Wheat (Triticum aestivum L.) production in South Africa's Western Cape province is challenged by high input costs, spatially variable soils and erratic rainfall, indicating potential opportunities for site-specific input management. Uniform input applications often fail to account for the in-field variability, leading to inefficient input use and suboptimal yield returns. Implementing variable-rate application strategies therefore requires a clearer understanding of how soil and management factors interact to influence yield response. This study aimed to determine profit-maximising flat and variable seeding and fertiliser rates under local dryland conditions, and to assess the relative importance of soil physical and morphological properties and management factors in explaining in-field yield variability. Six field-scale on-farm trials were conducted during the 2023 and 2024 seasons as part of the Data-Intensive Farm Management project. Variable-rate management zones within fields were delineated based on observed wheat yield responses to varying seeding and fertiliser input rates. Random Forest models were used to evaluate the contribution of seeding rate, fertiliser rate and soil properties to yield variation across the fields. Profit-maximising rates were determined using direct costs, which included real-time seed and fertiliser costs together with the grain price as received in the respective season. Seeding and fertiliser rates were consistently among the strongest predictors of wheat yield, confirming that yield variability is closely linked to input management decisions. However, soil properties, such as depth for potential root development, type and depth of limiting layers, soil structure, and plant-available water capacity, also exerted significant, site-specific influences. These interactions were non-linear and differed across fields, demonstrating that optimal input management depends strongly on local soil constraints. Overall, the integration of data-intensive experimentation with machine learning provided valuable insights into how management practices interact with soil physical variability to shape yield outcomes. The findings underscore the importance of coupling precision input management with improved understanding and remediation of subsurface soil constraints to enhance productivity and resource-use efficiency in the local dryland wheat systems.
In the Mediterranean climate of the Western Cape, wheat (Triticum aestivum) is the main rainfed grain crop, rotated with pastures, canola (Brassica napus) and barley (Hordeum vulgare). Nitrogen (N) fertiliser is a major input cost, and its selection is critical due to the varying prices and efficiencies. A field trial (2016-2020) evaluated the effects of different top-dressed N sources-ammonium sulphate (AMS), limestone ammonium nitrate (LAN), LAN + sulphur (S), urea, and urea + urease inhibitor-on biomass, grain yield and quality in a Conservation Agriculture system. In South Africa, wheat grain is graded based on protein content, influencing the market price. The biomass, harvest index, grain yield, hectoliter mass and protein content varied significantly by year, but not by N source. Partial profit differences among N sources were not significant in 2017 and 2020. However, in 2016, LAN + S yielded lower profits than urea + inhibitor, while in 2018, both LAN + S and urea + inhibitor outperformed LAN. In 2019, AMS had higher profits than urea + inhibitor. Overall, crop rotation had a greater influence on yield and quality than the choice of N fertiliser.
There is an ongoing debate about the most appropriate approach for quantifying changes in soil organic carbon stocks (SOCS). The aim of the study was to evaluate the performance of the Rothamsted carbon (RothC) modelling approach against the re-measured SOCS (actual) values at field scale in South Africa. The baseline assessment (2022) for two fields in South Africa was established beforehand. Afterwards, 50 samples from three depth increments, 0-5, 5-15 and 15-30 cm were collected, and the SOCS calculated (2024) for two study sites (Ottosdal and Vrede) using the re-measure approach and the modelling approach using the RothC model. The sampling cost was also estimated against the value of sequestered SOCS (2022-2024) and compared between the two approaches. The main finding from the study indicated that more samples being utilised during the modelling approach, using the RothC model, leads to the modelled SOCS values being closer to the actual re-measured values and ultimately more reliable SOCS measurements at field scale in South Africa. The spatial variation of soil organic carbon (SOC) content was the main factor influencing the total SOCS, sequestered SOCS and carbon credit values. The results indicated that the modelling approach using the RothC model slightly underestimated the total SOCS and sequestered SOCS compared to the actual re-measured values for both study sites. The industry-represented 'One-observation' did not have a consistent trend, which had significant financial implications using both approaches. Overall, utilising more samples either in the re-measure or modelling approach would provide more reliable carbon credit values. The study also found that the spatial variation of the SOC content must be taken into account at the onset of measuring the SOC content in the baseline year (first year), independent of whether the SOCS would be modelled or re-measured. The carbon sequestration industry must take the model limitations (such as field scale dynamics and sensitivity to short-term changes) into account and find ways to address these limitations of the RothC model at field scale.
