Neubauer seedling technique to determine availability of nutrient elements for wheat from selected South African soils

Abstract

The quantity of plant nutrient elements removed from soil by wheat (Triticum aestivum) seedlings were compared with the results of soil tests. Four soils were selected to represent the major parent material and climatic factors responsible for the formation of important agricultural soils in the central eastern Cape Province of South Africa. Acid‐washed sand was used as control. Seedlings were grown for 21 days and nutrient element content in both plant material and soil were determined. Soils derived from dolerite rocks had significantly (P<0.05) higher calcium (Ca), magnesium (Mg), potassium (K), sodium (Na), and phosphorus (P) than those derived from sedimentary rocks. However, iron (Fe), manganese (Mn), and copper (Cu) were higher in soils derived from sedimentary rocks compared to those from dolerite rocks. The differences are attributed to elemental composition of minerals in the two parent rock materials. Within each rock group, soils derived from sites with higher temperature and low rainfall (semi‐arid climate) had significantly (p<0.05) higher nutrient element content than those from sites with lower temperatures and higher rainfall (humid climate). As far as plant growth is concerned, all the soils were well supplied with Ca, Mg, K, Na, and zinc (Zn), but were deficient in P, Fe, and Mn. The trend in uptake of soil nutrient elements by wheat seedlings mirrored their concentration in the soils. Estimates of plant‐available nutrient elements as determined by soil tests and their uptake as determined by tissue concentration were highly correlated for some nutrient elements (r²=0.83, 0.79, 0.94, 0.54, 0.69, and 0.61 for Ca, Mg, K, P, Na, and Zn, respectively) and weak for others (r²=0.47, 0.35, and 0.37 for Fe, Mn, and Cu, respectively). Notwithstanding the shortcomings of extrapolating pot derived results to field conditions, it is concluded that the Neubauer technique may offer a rapid and relatively inexpensive way of relating extractable nutrient elements with plant uptake and growth. Further in country correlation studies are, however, recommended.