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Row spacing, water use, and yield of wheat (Triticum aestivum), barley (Hordeum vulgare) and faba bean (Vicia faba)

Samuel Kleemann and Gurjeet Gill

School of Agriculture, Food and Wine, The University of Adelaide, Roseworthy Campus, SA 5371.
www.adelaide.edu.au
Email samuel.kleemann@adelaide.edu.au

Abstract

A field experiment was undertaken in 2006 at Roseworthy, South Australia, to evaluate water use, growth and yield of wheat (cv. Pugsley), barley (cv. Sloop SA) and faba bean (cv. Fiesta) grown on conventional (18 cm) and wide-row spacings (36 and 54 cm). There were clear differences between crop species in their response to the different row spacings. The penalty in grain yield in cereals in 36 cm rows was only 2% for barley and 5% for wheat. However, this increased sharply to >20% when row spacing increased to 54 cm. In contrast the grain yield of faba bean increased significantly (P<0.05) at 36 (24%) and 54 cm (20%) relative to the 18 cm row spacing which yielded 0.79 t/ha. The yield increase in faba bean in wider rows was associated with greater number of pods per plant. Water use by wheat and barley over the growing season was unaffected by the row spacing. In contrast, faba beans grown in wider rows used 10-15 mm less water during the early vegetative phase than the crop grown at 18 cm row spacing. Faba bean grown in wide rows appeared to defer some of the water use into its reproductive phase. This change in water use pattern may have contributed to increased pod density and grain yields observed for these treatments in faba bean. These results provide some confidence that wide row cropping could be used for the management of difficult to control weeds with inter-row herbicide application without compromising crop yield and profitability.

Key Words

Wide-row cropping

Introduction

In recent years, farming practices in the southern Australian wheatbelt have undergone significant changes associated with the introduction of conservation tillage, stubble retention and precision guidance systems and the reduction in livestock numbers. In order to handle increasing stubble loads at sowing, some growers have cultivated crops on wider row spacings (>180 mm). Adoption of wide-row cropping has also been encouraged by reports of yield increases in pulse crops, such as lupin and chickpea (Felton et al.1996, French and Harries 2006), and the potential to control herbicide resistant weeds by inter-row spraying (Hashem et al. 2005). Furthermore stubble retention has been shown to significantly reduce soil moisture evaporation (Unger et al. 1991), and may contribute to improved water-use efficiency of crops grown on wide rows.

Research by Blackwell et al. (2006) reported that wheat performed better in wider rows on shallow soils in the northern wheat-belt of Western Australia because of deferred use of soil water between rows until later in grain filling, which resulted in less stress to the crop and greater grain fill. Similarly, French and Harries (2006) concluded that increased lupin yields in wide rows also resulted from deferred use of soil water until grain filling. However, reports of increased grain yield with wide rows is often in contradiction to much of the earlier research on crop row spacing in Australia (Burch 1986, Belford and Riethmuller 1992), which often reported higher crop yields with narrower spacings (<180 mm).

Since the adoption of stubble retention and wide row farming practices, there has been limited research investigating the performance of different crop species at wider rows. Here we report on a field experiment undertaken in South Australia in 2006, evaluating the effect of row spacing on water use and yield of wheat, barley and faba bean.

Methods

A field experiment was established in 2006 at Roseworthy (3432’S, 13841’E), South Australia, to evaluate water use, growth and yield of wheat (cv. Pugsley), barley (cv. SA Sloop) and faba bean (cv. Fiesta) grown on conventional (18 cm) and wide-row spacings (36 and 54 cm). The growing season rainfall (April-October) in 2006 was 180 mm, well below the long-term average of 330 mm. The experiment was planted on the 24th of May, with wheat, barley and faba bean sown at 90, 70 and 150 kg/ha into a standing stubble (4.0 t/ha) using a knife-point drill, in a randomised complete block with four replicates. Weeds were controlled with applications of residual and grass selective herbicides. Soil moisture was measured at monthly intervals by taking TDR readings from the soil surface (0-15 cm) and by neutron moisture probe (NMP) taking measurements to a depth of 130 cm in 1.5 m access tubes in the centre of each plot. Grain yield was determined using a small plot harvester.

Results

There were differences between crop species in their yield response to the different row spacing treatments (Figure 1). The penalty in grain yield in cereals in 36 cm rows was only 2% for barley and 5% for wheat. However, this yield penalty increased to >20% when row spacing increased to 54 cm. In contrast, the grain yield of faba bean increased significantly (P<0.05) at 36 (24%) and 54 cm (20%) relative to the 18 cm row spacing which yielded 0.79 t/ha.

