Erol Oral

Document Type

Thesis - Open Access

Award Date


Degree Name

Master of Science (MS)


Plant Science


The reason for undertaking this research was to determine the effect of plant spacing on soybeans in South Dakota. It has been estimated that the average soybean yield could be raised 7 to 10 bushels per acre by using improved varieties, controlling weeds, planting as early as possible, practicing good soil and crop management, selecting the proper row spacing and plant population and using improved cultural practices. Specific research objectives were: (1) to study soy bean growth, yield and other plant characteristics with different plant spacings and plant populations, (2) to determine the differences between narrow and wide row spacings at different plant populations and (3) to measure the effects of plant and row spacing on yield potential under South Dakota conditions. Although the soybean has not been the subject of very extensive genetics research, plant characteristics and cultural principles of production have long been studied by agricultural workers interested in soybean production. Soybeans were first grown as a forage crop. Caviness indicates that soybeans were introduced into this country with production methods similar to other row crops. The width between rows was maintained at 24 to 36 inches in 1922. When soybeans first came into the corn belt in the 1930 's, Illinois agronomists showed that optimum yields were obtained from narrow row spacing. Due to the ease with which soybeans could be planted and cultivated with corn equipment, however, most farmers still used 40-inch row spacing. In 1958, Pendleton, Bernard and Hadley decided to take another look at narrow row culture. They indicated that an advantage for 24-inch rows over 40 inch rows occurred on three Agronomy Research centers located in Illinois. In recent years the effect of plant spacing on soybean yield has been the subject of many investigations. Research showed that close planting ensures better emergence in crusted soil, provides more competition for weeds and compensates for mechanical losses caused by tillage equipment. Study of published product ion and research data shows that many things have to be included. The effect of plant spacing of soybeans on yield, the indirect influence of plant characters and effects on the soil have to be taken into consideration. Our objective in this research has been to study and measure relative advantages of narrow versus standard spacing in South Dakota. We studied plant spacing, population, plant characteristics, plant height, canopy width, maturity, lowest pod height, number of sterile nodes, branching, number of seeds per plant, seeds per pod, seed size, ground coverage, oil and protein contents and yield. Plant characteristics and seed yields were also evaluated by study of correlation between each of several factors and yield.

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South Dakota State University