Responses to precision planting in canola and grain legume crops

Context

Sowing with conventional airseeders and seed drills results in random placement of seed along the row, causing variable interplant competition. Precision planting improves the uniformity of seed placement, minimising interplant competition, with the potential to improve yields. While precision planting has been used widely in summer cropping its benefits to yield in winter crops has not been well documented.

Objectives

Our hypothesis was that precision planting will improve yields by reducing the degree of interplant competition in crop stands. The objectives of the work were to (a) quantify the benefits to yield of improvements in uniformity in plant spacing in canola and some grain legume crops, (b) examine how crop stand uniformity affects responses to variation in plant density and (c) identify the stage of development which are most sensitive to improvements in interplant competition.

Methods

Twenty field experiments were conducted with canola (11 experiments) and different grain legume crops (nine experiments) over three years in southern and western Australia. In each experiment crops were sown at between three and six densities with either a conventional seeder or a precision planter. Crop establishment, variation in interplant distance, crop biomass, grain yield and yield components were measured. Analyses of responses in biomass and yield per plant were also used to assess effects on interplant competition.

Results

Precision planting did not improve seedling establishment but consistently improved stand uniformity. Yields were increased by precision planting in 11 experiments, with greater effects observed in canola. In the remaining experiments, yields were similar. Average yield benefits were 6 % in canola, 2 % in lentil, 9 % in faba bean and 13 % in a single experiment with lupin, which represented average yield increases 80–100 kg/ha with maximum increases of 300 kg/ha in canola and 600 kg/ha in faba bean. Increases in yield from precision planting were related to improvements in growth after flowering and early podding and were influenced by rainfall in spring. Canola showed less variation in yield to variation in plant density than grain legumes. Responses to plant density in growth per plant suggested precision planting improved a plant’s ability to use available space, resulting in a higher yield at the same density compared to conventionally-sown crops.

Conclusion

Precision planting increased crop stand uniformity and has the potential to improve yields of dryland winter crops, but results are seasonally-dependent.

Implications

The work highlighted the value of improved crop stand uniformity to yield independently of variation in crop establishment. It provides evidence that precision planting has the potential to improve yields of canola and some grain legumes in dryland farming systems, but the environmental conditions under which the greatest benefit will be achieved need to be defined.