Mineral nutrition of developing soybean seedlings: A greenhouse investigation with nutrient solutions and sand medium

Although soybean seeds generally contain adequate amounts of most nutrients for early seedling growth and development, they are often low in certain nutrients. We hypothesize that such deficiencies adversely affect seed germination and early seedling development, and that supplying the deficient nutrients enhances germination and seedling development;The major objectives of this study were to investigate: (1) the quantitative and qualitative relationships among various nutrient solutions and developing soybean seedlings; (2) the effects of these solutions on the accumulation or loss of dry weights and nutrients in roots, shoots, and cotyledons; (3) which nutrients are more crucial for the early development of soybean seedlings; and (4) the period during which these nutrients are needed most;The study, conducted under greenhouse conditions, consisted of seven experiments. Each experiment was arranged in a replicated randomized block design. Soybeans were grown in acid-washed sand in plastic cups. Treatments included a factorial combination of Ca and Mn in deionized water, and factorial deletions of Ca and Mn from Hoagland Solution;The seedlings were sampled at the pre-emergence, emergence, unifoliate, and second trifoliate stages which occurred at 1, 7, 12, and 19 days after planting, respectively. Plants were partitioned into roots, shoots, and cotyledons; each portion was weighed and analyzed for P, K, Ca, Mg, Mn, B, Fe, Cu, Al, and Zn;Dry weights of cotyledons decreased irrespective of treatment; conversely, increases in dry weights of roots and shoots varied due to Ca (primarily) and Mn treatments; other nutrients had little influence on seedling growth. If only Ca and Mn in water were supplied, root weight was larger than shoot weight; in Hoagland Solution, root and shoot weights were similar;Depletion of most nutrients from the cotyledons occurred. However, the low Ca depletion, along with a decline in cotyledon dry weight, increased Ca concentration in the cotyledons. The contents of any one nutrient in roots and shoots were influenced by its presence or absence in solution and was modified by the presence of Ca and Mn. The shoots generally had higher nutrient contents than the roots. Differences in nutrient contents were related to differences in dry weights