soil after seven years of reduced tillage. Transactionsof the A.S.A.E., 29: 389-392. Ehlers, W. (1980). Tillage effects on root development, water uptake and growth of oats. Soil Tillage Research, 1: 19-34. Foale, M. A. & Myers, R. J. K. (1980). Row spacing and population density in Austrahan grain sorghum production. Journal of Australian Agricultural Science, 46:214--220. Foale, M. A. & Myers, R. J. K. (1981). Row spacing and population density in grain sorghum a simple analysis. Field Crops Research, 4: 147-154. Henry, J. E., Triplett, G. B., Jr. & Van Doren, D. M. (1976). Influence on long-term tillage, crop rotation, and soil type combinations on corn yield. Soil Science Society of America Journal, 40: 100-105. Jones, J. N., Jr., Moody, J. E. & Lillard, J. H. (1969). Effects of tillage, no-tillage and mulch on soil water and plant growth. AgronomyJournal, 61:719-721. Jones, M. J. (1987). Plant population, rainfall and sorghum production in Botswana. 1. Results of experiment station trials. Experimental Agriculture, 23: 335-347. Kanwar, R. S. (1989). Effect of tillage system on the variability of soil-water tensions and soil-water content. Transectionsof the A.S.A.E., 32: 605-610. Klepper, B., Rickman, R. W. & Wilkins, D. E. (1989). Measuring wheat seedhng response to tillage and seeding systems. Transactionsof the A.S.A.E., 32: 795-800. Lowe, L. B. & Ries, S. K. (1972). Effects of environment on the relation between seed protein and seedling vigor in wheat. CanadianJournal of Plant Science, 52: 157-164. Pidgeon, J. D. (1982). Paraplow - - A rational approach to soil management. Proceedings of the 9th Conferenceof the InternationaISoil TillageResearch Organization,pp. 633-638. ISTRO, Osijek, Yugoslavia. Wittmus, H. & Yazar, A. (1980). Moisture storage, water use and corn yield for seven tillage systems under water stress. Proceedings of Crop Production with Convention in the 80's. pp. 66-75. St. Joseph, MI: A.S.A.E. Younis, S. N. A. (1986). System approach to machinery selection (Saudi agriculture case). Arabian GulfJournal of Scientific Research, 4: 679-691.
The effect of seedbed design on sorghum production in an arid environment
Timothy A. Wiggins Department of Agricuhural Mechanization, College of Agricuhure, Sultan Qaboos University, P.O. Box 34, Al-Khod 123, Muscat, Sultanate of Oman (Received 17July 1993, accepted 21 September 1993) This paper discusses the effects of three different seedbed designs (furrow, ridge, and flatbed) on the production of sorghum under the harsh arid environment of the Sultanate of Oman. The demand for forage crops has risen significantly during the past decade in the Sultanate coinciding with the dramatic increase in milk- and meat-producing animals. Techniques for tillage of the seedbed have also changed with the introduction of new types of agricultural machinery for production of forage crops. Research relative to tillage techniques for seedbed preparation for the production of forage crops is required to meet the rising demand. The results of this study indicate that sorghum samples planted and grown on the ridge yielded the highest results relative to all categories; number of leaves, number of tillers, root length, plant height, and fresh and dry weight. It produced significantly higher mean results in the categories of root length, plant height, and fresh and dry weight compared with both the flatbed and furrow tillage method. Sorghum samples from the flatbed treatment area significantly outperformed sorghum samples from the furrow treatment area relative to the mean number of plant tillers, and mean fresh weight and mean dry weight. Sorghum samples from the furrow treatment area had significantly more leaves than samples from the flatbed treatment area.
