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United States Department of Agriculture

Agricultural Research Service

Research Project: OBJECT MODELING AND SCALING OF LANDSCAPE PROCESSES AND CONSERVATION EFFECTS IN AGRICULTURAL SYSTEMS Title: Relationships between sunflower plant spacing and yield: Importance of uniformity in spacing

Authors
item McMaster, Gregory
item Buchleiter, Gerald
item Bausch, Walter

Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 25, 2011
Publication Date: January 5, 2012
Citation: Mcmaster, G.S., Buchleiter, G.W., Bausch, W.C. 2012. Relationships between sunflower plant spacing and yield: Importance of uniformity in spacing. Crop Science. 52:309-319.

Interpretive Summary: Growing sunflower (Helianthus annus L.) in semi-arid regions often has poor seedling emergence and patchy stands, leading to lower yield. Our hypothesis was that plant spacing was positively related to individual plant yield, and this relationship would strengthen as water deficits increased. In a 2-yr study in northeastern Colorado, individual plant spacing within rows, and the associated final grain yield, was measured for different irrigation treatments. Despite high variation, highly significant positive linear and polynomial regressions were found for plant spacing and plant yield (P < 0.001) for all irrigation treatments in both years. However, given the high variation individual plant yield with spacing, regression explained no more than 22% of the variation. No consistent pattern in linear regression slope, y-intercept, or R2 values among irrigation treatments were noted, thereby not supporting the expectation that the relationship would be greater as water deficits increased. Further analysis showed similar results as the regression equations, but indicated plant spacing explained more of individual plant yield than irrigation treatment. Implications of these results suggest there is a cost to final yield per acre, where large spacing results in lower yields, even though these plants have the highest yields per plant of any spacing classes. Machinery and seedbed preparation leading to more uniform plant spacing likely will improve yield.

Technical Abstract: Sunflower (Helianthus annus L.) production systems in semi-arid regions often have difficulties in seedling emergence and patchy stands, leading to lower yield. Our hypothesis was that plant spacing was positively related to individual plant yield, and this relationship would strengthen as water deficits increased. In a 2-yr study in northeastern Colorado, individual plant spacing within rows, and the associated final grain yield, was measured for different irrigation treatments. Despite high variation, highly significant positive least squares linear and second-order polynomial regressions within-row spacing and plant yield (P < 0.001) were observed for all irrigation treatments in both years. However, given the high variation individual plant yield with spacing, regression explained no more than 22% of the variation. No consistent pattern in linear regression slope, y-intercept, or R2 values among irrigation treatments were noted, thereby not supporting the expectation that the relationship would be greater as water deficits increased. Leverage plots showed similar results as the regression equations, but indicated plant spacing explained more of yield than irrigation treatment.Regression tree analysis further confirmed that plant spacing was more important than irrigation treatment in explaining final plant yield. Implications of these results suggest there is a cost to final yield per unit area, where large spacing results in lower yields, even though these plants have the highest yields per plant of any spacing classes.

Last Modified: 12/19/2014