DISTRIBUTION AND REDISTRIBUTION OF MINERAL NUTRIENTS AND DRY-MATTER IN GRAIN-SORGHUM AS AFFECTED BY SOIL-SALINITY

A study was made of the effects of soil salinity on dry matter product ion, grain yield, and the uptake, distribution and redistribution of m ineral nutrients in irrigated grain sorghum. Soil salinity (EC, 3.6 mS /cm) reduced seedling establishment by 77%, and dry matter and grain y ields per plant by 32%; grain yield/ha was reduced by 84%. Salinity re duced grain number per head, but not individual grain size. The accumu lation of dry matter and most nutrients was reduced by salinity, but t he distribution and redistribution of nutrients within the plant were largely unaffected. Redistributed dry matter provided 52 and 31% of th e grain dry matter for control and salt-affected plants, respectively. Salt-affected plants had a greater proportion of their sulfur (S), ma gnesium (Mg), sodium (Na), and chloride (Cl) in stems and leaves than control plants at maturity. Grain had 50-90% of the nitrogen (N), phos phorus (P), S, and Mg, 20-50% of the potassium (K), manganese (Mn), zi nc (Zn), and copper (Cu), but < 20% of the calcium (Ca), Na, Cl, and i ron (Fe) contents of the whole plant. Over 65% of the N and P, and fro m 20 to 30% of the K, S, Mg, Cu, and Zn was redistributed from the ste m and leaves to grain. There was no redistribution of Ca, Na, Cl, Fe, and Mn. Leaves were more important than the stem as a source of redist ributed N, but the leaves and stem were equally important as sources o f redistributed P, K, S, Mg, and Cu. Redistribution from the stem and leaves provided 80% of the K and 20-50% of the N, P, S, Mg, Zn, and Cu accumulated by grain. Concentrations of Na, and especially Cl, were h igh in vegetative organs of salt-affected plants, but not in grain. It was concluded that although moderate salinity was detrimental to the establishment and yield of grain sorghum, it had little effect on patt erns of distribution and extents of redistribution of mineral nutrient s.