Thesis (MScAgric)--Stellenbosch University, 2019. | ENGLISH ABSTRACT: Wheat, the main cereal crop and canola, the main oilseed crop are the two most prominent crops established in the Western Cape under dryland conditions. Tine openers are most commonly used to establish these crops, but disc – and double chute openers are emerging as viable alternatives. The suitable planting depth for each opener has not yet been evaluated in the Western Cape. These openers place nitrogen (N) fertiliser at different depth in soil. Tine openers place N below the seed and disc openers mix N with seed and place it at the same depth. The double chute places N fertilser in between two twin rows of seed. The aim of the study was to determine the efficiency of establishment of wheat and canola using a tine, disc, and double chute openers, with different fertiliser placement.This study was divided into three trials, each with a specific objective: i) The first trial was conducted in a growth room to determine the effect of N rate on wheat and canola sown at different depths (1, 2, 4, and 8 cm) and in different soil types. ii) The second trial was conducted in the field to evaluate the effectiveness of a tine or disc opener to establish canola and wheat at different depths. iii) The third was another field trial to evaluate the efficiency of tine, disc, and double chute openers on wheat and canola establishment. There was no clear effect of N rate in almost all soil types for wheat and canola, but planting depth had an effect (Objective i). Most established well when sown at depths of 1 or 2 cm. Though overall canola seed establishment was poor in most soils, it is possible that the canola seeds or seedlings were damaged by coming into contact with the N fertiliser since it was previously observed that canola seeds are sensitive to N fertiliser. The tine opener planted the seed acurate at a deeper depth (Objective ii), while the disc opener planted the seed well at a shallower depth, particularly for wheat. In contrast, for canola, planting depth was not successfully controlled by either tine or disc opener. Wheat and canola seeds were affected by the N fertiliser placement (Objective iii). When the double chute and tine openers were used in placing N fertiliser, the differences were significant in comparison to when N was broadcasted or placed using the disc opener. Plant population and biomass production was determined after 30, 60, 90 and 120 days of plant emergence, while the leaf area index (LAI) was only determinedafter 30, 60 and 90 days of plant emergence. Yield was also quantified. In most cases there were no differences between broadcasted N (control) and the disc opener for plant population, biomass production and LAI; yet, there were noticeable differences to double chute and tine opener with regard to plant population, biomass production and LAI. No yield differences were observed between the various openers. | AFRIKAANSE OPSOMMING: Koring, die hoof graangewas, en canola, die hoof oliesaadgewas, is die twee meer prominente gewasse wat onder droëlandtoestande in die Wes-Kaap gevestig word. Tandoopmakers word algemeen gebruik om die gewasse te vestig, maar skyf- en dubbelsaadskut-oopmakers word toenemend beskikbaar as alternatiewe opsies. Die optimale plantdiepte vir elke oopmaker is nog nie in die Wes-Kaap evalueer nie. Die oopmakers plaas stikstof-(N)-bemesting op verskillende dieptes in die grond. Tandoopmakers plaas N onder die saad, terwyl skyfoopmakers N op die selfde diepte as saad plaas. Die dubbelsaadskut plaas N tussen twee treinspoorrytjies saad in die middel van die ry. Die doel van die studie was op die effektiwiteit van vestiging van koring en canola te bepaal, deur van tand, skyf en dubbelsaadskut-oopmakers gebruik te maak, met verskillende plasing van N. Die studie was in drie gedeeltes verdeel, elk met sy eie objektief: i) Die eerste proef was in ‘n groeikamer uitgevoer om die effek van N-peil op koring en canola wat op verskillende dieptes (1, 2, 4, en 8 cm) en in verskillende gronde gevestig is, te bepaal. ii) Die tweede proef was uigevoer onder veldtoestande om die effektiwiteit van tand en skyfoopmakers om koring en canola te vestig op verskillende dieptes te bepaal. iii) Die derde proef was ook ‘n veldproef om die effektiwiteit van tand, skyf en dubbelsaadskut oopmakers op koring en canola te bepaal, met ‘n fokus op N. Daar was geen defnitiewe effek van N-peil in byna alle grondtipes vir koring en canola nie, maar plantdiepte het wel ‘n effek gehad (objektief 1). Die meeste saad het gevestig teen dieptes van 1 of 2 cm. Alhoewel canola-vestiging oor die algemeen swak was, was dit moontlik dat canolasaailinge deur kontak met N-bemesting beskadig was. Die tandoopmaker het saad op ‘n akkurate diepte geplaas, terwyl die skyfoopmaker saad vlakker geplaas het, veral koring. Teenstaande, vir canola was plantdiepte nie suksesvol deur die tand of skyfoopmaker beheer nie. Koring en canola was wel deur N-plasing beinvloed (objektief iii).Wanneer dubbelsaadskut- en tandoopmakers gebruik was om N te plaas, was daar betekenisvolle verskille vergeleke met wanneer N breedwerpig toegedien of met ‘n skyf geplaas was. Oor die algemeen was daar geen verskille tussen N wat breedwerpig toegedien was en die skyfoopmaker i.t.v. planpopulasie, biomassaproduksie en BOI nie, alhoewel daar wel verskille tussen die dubbelsaadskut en tandoopmaker was. Geen opbrengsverskille was waargeneem nie.

