Chain diker effects on seeded grass establishment following disk chaining.

Placing basins in rangeland seedbeds to capture rainfall has enhanced seeded grass establishment, but it has not been practical on debris-littered land following rootplowing for brush control. A disk chain tested previously will traverse land littered with debris or shrubs while tilling the soil for seedbed preparation. A chain diker is an implement designed to form 10-cm deep basins with a volume of 3.9 +/- 0.9 liters on tilled land. Combining the 2 implements provided tillage, land smoothing and basin formation in the soil with a single pass on debris littered land. Our 4-year study compared established grass densities on disk-chained seedbeds with and without chain diking at 5 locations in west Texas where land was rootplowed for honey mesquite (Prosopis glandulosa Torr. var. glandulosa) control. At 4 locations seedbeds were aerially seeded with 2 kg ha(-1) pure live seed (PLS) of WW Spar bluestem (Bothriochloa ischaemum (L.) Keng). At 1 location a mixture of 6 grasses, including Spar bluestem, was aerially seeded at 2.8 kg ha(-1) PLS. Evaluations were based on established grass densities at the end of the first growing season. At 3 locations, a seeding-before-diking treatment was included to simulate seed dropping from a seedbox mounted over the disk-chain's roller. In the Rolling Plains region of northwest Texas (4 sites), when growing-season rainfall was less than 400 mm, chain-diked seedbeds increased grass densities 2.6 times (P = 0.05) compared to non-diked seedbeds. When growing-season rainfall was greater than 500 mm, grass densities on diked seedbeds were similar to non-diked seedbeds. In the Trans-Pecos region of far-west Texas (1 site), where average growing-season rainfall is 337 mm, diked seedbeds produced 33% greater grass densities (P = 0.05) than non-diked seedbeds with rainfall of 552 mm. Densities of kleingrass (Panicum coloratum L.) and Spar bluestem were significantly greater in the diked seedbeds compared to non-diked seedbeds, and the other 4 grasses were not significantly influenced by seedbed methods. Grass densities were similar whether seeding after diking or before diking. Since long-term, growing-season rainfall has averaged below 500 mm between 65% to 87% of the time at these locations, our data suggests that it would be advantageous to include chain diking in combination with disk chaining for grass establishment on rootplowed land littered with brush debris. DOI:10.2458/azu_jrm_v54i2_wiedemann