Submitted to: Subtropical Plant Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 14, 1998
Publication Date: N/A
Interpretive Summary: Conservation tillage (CT) systems are used to reduce wind-blown soil erosion, improve soil quality, and reduce soil moisture loss between plantings. Vegetable crops are traditionally grown in soil which has been stirred up by plowing and cultivating. Direct-seeded winter broccoli was used to evaluate three tillage systems, conventional tillage, minimal tillage (MT), and no tillage (NT), in a semi-arid environment over three seasons. Marketable yields and floret mineral nutrients were similar from broccoli grown under all tillage systems. By the third year, soil nutrients were both higher in the upper foot of soil and tended to accumulate more towards the surface in the conservation tillage systems. Sodium salt levels were reduced by CT. The amount of weed seeds per unit of soil was higher in NT soils, particularly near the surface.
Technical Abstract: Winter broccoli (Brassica oleracea, L. Botrytis Group) production was evaluated under three tillage systems, conventional (CVT), minimum tillage (MT), and no-till (NT), which were established in August 1994. After three growing seasons, marketable yields were similar among tillage systems, but plant densities at harvest were lower in the NT system compared to the CVT-grown broccoli plants. NT-grown broccoli heads compensated for stand differences by producing slightly larger heads (P=0.17). The percentage of marketable yield at the first harvest relative to the total yield was not affected by tillage practice. Floret NO3, chlorophyll, and carotenoid concentrations were reduced when grown by conservation tillage. At the end of the third growing season, the amount of germinable seeds in the upper 0-5 cm of soil was highest in the NT soil. Total plant weed populations were higher in conservation tilled soil. Total N, K, and Mg concentrations in the upper 30 cm soil profile were highest in the NT system. Total C an N, K, Mg, and P nutrient gradients were greatest in NT soil. Upper soil profile Na levels were highest in soils subjected to CVT. MT responses were generally intermediate to those of CVT and NT.