Frost at anthesis of wheat reduces grain set. Characteristics of frost in a large section of the wheat belt of one Australian state (N.S.W.) are described. Using cluster analysis, the region can be divided into four homogeneous areas according to five general characteristics of frost. These characteristics are the mean Julian day of first and last frost, the mean number of frost days, the proportion of single-day frosts (days on which a frost did not occur on the following day) from August to October and the proportion of frost free periods from August to October of less than 5 days' duration.All these characteristics were found to,be closely related to altitude in all areas, but not to latitude or longitude. Within each area, regression equations were developed which explained at least 87% of the variation in four of the general characteristics. Thus, altitude appears to be a useful predictor for these characteristics.The validity of each equation was tested using three independent data sets. The mean percentage errors for the mean Julian day of first and last frost and the proportion of single-day frosts from August to October were 5, 5 and 8% respectively. Errors for the mean number of frost days and proportion of frost free periods from August to October of less than 5 days duration were approximately 7% for one site and approximately 20% for two other sites.The characteristics of frost in the period in which most winter crops flower are also described. The characteristics are the mean date of last heavy frost and last frost, and frost spells in each of August, September and October. In order to minimize risk from frost during anthesis and from high temperature and water stress during grain filling, this analysis suggests that anthesis should occur in earlylmid September, late Septemberlearly October and earlylmid October for the western, central and eastern parts of the region respectively. For areas in the north-eastern and south-eastern parts that are above 500 m, anthesis should occur mid/late October and earlylmid November respectively. These analytical findings are consistent with field studies on wheat.A weak negative correlation between the first and the last frost is present in most of the sites of the region. This suggests that if in any particular year the first frost occurs earlier than its long-term mean, then the last frost tends to occur later than its long-term mean.
Fruit of peanut (Arachis hypogaea L.) and burrs of subterranean clover (Trifolium subterraneaum L.) were shown to develop in white siliceous sand which was low in boron. Fruit and seed production and yield did not vary with the boron nutrition given to the medium in which seeds developed. The results suggest that for the development of their fruits, peanut and subterranean clover translocate boron in their phloem.
Rainfall is an important variable in the wheat production areas of Australia. This analysis examines, firstly, the pattern of rainfall over 2.3 million ha of a high-quality wheat-producing region, and secondly, develops regression equations for rainfall prediction over this region. Most of the variation in rainfall pattern across the region is accounted for by differences in October-to-March (summer) rainfall and in April-to-September (winter) rainfall. The summer rainfall differences account for over two thirds of the variation. Based on these two rainfall periods, a partitioning of the study area reveals five distinct regions. The second part of the analysis uses multiple regression to provide a set of equations for rainfall prediction at any location in the region, for a number of rainfall periods. These equations use altitude, longitude and latitude as predictors. Nearly all of the equations explain between 80% and 94% of the variation in rainfall. Differences between regions are accounted for in the analysis, making the equations widely applicable. The validity of the mean rainfall equations was tested on three further sites: the mean prediction error was 6.9%. This approach may be applicable where large land masses with similar geographical features occur.
Dry matter accumulation in maize, hybrid pennisetum and mid- and late-season pearl millet were assessed following planting in mid-summer at Camden, New South Wales. Productivity was high in maize and hybrid pennisetum, the maximum above-ground rate of dry matter accumulation averaging 590 kg ha-1 day-1 for 20 days for maize in March 1975. Productivity was lower in the pearl millets which lodged in April of 1975 and 1976. Organic matter digestibility was superior in maize, phosphorus concentrations were higher in hybrid pennisetum and magnesium and calcium concentrations were the same in hybrid pennisetum as in maize. The concentrations of minerals would be generally too low to maintain highly-productive livestock if they were fed exclusively on these tropical forages.
Transport and distribution patterns of manganese were studied in soybeans (cultivars Lee and Bragg) grown over a wide range of manganese supply levels in solution culture. Increasing the manganese supply from 1.8 �M to 450 .�M produced symptoms of manganese toxicity and reduced growth in both cultivars. Symptoms and dry matter yield reductions were more severe in Bragg. Manganese taken up by the plant was preferentially transported to young expanding tissue, while the amount moving to older tissue, including cotyledons, increased with availability. At high manganese supply the leaves accumulated higher concentrations with age, resulting in a decreasing concentration gradient between old and young leaves. There was no difference between Lee and Bragg in the distribution of manganese to plant parts or in the concentration of manganese in actively growing tissue. Manganese deficiency symptoms developed on both cultivars grown under limiting supply conditions. Partial mobility of the element was indicated: small amounts were translocated from the old leaves when young expanding leaves were manganese deficient. Nevertheless, considerable amounts remained in the cotyledons, and manganese appeared to have a low mobility when the plant's supply was limited.
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