In a greenhouse experiment conducted in Mohammedia, drought stress responses were evaluated under two treatments (100% and 50% of field capacity; FC) in six Moroccan chickpea varieties: Arifi, Bouchra, Farihane, Moubarak, Rizki, and Zahour. The susceptibility index (SI) clearly differentiated the varieties, with less negative SI values indicating greater drought tolerance. Rizki (-33%) and Moubarak (-59%) represented the two extremes. Root/whole- plant ratio (R/WP) values increased in Rizki, from 1.00 to 1.36, but declined in Moubarak, from 1.19 to 1.06, mirroring their SI differences. Leaf water content followed the same trend. Across ions, varieties with less negative SI tended to maintain leaf Mg2+ and Fe2+ at 50% FC, whereas more susceptible lines showed weaker maintenance, an observational pattern aligned with the panels. Using the 100%/50% FC bench test together with SI, R/WP, and the observed leaf Mg2+/Fe2+ pattern offers a straightforward and practical way to screen chickpea varieties for drought tolerance in Moroccan breeding programmes.
Crop rotation serves as a fundamental pillar within conservation agriculture (CA) farming systems, enabling the integration of more diverse crops and livestock. With increasing weather variability, new methods are needed to assess the long-term effects of diversification on the agronomic performance of wheat-canola rotations. Therefore, a 17-season Western Cape rotation platform (Mediterranean-type rainfall; eight systems (A-H), livestock integrated leys), and evaluates small grain performance as means, year-to-year stability (CV%) and grain quality. The long-term data were compared using the Functional Diversification Index (FDI), which summarises sequence richness/evenness, cereal-oilseed-legume contrast, cover/ley phases, planter/tillage choice and livestock intensity. This first long-term Western Cape study using an FDI index validated over 17 seasons shows that the most diverse system, wheat-saltbush-medic/clover mix (System H), had the highest relative mean yield stability (similar to 16.90%), while wheat monoculture under reduced tillage had the lowest (similar to 41.16%). The highest wheat protein content is strongly associated with livestock integrated systems (E-H). These findings highlight the interrelationship between diversification practices and agronomic performance in CA systems in the Swartland region. Under Mediterranean-type rainfall, when mean yields are similar, farmers should prioritise rotations with the lowest yield CV% to reduce year-to-year risk while maintaining grain quality.
Knowledge of trait genetic control in sugarcane breeding is limited but is required to develop breeding strategies that optimise trait breeding. The objective of this study was to determine additive and non-additive genetic variance for sucrose content, and to evaluate genetic control and its implications on breeding strategy. Data for Brix% (a proxy for sucrose content) were collected from unselected progeny plots nested within replicated family plots in six irrigated and six rainfed trials and analysed using linear mixed models. Female variance was significant (p < 0.05) in eight trials, while male variance was significant in three trials, suggesting dominant maternal effects. Female x male interaction variance was significant (p < 0.05) in six trials from older breeding programs, suggesting presence of non-additive genetic effects. The proportion of parents (6.2%) producing significant additive and breeding values was higher than crosses (2.4%) producing significant non-additive values. Female and male variances were larger than female x male interaction variance in nine out of twelve trials, further suggesting predominance of additive genetic control. Young breeding programs produced higher additive variance while older programs produced higher non-additive variance. Selecting parents producing high breeding values and optimising cross-combinations will develop progenies that produce higher sucrose content.
Crop rotation is a key component of conservation agriculture, known to enhance yields and break the cycles of pests and diseases. In the Western Cape, South Africa, canola has become an increasingly important cash crop, with producers considering shorter rotation periods to boost profitability. However, concerns remain regarding yield stability, economic returns and disease pressure from particularly Sclerotinia stem rot. The study utilised a regionally significant eleven-year dataset from a long-term field trial (2013-2023) near Riversdale, Western Cape, to assess these concerns. Shortened rotations (one to two years between canola plantings) were compared to conventional longer rotations between canola crops. Results show that shortened rotations delivered competitive yields and significantly higher gross margins (up to 20%), despite higher input costs. Stem rot incidence was highly variable across years (ranging between 0% and 40%) and was primarily driven by rainfall during flowering, with no consistent correlation with rotation length. Overall, the study indicates that with appropriate management, shortened canola rotations are economically viable for producers, offering a profitable alternative amid declining cereal crop margins. Although not measured in this study, preventing future herbicide resistance will require integrated weed and disease management to support long-term sustainability.