Keywords: seedbed design; tillage techniques; sorghum production; Oman
Introduction T h e m e t h o d s and objectives of tillage practices vary f r o m one row-crop to another and
from farm to farm all across the globe. But regardless of the situation, the primary objectives of preplant and planting tillage operations are to improve seedbed environment, and to provide a known pattern of favourable and unfavourable locations (Klepper et al., 1989). Effective tillage and planting systems create soil conditions favourable for water infiltration, seed germination, plant emergence, early growth, and root development (Benjamin et al., 1992). The fundamental effect of any tillage operation utilized in the preparation of the seedbed is to change the soil condition relative to changes in the soil, air and water distribution, resistance to the penetration of roots, and erosion and weed control characteristics. The overall success of the tillage operation depends on how the interactions between the above parameters are combined to achieve good crop growth and yield at an acceptable cost in terms of inputs and soil deterioration (Anazodo et al., 1991). 0140-1963/95/030317 + 08 $08'00/0
© 1995 Academic Press Limited
318
T.A. WIGGINS
Agricultural scientists are aware of the benefits of preplant tillage operations on the production of forage crops, but relative research has often yielded conflicting results. Ehlers (1980) concluded from experiments that tillage may change soil bulk density, shoot and root growth and the water uptake pattern of a crop. Studies by Jones et al. (1969), Wittmus & Yazar (1980), and Blevins (1983) reported that yield increases with conservation preplant tillage systems were due to increases in soil moisture in the soil profile. Kanwar (1989) reported, however, that tillage systems do not always significantly affect the soil-water tension in the surface layer (0 to 3 m) of the soil. Chaplin et al. (1986) found no significant effect of preplant-tillage systems (moidboard plow, chisel plow, ridge plant and no-till) in sandy soil on irrigated corn or soybean grain yields. Henry et al. (1976) found that conservation tillage practices resulted in lower yields on poorly drained soils and produced higher yields on well-drained soils. He concluded that the yield potential of different preplant tillage systems is site specific. The production outcome of a crop often depends more on the seedbed environment itself, as created by weather history, previous tillage, and planting and tillage equipment at seeding, than on the preplant tillage techniques. A harsh seedbed environment may kill the seedling or stress it severely enough to limit the plant's productive potential (Klepper et al., 1989), negating any benefit of the tillage system employed. Factors such as soil temperature, moisture, compaction, concentrations of chemicals and aeration can independently or interactively cause harsh seedbeds and result in poor plant stands (Klepper et al., 1989). Plant stress, whether caused by poor seed quality or imposed by the seedbed, delays emergence, slows the rate of emergence and decreases the final stand counts (Klepper et al., 1989). Pidgeon (1982) concluded that plants require a continuous pore system, adequate for drainage and root development, and that soil should have a structure that does not collapse from implement weight or from natural processes (Benjamin et al., 1992). Seedbed design and the method of planting may have more of an effect on the seedbed environment than any of the preplant tillage systems employed. On the Arabian continent, the demand for forage crops for consumption by livestock has increased significantly in the past 20 years, due to a dramatic population increase and the resultant increase in the number of milk- and meat-producing animals (Alyaeesh et al., 1988). A gradual change has also occurred in the thinking and the farming methods of the Arabian farmer moving from traditional, low productivity farming to a modern, highpotential productivity farming subjected to technological limitations (Younis, 1986). This has resulted in the need for research relative to the application of effective tillage and seedbed preparation techniques for forage crop production in an arid environment. In 1986, the Sultan Qaboos University was established with a mandate to conduct agricultural research relative to the specific needs and resources encountered in the harsh arid-environment of the Sultanate. The climate in the Sultanate of Oman is characterized by extremely high growing season temperatures, high humidity, high solar irradiance, and high salinity. The most important limiting factor for crop production is the availability of water for agricultural use. The demand for water continues to escalate, not only for increased agricultural production, but for domestic use by the growing population. Because of this, the water-table is declining at an alarming rate. The result has been salt water intrusion into the existing ground-water supply along the coastal area. When water is limited, optimum crop production requires a soil condition that allows crop roots to use available water (Benjamin et al., 1992). Efficient utilization of this important and limited resource requires research on forage crops which have a high wateruse efficiency and can adapt to the harsh environment of Oman and its neighbors (Alyaeesh et al., 1988). Most of the animal feed containing protein-rich ingredients are imported at high cost by the government and supplied to farmers at subsidized rates. Alfalfa and Rhodes grass are the primary crops grown for forage production in the Sultanate, with sorghum, Sudan grass and maize filling in the gaps to a lesser degree. Research is needed to identify alternative forage grasses which will boost the rate of forage production to meet the rising
SEEDBED DESIGN
319
demand and to reduce the import of expensive feed material. Sorghum appears to be a responsive alternative to be grown under arid conditions for the production of forage material (Foale & Myers, 1980, 1981; Jones 1987). In response to research needs relative to the production of forage material for livestock consumption, this study was undertaken to compare the effects of three different seedbed designs (ridge, furrow and flatbed) on the production of sorghum under arid conditions in the Sultanate of Oman.