Biochar can potentially increase crop production in saline soils. However, the appropriate amount of biochar that should be applied to benefit from resource preservation and increase both grain yield (GY) and quality is not clear. A pot experiment was conducted to evaluate the effects of biochar applied at various rates (i.e., 0, 5, 10, 20, 30, 40 and 50 t/ha) on the nitrogen use efficiency (NUE), GY and amino acid (AA) contents of wheat plants in saline soils. The results showed that the application of 5-20 t/ha biochar increased wheat NUE by 5.2-37.9% and thus increased wheat GY by 2.9-19.4%. However, excessive biochar applications (more than 30 t/ha) had negative effects on both the NUE and GY of wheat. Biochar had little influence on leaf soil and plant analyzer development (SPAD) values, the harvest index or yield components. The AAs were significantly affected by biochar, depending on the application rate. Among the application rates, 5-30 t/ha biochar resulted in relatively higher (by 5.2-19.1%) total AA contents. Similar trends were observed for each of the 17 essential AAs. In conclusion, the positive effects of biochar occurred when it was applied at appropriate rates, but the effects were negative when biochar was overused.

Soil aggregate instability on unprotected roadside slopes can cause landslide, soil erosion and sedimentation. Different biological and chemical soil stabilizers are used to reinforce the instable slopes. In the present study, straw mulch and Polyacrylamide (PAM) combinations were investigated on a clay soil of road cutslope in campus of Gorgan University of Agricultural Sciences and Natural Resources, Gorgan, Iran. The selected cover treatments were Polyacrylamide (2, 3 and 4 g.m-2) with wheat straw mulch (50, 150 and 250 g.m-2) which was spread by hand to attain 75% groundcover on a 1:1 slope. After the three months, soil sampling was done to determine the changes in aggregate stability of soil. Results showed that the most efficient treatment with respect to mean weight diameter of soil aggregates in dry and wet sieving (MWDdry and MWDwet), aggregate stability index (AS) and aggregate destruction index (DI) was treatment of B (150 g.m-2 wheat straw mulch and 3 g.m-2 Polyacrylamide tackifier) with 34%, 68% and 47% increment in MWDdry, MWDwet and AS, respectively as well as 37% reduction in DI as compared to the bare soil control.

The objective of this study was to evaluate the effect of a year of cultivation and three agronomic measures (pre-crop, soil tillage, application of fungicides) on the yield of winter wheat grown in the crop rotation without the livestock production. The results from the years 2011-2017, except for the year 2012, from the Žabčice Field Experimental Station (49°01'20''N, 16°37'55''E) were evaluated. The soil texture is clay loam soil and the soil type is fluvisol. In the field trial, winter wheat was grown after two pre-crops (winter wheat, pea). Two soil tillage technologies, namely the conventional tillage - CT (ploughing - at a depth of 24 cm) and the minimum tillage - MT (shallow loosening - at a depth of 15 cm) were used. Two fungicide treatments against leaf and spikelet diseases were used, and they were compared to the non-treated variants. The obtained results showed that the grain yield of winter wheat was statistically influenced not only by a year of cultivation, but also by the pre-crop, the application of fungicides, and mostly by the interaction of these factors with the soil tillage. The importance of pea as a suitable pre-crop for winter wheat was confirmed as the grain yield was higher compared to winter wheat as a pre-crop by an average of 0.49 t/ha. It was also found that the MT is a more appropriate technology than the CT, on average by 0.12 t/ha over the six years. The importance of fungicide treatment was also confirmed, where the grain yield of winter wheat was higher by 0.26 t/ha compared to the non-treated variant. The presented results brought a new knowledge for winter wheat management practice in dry conditions.

Two spring wheat varieties were used to study alleviating effects of exogenous spermine (Spm) and spermidine (Spd) on agronomic traits and photosynthesis under high temperature treatment (HT). Our results showed that HT significantly decreased grain mass per panicle of heat-resistant variety (XC 6) by 25% and heat-sensitive variety (XC 31) by 32%. After HT, i.e., at 13 d after flowering, the decrease in net photosynthetic rate of XC 6 (38%) was lower than that of XC 31 (53%); the reason for this was related to XC 6, which could maintain correspondingly normal chlorophyll content (Chl), stomatal conductance (gs), transpiration rate (E), and intercellular CO2 concentration. Exogenous Spm and Spd could increase relative water content, Chl, gs, E, the maximal quantum yield of PSII photochemistry, effective quantum yield of PSII photochemistry, antenna conversion efficiency, and photochemical quenching coefficient of flag leaves under HT. Our results indicated that the heat resistance of XC 6 is better than that of XC 31 and exogenous Spm and Spd could alleviate the heat injury of photosynthesis of wheat flag leaves.

