Row spacing effects on plant populations, canopy closure, water use, and grain yields in the brown soil zone
We compared crop performance at a 20-cm row spacing and at a 30-cm row spacing on a Swinton loam near Swift Current from 1995-98 for seeding directly into untilled wheat stubble and seeding into tilled fallow. The results show that, in the water-limited environment, grain yields and water use efficiencies (WUE) at the 30-cm row spacing were generally lower than at 20-cm spacing. Flax, lentil, and spring wheat had yields and WUE were between 10 and 20% lower at the 30- compared with the 20-cm row spacing. Durum and desi chickpea had yields and WUE about 5 to 10% lower at the 30-cm row spacing. For field pea and kabuli chickpea, yield reductions at the wider row spacing existed primarily when the seed rate was also reduced. Lowest yields with a reduced seed rate combined with wider row spacing occurred for all the pulse crops. The yields of the Brassica oilseeds (canola and mustard) were less affected by row spacing than other crops. For all crops except chickpea, there was a lower plant density at 30- compared with 20-cm row spacing. However, for pulse crops and cereals, since two seed rates were used in this study, we were able to show that the lower yields for the wider row spacing was not due primarily to lower plant densities. We attributed the higher grains yields and WUE at the 20-cm row spacing compared with 30-cm row spacing to more efficient use of water due to quicker exploitation of the soil between the seed row soil and reduced loss of soil water from evaporation in the soil between the rows due to a more quickly closed canopy. Hence, the yield effects of row spacing are primarily related to efficient water use so the yield reductions from widening row spacing appear to be more pronounced in the Brown soil zone than in the Black soil zone. Producers in the Brown and drier parts of the Dark Brown soil zones should consider carefully both the disadvantages and advantages of widening the row spacing on their seeding implement.
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