Nutrient uptake and distribution by bread and durum wheat under drought conditions in South Australia

An important limitation to the production of durum wheat in South Australia is its poor adaptation to the alkaline, sodic soils of the cereal belt, wh ich often results in nutrient imbalances in the crop. A field experiment wa s conducted at Palmer, South Australia, to measure the nutrient uptake and distribution between grain and straw of 3 bread wheat cultivars and 9 culti vars and breeding lines of durum wheat. The purpose of the work was to char acterise the patterns of nutrient uptake and to examine whether there were major, consistent differences between bread wheat and durum wheat. Rainfall during the growing season was below average and the crops suffered from dr ought stress after anthesis. Plants were marginally deficient or deficient in nitrogen (N), phosphorus ( P) and zinc (Zn), and boron (B) concentrations were high. Compared with bre ad wheat, durum wheat had a very much higher concentration of sodium (Na), higher concentrations of calcium (Ca) and sulfur (S), but lower concentrati ons of potassium (K), magnesium (Mg), manganese (Mn) and copper (Cu). Total amounts of P, Zn and Na in the shoot continued to increase throughout the growing season with significant increases occurring during grain filling, w hereas there was little increase in the amount of N, K, B and Mn during gra in filling. The maximum rate of nutrient uptake occurred before the time of maximum crop growth rate, and was in the order K (10.1 weeks after sowing) , N (10.6), P (11.3), Mn (12.0), Zn (12.5) and B (14.6); maximum growth rat e occurred at 14.8 weeks. There was no consistent difference between bread and durum wheat in the partitioning of nutrients to the grain. The importance of N and Zn uptake to the growth of the durum wheat genotype s was shown by significant correlations between maximum uptake rates of the se nutrients and maximum crop growth rate, with the strongest correlation b eing with Zn. Growth rate was not correlated with uptake rates of other nut rients. A number of genotypes of durum wheat had maximum rates of Zn and Mn accumulation up to twice those of the current commercial genotypes. Some o f these lines have yielded well at Zn- and Mn-deficient sites which indicat es that the micronutrient efficiency of durum can be improved. Late in the season the experiment showed signs of infection by crown rot (F usarium graminearum Schw. Group 1). Durum wheat showed more severe symptoms than bread wheat and the number of white heads in durum wheat was inversel y correlated with the concentration of Zn in the shoot during the pre-anthe sis period.