Soil-bedrock interaction on hillslopes is not well-studied, though it's affected by many physical and chemical factors. The aim of the present mathematical modelling study is to construct a model for soil formation utilising ordinary differential equations, all while reducing the number of required parameters. Parameters known from previous studies include, but not limited to, precipitation, temperature, soil properties, slope angle, soil depth, bedrock properties, topography and earthquakes. Due to correlations among the parameters, it is possible to consider all of them using three independent parameters: growth rate of soil (s1(t)), increasing rate of soil due to interaction (s2(t)) and decay rate of soil due to erosion (s3(t)). One population increases by destroying another, which is most common in predator-prey dynamics. By comparing the bedrock to prey and the soil to predators, we can create a mathematical model that accurately captures this complex interaction. Previous data sets suggest periodic, linear, exponentially decreasing or constant for different domains of study. The predator-prey model has been solved numerically using fifth-order Runge-Kutta in MATLAB. The actual and calculated soil volume differs by 0.00121 m3, while the biomass content difference is 2.28%, resulting in about 97% accuracy.
Efficient phosphorus (P) extraction methods are vital for optimising sugarcane production, yet no single chemical extractant currently suits the diverse soil conditions across South Africa's sugarcane regions. This study explored the potential of anion-exchange-resin phosphorus (AER-P) as a possible alternative to conventional P extractants. The novelty of this study lies in evaluating AER-P in the local context, offering a potential unified method for P assessment across varying soils. The field experiment involved varying levels of P and nitrogen (N) applied in a randomised design with four replications. The results revealed that soil AER-P increased significantly (p < 0.05) with increase in P fertiliser from 8.52 to 49.91 mg l(-)(1) and positively correlated with P concentration in sugarcane leaves. Leaf P and yield properties tracked AER-P at moderate strength (R-2 approximate to 0.50-0.52) and plateaued at similar to 40 mg l(-)(1) of AER-P associated with the rate of 100 kg P ha(-)(1). Elevated N levels led to a notable decrease in soil pH and a modest decline in base cations and cation exchange capacity (CEC). These findings highlight the potential of AER-P as a reliable indicator of P availability in sugarcane soils. However, a broader validation across multiple seasons and climatic zones is necessary before widescale adoption.
Pre-harvest sprouting (PHS) in wheat (Triticum aestivum L.) is an increasing concern, as climate variability alters rainfall patterns and air temperatures during harvest, intensifying risk in many cereal-producing regions. The untimely germination of the grain, PHS, is caused by germination of the grain in the spike before harvesting and leads to alpha-amylase synthesis, reduced falling number, and lower grain yield and quality. Despite widespread use, the relationships between visual assessment, falling number, and alpha-amylase assays remain inconsistent. This study, conducted over two seasons (2021-2022) at two sites in the Eastern Cape, South Africa, evaluated commercially available wheat cultivars using the three PHS assessment methods listed above. Visual scores ranged from 1 (no sprouting) to 8 (fully sprouted), while falling number and alpha-amylase were analysed using standardised protocols. Correlations (p < 0.05) were observed between falling number and alpha-amylase but not between visual assessment and biochemical assays. The results highlight the fact that the three methods apply to different stages of germination. Visual scoring provides additional information to biochemical tests and is valuable in a multi-method screening protocol. This approach would enhance the accuracy and consistency of PHS evaluation in local breeding programmes and quality control under increasingly variable climates.
