A Study to Look at Practices Aimed at Reducing Mechanical Cultivation in Organic Corn Production

View the project final report

• 2008 annual report

Commodities

• Agronomic: general grain crops

Practices

• Production Systems: general crop production

Weed control is one of the greatest challenges in organic row crop production. Cultivation is time, labor and energy intensive. In labor short situations it competes with labor needed for first hay crop harvest, having a profound effect on the productivity and profitability of the cropping system. This study seeks answer to: 1. What effect does each cultivation pass have on corn plant population in an organic crop production? 2. Can narrow row corn reduce the need for mechanical cultivation and if so what spacing provides the best weed control from early canopying of the crop? 3. Will inter-seeding a cover crop into organic corn at the time of final cultivation provide enough ground cover to compete with weed populations without reducing yield? The study will be established using a randomized complete block design, with field-scale plot sizes at 2 farm sites. The main plot treatment will consist of 2 row spacings, 15” and 30”, with sub-plot treatments comparing 2 cover crop species mixes (clover and clover/grass). Extensive outreach is planned to disseminate the results of this project.

Plant population and row spacing recommendations have been well researched and established for conventional corn production. The genetics of current conventional hybrids generally tolerate heavier populations. The corn varieties available in organic production are more limited and may not have the same tolerance to plant crowding. Currently organic farmers follow the population recommendations for conventional hybrids since published plant population comparisons under organic management in corn are virtually non-existent.

In order to look at the relationship of population thinning during flex-tine harrowing and yield, this study proposes to observe and record the impacts of flextine harrow cultivation on final populations, weed control and impacts on yield at three row spacings; 6, 15 and 30 inches. The corn will be planted at 36,000 seeds/Ac with a targeted harvest population of about 32,000 plants/Ac. Population counts will be taken after each pass of the flex-tine harrow. Final population counts will be taken and correlated with harvested yields. The corn with 6” row spacing will be established with an Aitchison no-till drill. A corn planter set for 30” rows will be used for both the 15 and 30” spacings. The planter will double back to place the corn in 15” rows.

Under organic management, narrow row corn offers several potential advantages to the production system, including better weed control and a reduction in soil erosion, both from earlier canopy closure and improved yields from more uniform plant spacing (Agronomy Facts 52, Penn State). Early canopy closure will decrease the impact of rainfall on bare, unprotected soil and provide shading competition to germinating and young weeds. More uniform or equidistant plant spacing should reduce intra-plant competition for nutrients and soil moisture. Purdue researchers reported a 2.7% yield increase in corn grain yield in 15” rows compared to 30” rows (Nielsen, 1997). Michigan researchers reported a 4% yield increase (Widdecombe and Thelen, 2002). Yield responses are not reliable from year to year. Nielson (1997) reports that yield responses varied from a –3% to + 8% over 9 year-location environments.

Many studies looking at the effects of row spacing, particularly narrow row corn on weed management include some level of herbicides even when cultivation is included as a treatment (Boerboom, 2007). Similar research strictly under organic corn production is very limited. This project would contribute to the information base of row spacing effect on weed populations and competitiveness.

Living Mulches and cover crops have been evaluated for their weed suppressive effects.
This study will establish 2 different cover crops as a sub-treatment in blocks across the rows to evaluate weed suppressive benefits. Zemenchik, Albrecht, Boerboom, and Lauer (2000) concluded after a 2-year study looking at corn production with Kura clover as a living mulch that, “Kura clover can be managed as a living mulch in corn with little or no corn whole-plant or grain yield reduction and clover will recover to full production within 12 mo without replanting.” Experiments with Kura clover establishment in NY State have been unsuccessful (personal experience), but we are interested in looking at clover species.

Singer and Pedersen (2005) established corn in 3 legume species cover crops. After planting, the cover crops were suppressed by mowing or burning. In this experiment we will try to garner the weed suppressive effects of a living mulch by seeding our inter-row species at the time of the last cultivation. We will compare 4 cover crop options as sub plots over the 2 main treatments of row spacing; berseem clover, red grazing type clover, annual ryegrass and a red grazing clover/ryegrass mix.