Materials and m e t h o d s The experiment spanned two successive growing seasons (1991-92) on the Sultan Qaboos University research farm in Muscat, Sultanate of Oman. A disk-harrow was utilized to prepare the soil for seedbed construction. Seedbeds were then prepared utilizing three different construction techniques (furrow, ridge, and flatbed designs). The height of the ridges and depth of the furrows was approximately 15 cm. Adjacent research plots were selected which contain the sandy-loam type soil representative of the farming region. Sorghum was planted at identical rates in the furrow row in one plot, on the ridge row in the second, and on the flatbed row in the third. All plots received identical treatment of nutrients, water (sprinkler irrigation), and insecticides. Further tillage was not employed after the initial seedbed preparation to preserve the tillage design. Weeding was accomplished by hand for the same reason. Ten random samples were taken from each treatment area at the end of the growth period for a total of 20 samples per area, or 60 samples total. The results of the tillage process as indicated by the seedbed conditions were assessed by comparisons of plant fresh weight (Bhatt & Evans, 1977), plant dry weight (Lowe & Ries, 1972), leaf area (Lowe & Ries, 1972), plant height, number of tillers, and number of leaves. Analysis of Variance and the Newman-Keuls Multiple Comparisons test were utilized for statistical analysis.
Results and d i s c u s s i o n
Analysis of the data revealed a significant difference between the three seedbed design groups when comparing the number of leaves produced (Table 1). A significant difference was indicated between the plants in the furrow and ridge groups compared with those in the flatbed area group (Fig. i). Those plants from the flatbed area had significantly fewer leaves than those from the furrow and ridge treatment areas. No significant difference was indicated between the furrow and ridge treatments relative to the number of leaves produced. The mean number of tillers per plant for the samples taken from the three treatment areas are indicated in Table 2. A significant difference was found between the plants in the flatbed and ridge treatment groups and those in the furrow treatment (Fig. 2). While no
Table I. Number of leaves comparison
Flat Furrow Ridge
Mean number of leaves
Standard deviation
5"3 6"8 7"3
1"218 * 1"281 "1'455
* Indicatesa significantdifferenceat 0"05. F = 12"40;p<0"001;df.= 59.
T. A. WIGGINS
320 0-00
3.00
6"00
Flat
+
Furrow
i
Ridge
i
9"00
12"00
i
Figure 1. N u m b e r of leaves distribution ( + indicates the mean).
T a b l e 2.
Number of tiUerscomparison
Flat Furrow Ridge
Mean n u m b e r oftiUers
Standard deviation
4"3 1'9 4"6
* 1"302 1"410 * 1"729
• Indicatesa significantdifferenceat 0"05. F = 19"69;p<0"001;df. = 59.
0"00
2"00
Flat
4"00
+
6"00
I
Furrow Ridge
Figure 2. N u m b e r of tillers distribution ( + indicates the mean).
T a b l e 3.
Flat Furrow Ridge
Length of root comparison Mean length (cm)
Standard deviation
22"75 22" 76 29"20
1"674 2" 174 *4"450
Indicatesa significantdifferenceat 0"05. F = 30"40;p<0"001;df. = 59.
8"00
SEEDBED 15.0(}
21"00
321
DESIGN 27"00
33"00
39"00
Flat
Furrow Ridge
+
Figure 3. Length (cm) of root distribution (+ indicates the mean).
significant difference was indicated between the mean number of tillers on the plants from the flatbed and ridge areas (4"3 and 4"6 tillers respectively), the plants from the furrow area had significantly fewer tillers (1"9 tillers) compared with the other two treatments. Sorghum planted and grown on the flatbed and ridge seedbed design areas produced significantly more tillers than sorghum planted and grown in the furrow seedbed design area. Data relative to mean root length for each of the three treatment methods are shown in Table 3. No significant difference was found between the flatbed and furrow plant samples (Fig. 3). A significant difference in root length was indicated, however, between the samples from the ridge treatment group and those from the other two treatments. The roots of the sorghum plants planted and grown on the ridge were significantly longer than those of the flatbed and furrow treatments. Results of the data indicate that the roots of the
Table 4. Height comparison Mean height (cm) Flat
Furrow Ridge
Standard deviation
86'45
8"818
83"05 105"15
17"411 *9"021
* Indicates a significant difference at 0"05. F = 1 8 " 3 8 ; p < 0 " 0 0 1 ; d f . = 59.