The effects of feeding rabbits a diet that includes wheat enriched with anthocyanins were examined in this study. In addition to the animal's performance, the basic carcass yield indicators and the basic indicators of the clinical biochemistry were also evaluated. The experiment was carried out using 18 HYLA female rabbits. The trial was performed at the age of 42 to 103 days. The experimental group (n = 9) received a pelleted feed mixture containing 15% PS Karkulka wheat. The control group (n = 9) received a pelleted feed mixture containing the common wheat variety Vanessa with a minimal anthocyanin content. There were no significant differences (P > 0.05) between the control and experimental group in the live weight on the 103rd day. The same trend was found in the average weight gain per trial and in the feed conversion ratio. The average feed consumption was higher (P < 0.05) in the control group compared to the experimental group. There was also a higher (P < 0.05) carcass weight in the control group of the rabbits compared to the experimental group. There were no differences in the percentage carcass yield between the groups. The biochemical indicators and antioxidant activities did not differ between the two groups of rabbits (P > 0.05). Based on these findings, it can be concluded that the use of 15% PS Karkulka wheat in the feed ration for HYLA broiler rabbits was safe and may be fed to broiler rabbits.

Mixolab has been used for rapid assessment of common wheat quality, but data about hulled wheats quality are rare. The aim of this work was to test the potential of Mixolab II in the baking quality evaluation of emmer wheat varieties. The varieties were characterised by low both - gluten content (1.7-11.0%) and Zeleny sedimentation (11.3-12.8 ml), as well as rheological properties showed lower baking quality. Significant differences in protein and starch-amylase part of Mixolab curve indicate the genotype and climatic effect. In average, emmer varieties were characterised by high protein weakening (C2 - 0.29 Nm), speed of protein weakening at the level of α = -0.05 Nm/min, starch gelatinisation (C3 - 1.61 Nm), amylolytic activity (C4 - 1.35 Nm) and starch retrogradation (C5 - 1.98 Nm). Zeleny test positively correlated with difference C1-C2 and slope α. Falling number positively correlated with C3, C4, C5 and slope γ. Farinograph dough stability, gluten content together with Mixolab parameter C2 are the most promising characteristics to predict baking quality of emmer.

A 2-year field experiment was carried out in loessal soil in a semi-humid climate to research winter wheat (Triticum aestivum L.) growth and nitrogen use efficiency. The result showed that subsoiling increased root penetration and promoted deep soil water absorption, which resulted in high resilience to the adverse dry climate. Soil NO3--N residue throughout the profile was decreased but increased in rotary tillage. Grain yield was significantly increased by 21.9% and 11.3% in 2016 and 2017, respectively, mainly due to the significantly larger spikes per hectare and grains per spike. Nitrogen use efficiency was significantly improved by 26.7% in 2016 and 13.8% in 2017. For loessal soil in semi-humid climate, breaking the plough pan was necessary, and it was useful for the increase of grain yield and nitrogen use efficiency.

Whole grain wheat flour (WG) of three different particles sizes (194.9, 609.4, and 830.0 µm) was prepared by milling whole grain. The effect of particle size on the thermo-mechanical properties of flour was investigated using Mixolab equipment and solvent retention capacity (SRC). The results showed that particle size influences the functionality of the gluten network. The SRC test revealed that the water absorption increased from 77.43% to 85.76%, with decrease in particle size. The C2 (protein weakening) values were correlated with the values for water absorption in the SRC and wet gluten test, respectively. The degree of gelatinization of starch (C3) showed that the presence of the fibers in the WG samples limited the availability of water to the starch, and this effect was especially true for flour with smaller particle size. In summary, the Mixolab equipment allowed a better understanding of the functionality of WG with regard to the behavior of protein properties. WG with coarse particles demonstrated a greater impact on the gluten network, indicating a negative effect on the baking quality.

Water saturation deficit (WSD) is a parameter commonly used for detection of plant tolerance to temporary water shortages. However, this parameter does not meet criteria set for screening. On the other hand, measurement of chlorophyll (Chl) a fluorescence is a fast and high-throughput method. This work presents the application of learning systems to set up a model between WSD and Chl a fluorescence parameters allowed for development of a new screening test. Multilayer perceptron (MLP) was trained to predict WSD values on the basis of Chl a fluorescence. The best MLP consisted of three inputs: maximal quantum yield of PSII photochemistry, approximated number of active PSII reaction centres per absorption, and measure of forward electron transport, three hidden nodes and one output (WSD). The MLP precision was 82% with a correlation coefficient of 0.98. Continuous improvement of MLP structure and model adaptation to new data takes place. (1)