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The use of crop rotation in the Eastern Free State to enhance profitability and reduce financial risk related to mono-cropped maize and wheat, has rekindled this research. The aim of this research was firstly to quantify the effect of dry bean, lupin, sunflower and fallow on the yield of a subsequent wheat crop arid secondly, to quantify the effect of soyabean and wheat on the yield of maize. Wheat after 18 months fallow, lupin, dry bean and sunflower yielded 40, 31, 25 and 54% more than monocropped wheat. With the exception of wheat planted directly after dry bean, crop rotation reduced the variability of wheat yields. The rotational effect of sunflower on wheat appears to be unique as it simultaneously increased the yield and stability of the yield, above that of the other systems. Yield of maize grown in rotation was slightly less variable than that of the maize grown in monoculture. Crop rotation improved the protein content of maize and wheat grain, as well as the hectolitre mass of wheat.

Thirteen winter and intermediate type bread wheat cultivars were evaluated for yield stability under dryland conditions over a four year period from 1991 to 1994 and over a total of 120 environments in the Western, Central and Eastern Free State wheat producing regions of South Africa. The following statistical analyses were conducted and procedures followed to determine yield stability: (i) Shukla's procedure of stability variance(*2j); (ii) Lin and Binns cultivar performance measure (Pi); (iii) Finlay and Wilkenson's regression analysis and coefficient (b); (iv) Eberhart and Russel's deviation from regression (S2d); (v) Wricke's ecovalence (W1); (vi) AMMI model. Since the AMMI model does not make provision for a quantitative stability measure, such a measure was developed to rank genotypes. Total correspondence for significance of Spearman's rank correlation coefficients for the different analysis procedures was noted over the three production regions. No significant rank correlation coefficients were f...

Approximately 90% of the annual wheat crop produced in the Republic of South Africa is milled into flour for bread-baking purposes. The percentage of flour extracted, as well as the dough development properties, determine the milling and dough mixing characteristics. In an increasingly deregulated market environment, these quality characteristics largely determine the price of the wheat. The ability of cultivars and localities to produce high quality wheat grain must, therefore, be classified. Seven spring wheat cultivars were grown at nine localities for the period 1992 to 1995. Similar production practices were followed at all localities. AMMI (Additive Main Effects and Multiplicative Interaction) analyses were used to describe the effect of cultivar, environment and their interaction on flour extraction yield, Falling Number, gluten, as well as Mixograph dough development time, peak height and band width. Environment was found to be the most important contributor to variance for all characteristics det...

Protein content and quality determine flour quality, as well as the success of bread-baking. The stability of wheat quality characteristics is of great importance to the milling and baking industry, who have to produce an end product of acceptable and consistent quality to the consumers. It is, therefore important to classify cultivars and production regions according to their ability to produce high quality wheat grain. Seven spring wheat cultivars were grown at nine localities for the period 1992 to 1995 for the purpose of this study. The effect of cultivar, environment and their interaction on water absorption, Alveograph characteristics and loaf volume were described by AMMI (Additive Main Effects and Multiplicative Interaction) analyses. Environment was found to be by far the most important contributor to variance for all the characteristics determined. Except for water absorption, where the effect of cultivar was not significant, cultivar, environments, as well as cultivar × environment interaction,...

Preharvest sprouting significantly reduces the quality of the South African wheat crop. This study classified the preharvest sprouting resistance of 17 South African winter wheat cultivars sampled over a range of typical winter wheat growth environments. Sampling was performed under field conditions and sprouting responses were evaluated under controlled conditions. Variation in sprouting response between cultivars was predominantly genetically determined and varied from 1.7 to 7.4 on a scale from 1 (no visual sprouting) to 8 (fully sprouted). Canonical variate analysis and AMMI analysis, as well as the use of hierarchical clustering of cultivars over environments using the AMMI estimates, identified four distinct groups ranging from resistant to susceptible. The AMMI model was used as it combines the additive main effects of the analysis of variance with the interaction effects of principal components analysis. In general, Betta, and certain cultivars derived from Betta, showed good to moderate resistanc...

Changes in the genetic yield and quality potential of South African winter wheat cultivars since 1930 were investigated by means of canonical variate analysis. Yield potential improved by 87%, while test weight and protein percentage changed marginally. Flour colour improved mostly since 1965, but advancement of flour yield declined after 1984. Dough strength increased since 1930, yet current levels of dough strength should not be exceeded. When compared to farinograph assessment of dough strength, mixograph dough development time appears to be a less sensitive indicator of variation in dough strength. Selection on the basis of mixograph dough development time only, could influence a breeder's perception of the dough quality profile of his breeding programme. Protein efficiency was maintained despite improvement in yield potential. Baking quality improved by 20%. The genetic winter wheat potential advanced significantly since 1930 in meeting the increased nutritional demands of the South African population.

The inconsistent production of winter wheat with acceptable bread-making quality in the Free State reduces the commercial value of the wheat crop. In the second part of this study, canonical correlation analysis was used to determine to what extent variation of biochemical components in wheat flours was responsible for differences in bread-making quality. In addition, the effects of environmental variables such as climate, crop history and edaphic attributes on yield, rheological and biochemical traits were examined by means of canonical variate analysis. It appeared that climatic factors contributed most to variation in yield and quality characteristics. Favourable conditions during the grain-filling period improved yield and modified storage and monomeric protein ratios. Modifications under stress-related conditions, however, were not sufficient to influence mixing requirement or baking quality.

The attributes of yield and bread-making quality of winter wheats produced in the Free State are subject to environmental effects. The result is a supply to the baking industry of flour of inconsistent quality, which in turn is detrimental to the market value of wheat. Various genetic and environmental factors may affect bread-making quality. In the first part of this study we demonstrated the magnitude of environmental and genetic factors, and used principal-components analysis to examine the underlying source of variability in the bread-making quality of winter wheat cultivars. Yield and protein concentration responded to environmental influences, whereas the dough-mixing requirement was primarily inherently determined. Variation in protein concentration accounted for variation in the mixing requirement of one cultivar and the SDS sedimentation volume of most cultivars.

Small-grain stand establishment in research plots of the summer rainfall region of South Africa is a problem because of dry surface soil. A vacuum system plot planter was developed to meet these requirements. The planter has simple adjustments for changes in species, cultivars, seeding ante, row spacing, and fertilizer rate. The precision planter has fertilizer times and modified planter units. Uniform stands are achieved with most species at seeding rates varying from 5 to 100 kg ha −1 (4.5-89.0 Ib acre −1 ), with no restriction in plot length. The unit is easily transported and can plant in excess of 80 5-m (16.5 ft) plots h −1 [...]

The effect of four seed treatments and storage period of treated seed on the germination, coleoptile length and emergence of five winter wheat genotypes was investigated. The first trial was conducted under controlled conditions to determine the effect of triadimenol, terbuconazole, flutriafol + thiabendazole and carboxin + thiram-treated seed at recommended rates on the germination and coleoptile length of five genotypes, viz. Betta, Tugela, Molen, T85/21 and Karee. A second trial was conducted under field conditions to determine the percentage emergence of Betta and T85/21 treated with the same seed treatments and planted 30 mm and 60 mm deep. Significant seed treatment × genotype × storage period interactions for germination occurred. All seed treatments had an effect to varying degrees on the germination of genotypes after the nine- month storage period but not on the seed treated directly prior to germination. Significant seed treatment × genotype × storage interactions occurred for coleoptile length...