55
72
~9
Flat
Furrow
106
i
+
I
+
t
Ridge
Figure 4. Height (cm) distribution (+ indicates the mean).
123
T. A. WIGGINS
322
Table 5. Fresh weight comparison
Flat Furrow Ridge
Mean fresh weight (grams)
Standard deviation
133"230 52' 487 203-589
~24-696 ~ 17"247 ~78"031
Indicates a significant difference at 0"05. F = 4 9 ' 0 3 ; p < 0 " 0 0 1 ; d f . = 59.
20
104
188
272
356
Flat Furrow
I
Ridge
Figure 5. Fresh weight (g) distribution (+ indicates the mean).
sorghum samples from the ridge treatment area had a mean growth in excess of 25% longer than those in the flatbed and furrow areas. Results of the data for mean plant height for each of the three treatment methods are indicated in Table 4. A significant difference was found between sorghum samples planted and grown on the ridge with those from the furrow and flatbed treatments (Fig. 4). Sorghum planted and grown on the ridge grew significantly taller than that on the flatbed or furrow. There was no significant difference in plant height between the sorghum samples grown on the flatbed and furrow areas. A factor which may have contributed to the increased leaves, tillers, root length and height of the plants grown on the ridge compared with the other two methods is the physical composition of the soil. There is generally between 30 to 40 cm of top soil present on the plots from which most stones have been removed. Although no plough-pan was present, the layer below contained stones which may have been of a sufficient quantity to have hampered root development and/or penetration. As the sorghum planted on the ridge had a greater depth of soil in which to develop before reaching the rock-laden stratum, it may have been a contributing factor to its overall superior development. A significant difference was found between all groups when comparing the mean fresh weight for the plant samples from the three treatment areas (Table 5). As illustrated in Fig. 5, sorghum planted and grown on the ridge produced the significantly highest mean fresh weight, followed second by sorghum in the flatbed treatment, with the furrow treatment indicating the lowest fresh weight of the three. The results indicate that the sorghum samples from the ridge treatment had over twice the mean fresh weight than the samples from the flatbed treatment area, and almost four times that of the sorghum samples from the furrow treatment area. The results of the data for comparison of the three treatment groups relative to mean dry weight paralleled that of the fresh weight comparison. A significant difference was again indicated between all three groups (Table 6). As illustrated in Fig. 6, the mean dry weight
SEEDBED
DESIGN
323
Table 6. Dry weight comparison Mean dry weight (grams)
Standai:d deviation
47'748 16' 016 82 "468
+'763 +5-027 +29"249
Flat Furrow Ridge
Indicates a significant difference at 0"05. F = 7 0 " 4 3 ; p < 0 ' 0 0 1 ; d f . = 59.
38
Flat
71
104
137
{N
Furrow
Ridge
Figure 6. Dry weight (g) distribution (+ indicates the mean).
of sorghum samples from the ridge treatment area was significantly higher, followed second by that in the flatbed treatment area, with the furrow treatment indicating the lowest mean dry weight of the three.
Summary The objective of this study was to compare the effects of three seedbed tillage designs on the production of sorghum under arid conditions. Results of the analysis indicate that sorghum samples planted and grown on the ridge yielded higher mean results relative to all categories. It produced significantly higher results in the mean categories of root length, plant height, and fresh and dry weight compared with both the furrow and flatbed tillage methods. The sorghum samples from the ridge treatment also produced significantly more leaves than samples from the flatbed treatment, and significantly more tillers than samples from the furrow treatment. Sorghum samples from the furrow treatment outperformed those in the flatbed treatment relative to the number of leaves. However, sorghum samples from the flatbed treatment significantly outperformed samples from the furrow treatment relative to the number of plant tillers, and fresh and dry weight. In summary, of the three seedbed tillage designs for sorghum production in a harsh arid environment, results indicate that the ridge method is significantly more productive than the flatbed or furrow techniques. With all other factors being equal (water, sunlight, nutrients, insecticide, etc.), the ridge design produced significantly more sorghum forage material than the other two techniques.
324
T. A. WIGGINS
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