Thinopyrum distichum (Thunb.) & Aacute;. L & ouml;ve is a salt-tolerant, wheat wild relative native to the Western Cape and Eastern Cape coastal regions of South Africa; however, the mechanisms governing this species' halophytic nature remain underexplored. RNA was extracted from root and shoot tissues of Th. distichum under acute salt stress (350 mmol l-(1) NaCl) for qPCR. Expression changes in osmotic adjustment (NCED1, NIP), reactive oxygen species (ROS) homeostasis (SRO1, PRX), and ion homeostasis via the salt overly sensitive (SOS) pathway (HKT7, NHX2) in shoots and roots were analysed. HKT7 was downregulated in both tissue types, with a statistically significant downregulation in the shoots (average log2(FC) = -2.160, p = 0.008), suggesting Th. distichum may maintain ion homeostasis by accumulating salt via the SOS pathway. No statistically significant variation in NCED1, NIP, SRO1, PRX or NHX2 gene expression was seen. This study provides insight into the biological mechanisms responsible for abiotic stress tolerance and underscores the potential of transferring Th. distichum genes for enhancing wheat salt tolerance in South Africa.
Farmers in southern Ethiopia integrate versatile trees with annual crops; yet, scientific data on their impacts on soil properties and crop yields remain limited. This research evaluated the impact of Croton macrostachyus (Hochst. Ex Delile) and Erythrina brucei (Schweinf) canopies on soil properties and wheat yield across different radial distances from the tree trunks, in Gamo, southern Ethiopia. The randomized complete block design (RCBD) experiment was applied, incorporating two tree species replicated four times for each and four radial distance treatments. Soil and wheat data were analysed using two-way ANOVA. The findings demonstrated significant enhancements in soil properties and wheat yields under both tree canopies, with peak yields observed at two-thirds of the crown radius. Since this study was conducted over a single season and focused on just one crop, future research should incorporate multi-seasonal and regional data, as well as variations in soil depth.
Long-term applications of pig slurry (PS) can lead to phosphorus (P) accumulation in soil, but its distribution across soil profiles remains poorly studied, particularly after 50 years of PS application on pasture soils, compared to undisturbed and cropped Luvisols, and across different durations on Ferralsols under maize-soybean rotations in KwaZulu-Natal, South Africa. Estimated annual P additions through PS were 147 kg P ha-1 in Luvisol and 58.8 kg P ha-1 in Ferralsol, plus 30 kg ha-1 from mineral fertiliser. Soil samples from multiple depths were analysed for total P, available P, and other P fractions. Total P increased to 2 824 and 3 415 mg kg-1 in Luvisol and Ferralsol, respectively. Available P reached 101 (Luvisol) and 112 mg kg-1 (Ferralsol) in the top 400 mm of soil. Organic P also increased, reaching 2 597 mg kg-1 (Ferralsol) and 1 891 mg kg-1 (Luvisol). In both soils, Fe-P (355 and 491 mg kg-1) and Al-P (255 and 239 mg kg-1) increased after over 20 years of PS application. In Luvisol, Al-P accumulation (255 mg kg-1) was confined to the top 100 mm, while in Ferralsol it extended to 400 mm. This indicates a low risk of leaching but a high risk of surface water pollution through runoff and erosion. The study underscores the importance of monitoring the effects of PS application to mitigation environmental risks while maintaining soil fertility.
The implementation of precision agriculture practices can enhance agricultural productivity, sustainability, and on-farm profitability. Nonetheless, adoption rates vary widely across regions and farming operations, particularly in South Africa's diverse agricultural landscape. This study builds on prior regional analyses by providing the first national-scale assessment, offering new insights into adoption patterns and barriers among diverse field crop contexts. A national survey was conducted using industry networks, gathering responses from producers working with different crop types, farm sizes, and across multiple provinces. Our findings suggest that adoption of precision agriculture is more widespread than previously reported, especially for practices such as yield mapping, soil sampling, and variable rate applications. Contrary to common assumptions, producer age and farm size did not emerge as factors influencing adoption decisions. However, significant barriers remain, including high initial investment costs and limited awareness of technology capabilities. Regional differences were also observed, with lower adoption in winter cropping regions. These insights highlight the need for targeted strategies and improved communication to help producers realise the full potential of precision agriculture, particularly for nutrient management and sustainable intensification. By understanding current adoption patterns, policymakers, technology developers, and agricultural services can be guided to better promote the wider and more effective use of precision agriculture technologies in South African field crop systems.
