INTERIM EVALUATION OF PHOSPHOGYPSUM AS AN AMELIORANT FOR SOIL ACIDITY IN SUGARCANE
Results are reported of a 3x3x3 factorial trial in which phosphogypsum (PG), dolomitic limestone (DL) and single superphosphate (SS)were applied to sugarcane. The trial was situated on a Kranskop form soil with a moderately toxic aluminium (AI) content. Based on the combined yield responses from the plant and first ratoon crops, treatments with SS were superior to those with PG, and little response was obtained from DL. The high P in-furrow treatment (90 kg P/ha) gave a highly significant response of 3 t/ha sucrose compared with 2,1 t/ha from the best PG treatment (5 t/ ha). Leaf P and Ca also increased with both PG and SS application. Chemical changes in the soil following PG application resulted in considerable leaching of Mg below the 400 mm soil depth. Improved chemical changes included increased pH and Ca levels in the subsoil together with a reduction in exchangeable AI. The SS/PG interaction, evidence from third leaf P analyses, and lack of any marked response to liming coupled with good root development to depth indicated that yield response to PG was due mainly to its P content. Enhanced Ca content and diminished acid saturation in the subsoil may be beneficial.
CALCIUM DEFICIENCY IN CLAYEY B HORIZONS OF SAVANNA OXISOLS
The restriction of crop root growth in Cerrado (savanna) Oxisols often reduces yields because the volume of soil explored by the roots is insufficient to supply enough water during dry periods that occur in the rainy season. A recent soil survey of the 580 000 hectares of the Federal District in Central Brazil shows a number of profiles that have clayey B21 horizons within 50 centimeters of the surface with very low levels of exchangeable calcium + magnesium (0.2 milliequivalents per 100 grams or less) and no exchangeable aluminum. The hypothesis that root penetration in such subsoils is limited by lack of calcium, rather than by aluminum toxicity, is supported by the results of simple and inexpensive tests showing that the addition of 0.10 to 0.15 meq/100 g calcium as chloride, phosphate, or carbonate effectively normalized seedling root growth, which, in the absence of such additions, stopped within a few days. The addition of magnesium carbonate, however, did not improve root growth. To test whether the leaching of calcium salts might ameliorate the calcium deficiency in the subsoil, samples were taken from an experiment that had received about 2500 kg/ha calcium as limestone and ordinary superphosphate at installation 2 years previous. Compared with root growth in samples from adjacent virgin soil, these soils showed improved root growth to as deep as 75 cm, thus suggesting that fertilizer management can have a beneficial effect on subsoil rooting in such soils.
Effects of Storage Temperature and Duration on Bioactive Concentrations in the Seed and Oil of Brassica napus (Canola)
The effects of storage temperature and duration on phytosterol, tocopherol and carotenoid concentrations are assessed in canola seed, and oil extracted using two different techniques, over a 10 month period. Increases to oxidation indices (K232, K270 and ΔK) are observed in the solvent extracted oils, and in the seed stored at 40 °C, indicating the formation of primary and secondary oxidation products. Only small decreases in the concentrations of γ-tocopherol and β-carotene are observed across the 10 month period. Phytosterol concentration decreases over time, with similar degradation rates observed in both seed and oils. α-tocopherol and lutein are well preserved up to 7 months in all samples, despite oil oxidation, and further research will be needed to identify the cause for retention of bioactives. The results indicate that in order to preserve phytosterols, tocopherols and carotenoids in seed stored in bulk for extended periods, storage temperatures should remain at or below 21 °C. Moreover, oil stored at 4 °C or −18 °C, results in high bioactive concentrations and slows the onset of oil oxidation, compared to oil stored at room temperature. 
 
Practical Applications: Industrial storage conditions have been shown to greatly influence the chemical processes that occur with canola seed and oil. However, the effects of typical storage conditions on phytosterols, tocopherols and carotenoids in canola seed and extracted oil, are not yet known. This study presents the effects of typical seed and oil storage conditions on phytosterol, tocopherol and carotenoid concentrations, whilst monitoring oxidation indices and FFA, and thus provides information to seed handlers and oil processors on storage conditions that may preserve these bioactives. Moreover, the different behaviours of bioactives are examined relative to the oil extraction technique used, and present opportunities to optimise oil extraction techniques. 
 
 
 
Time series plots for α-tocopherol concentrations in canola oil stored at different temperatures over 280 days, illustrating a difference in behaviour between the solvent extracted oil and the hand-press extracted oil.