Figure 1. Yield response of Pugsley wheat (™), Sloop SA barley (˜) and Fiesta faba bean (q) grown on 18, 36 and 54 cm row spacings at Roseworthy in 2006. Values in brackets are relative grain yield (%) compared to 18 cm spacing.

Extractable water through the soil to 130 cm depth showed small differences due to row spacing in May but larger ones due to crop type in October (Figure 2). Water use by wheat and barley over the growing season was unaffected by row spacing, however, both were more effective than faba bean at extracting soil water. In contrast to the cereals, faba bean used 50 mm less, which was related to its inability to extract water below 85 cm depth and its failure to dry soil below 20% volumetric water content. This additional soil water could be of benefit to the following wheat crop in dry seasons if it could be stored in the profile until the next growing season.

Figure 2. Change in volumetric soil water with depth from May (solid line) to October (dashed line) for Pugsley wheat (a), Sloop SA barley (b) and Fiesta faba bean (c) at three different row spacings (r, 18 cm; , 36 cm; , 54 cm) at Roseworthy in 2006.

Figure 3. Change in total soil water for Fiesta faba bean at three different row spacings (r, 18 cm; , 36 cm; , 54 cm) during the 2006 growing season. Arrow indicates start of flowering.

In contrast to wheat and barley, faba bean grown in wider rows used 10-15 mm less water between the rows during the early vegetative phase than the crop grown at 18 cm row spacing (Figure 3), deferring some of the water use until its reproductive phase. This change in water use pattern may have contributed to the increased pod density and subsequent grain yield responses observed for these treatments in faba bean (Figure 4.). French and Harries (2006) concluded that lupin in wide rows similarly deferred use of soil water between rows until later in grain filling and were therefore less stressed, and filled more grain.

Figure 4. Effect of row spacing on pod density (pods/m2) of Fiesta faba bean at Roseworthy in 2006.

Conclusion

In 2006, a dry season, the yield penalty with growing cereals on wide rows appears to be small, in contrast to faba bean which showed an increase in yield relative to the conventional 18 cm sowing arrangement. These results provide some confidence that wide-row cropping could be used for the management of difficult to control weeds with inter-row herbicide application without compromising crop yield and profitability. However, further research is required to determine yield responses in growing seasons with average to above average rainfall.

References

Blackwell P, Porrier S and Bowden B (2006). Response to winter drought by wheat on shallow soil with low seeding rate and wide row spacing. Agribusiness Crop Updates, Perth February 2006, Farming Systems Updates pp 57-61. http://www.agric.wa.gov.au/pls/portal30/docs/FOLDER/IKMP/FCP/FarmingSystems2006_3.pdf. Accessed 17 April 2008.

Belford RK and Riethmuller GP (1992). Narrow row spacings have little effect on yield of wheat in the eastern wheatbelt. Western Australian Department of Agriculture Division of Plant Industries Technical Report No. 51, May 1992, 13 pp.

Burch RN (1986). Final report: Effects of changing row spacings of wheat yields. Wheat Research Council Project No. 498/0051. Western Australian State Wheat Research Committee Project No. 355/0067, 22 pp.

Felton WL, Marcellos H and Murison RD (1996). The effect of row spacing and seeding rate on chickpea yield in northern New South Wales. Proceedings of the 8th Australian Agronomy Conference, Ed Mohammad Asghar, pp. 250-253. Toowoomba. The Australian Society of Agronomy. http://www.regional.org.au/au/asa/1996/contributed/251felton.htm . Accessed 17 April 2008

French RJ and Harries M (2006). A role for wide rows in lupin cultivation in Western Australia. Proceedings of the 13th Australian Agronomy Conference, Perth. Australian Society of Agronomy. http://www.regional.org.au/au/asa/2006/concurrent/systems/4557_frenchrj.htm . Accessed 17 April 2008.

Hashem A, Fulwood R and Collins M (2005). Weed control by banding and inter-row spraying of herbicides in wide row lupins. Agribusiness Crop Updates, Perth February 2005, Weed Updates pp 23-25. http://www.agric.wa.gov.au/pls/portal30/docs/FOLDER/IKMP/FCP/WEEDSUPDATEEXTENDED.PDF Accessed 17 April 2008

Unger PW, Stewart BA, Parr JF and Singh RP (1991). Crop residue management and tillage methods for conserving soil water in semi-arid regions. Soil & Tillage Res. 20:219-240.

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