In the Nebraska Sandhills region (central USA), crop cultivation under center-pivot irrigation was widespread during the 1970’s. Many marginal sites have subsequently been abandoned, leaving large areas of exposed sandy soils. Revegetation is needed to prevent further erosion and expansion of these areas. This experiment, undertaken in Custer County, assessed the effects of tillage, irrigation level, seed coating and species (four native perennial bunchgrasses) on grass establishment.
On abandoned cropland, tillage treatment comprised plots shallow disked a day prior to seeding, or untilled (forage sorghum stubble residue remaining). Irrigation (in tilled and untilled sub-plots; 2 replications) comprised water applied in three equal amounts (15-17 July, 21-22 July, and 27-29 July, application dates based on moisture stress) in 60 m width circular bands at a total of 0, 2 or 4 cm of water.
From 11-13 May 1982, seven hand broadcast seeding treatments (24 replicates each) were applied in 18 m² sub-sub plots of the tillage by irrigation treatments: sand bluestem Andropogon gerardii var. paucipilus (hand broadcast at 32-39 seeds/m²) and little bluestem Schizachyrium scoparium (at 72-116 seeds/m²) seeds coated with a lime and nutrient slurry at three rates (heavy, light or zero).
A seed mix of non-coated switchgrass Panicum virgatum (27 seeds/m²) and sand lovegrass Eragrostis trichodes (18 seeds/m²) was also broadcast.
Seedling density was measured on 24-25 September 1982, 7 June 1983 and 15 August 1983.
Seedling establishment was consistently higher for all seeded species on the disked than non-disked areas in all sampling periods (establishment percent of seeds - disked: September 1982 - 6.0%, June 1983 - 5.0%, August 1983 - 5.1%; untilled: September 1982 - 3.8%, June 1983 - 3.3%, August 1983 - 3.6%).
Whilst the amount of water applied was only a small proportion of that available during the growing season (precipitation in the 1982 growing season was 36 cm), establishment increased as irrigation increased; a linear response occurred indicating that timing of irrigation (at peaks of water stress) was important.
At each sampling period, establishment of sand bluestem (4.8., 4.2 and 4.2%) and little bluestem (5.5, 4.3 and 4.4%) was similar. Establishment of the switchgrass-sand lovegrass mixture was a little less (3.3, 3.2 and 3.3%).
Seed coating had no influence on establishment being washed off soon after sowing by rain, thus any effect it may have had on survival was lost.