Dataset on the effects of plant density and micronutrient fertilization on sunflower growth and photosynthetically active radiation under semi-arid conditions of South Africa

This dataset was generated from a field experiment conducted to evaluate the effects of plant density and micronutrient fertilization on sunflower (Helianthus annuus L.) growth and canopy photosynthetically active radiation (PAR) under semi-arid conditions in the North West Province of South Africa. The experiment was carried out during two consecutive growing seasons (2022/23 and 2023/24) at the North-West University Experimental Farm (Molelwane) and the Department of Agriculture Experimental Farm at Taung. The experiment was arranged as a 5 × 3 factorial in a split-plot design with four replications. The main plot factor consisted of three plant densities of 37,037, 55,556, and 74,074 plants ha⁻¹, established using a constant row spacing of 75 cm and within-row spacings of 30 cm, 20 cm, and 15 cm, respectively. The subplot factor comprised five micronutrient treatments: iron (Fe), zinc (Zn), manganese (Mn), a combined Fe + Zn + Mn treatment, and an untreated control. Nitrogen was supplied as limestone ammonium nitrate (LAN), while phosphorus was applied as single superphosphate. Macronutrient application rates were determined from pre-plant soil analysis and applied by band placement at planting, whereas micronutrients were applied before the flowering stage. Before planting, soil samples were collected from depths of 0–15 cm and 15–30 cm at each site and analysed for pH, nitrate nitrogen, ammonium nitrogen, available phosphorus, exchangeable potassium, iron, zinc, manganese, organic carbon, and particle size distribution. Daily meteorological data, including rainfall, maximum temperature, and minimum temperature, were obtained from the South African Weather Service throughout the study period. The dataset includes measurements of sunflower plant height, stem diameter, number of leaves per plant, leaf area, leaf area index (LAI), and photosynthetically active radiation (PAR) above and below the crop canopy. PAR and LAI measurements were obtained using an AccuPAR LP-80 ceptometer, while other growth parameters were measured using standard agronomic procedures. The dataset also contains soil physicochemical properties, fertilizer application rates, weather records, analysis of variance (ANOVA) outputs, least significant difference (LSD) mean comparisons, and Pearson correlation analysis among the measured variables. These datasets provide a comprehensive resource for understanding the combined influence of plant density, micronutrient nutrition, and environmental conditions on sunflower growth and canopy light interception under semi-arid conditions. The data can be used by researchers, agronomists, crop modellers, extension specialists, and policymakers for comparative studies, meta-analyses, precision agriculture applications, and the development of sustainable sunflower production strategies in water-limited environments. Keywords:Leaf area index, Iron, Zinc, Manganese, Semi-arid.本数据集源自一项田间试验，旨在评估南非西北省半干旱环境下，种植密度与微量营养元素施肥对向日葵（Helianthus annuus L.）生长及冠层光合有效辐射（Photosynthetically Active Radiation, PAR）的影响。试验于2022/23和2023/24两个连续生长季，分别在西北大学试验农场（莫勒尔瓦内，Molelwane）及陶恩农业部门试验农场开展。 本试验采用裂区设计（split-plot design），设置5×3因子布局，共4次重复。主区因子为3种种植密度，分别为37037、55556、74074株·公顷⁻¹，均采用75 cm的固定行距，对应的株距分别为30 cm、20 cm、15 cm。副区因子包含5种微量营养元素处理：铁（Fe）、锌（Zn）、锰（Mn）、Fe+Zn+Mn复合处理，以及未施肥对照。氮肥以硝酸铵钙（Limestone Ammonium Nitrate, LAN）形式施用，磷肥以过磷酸钙（single superphosphate）形式施用。大量元素施用量依据播前土壤分析结果确定，于播种时采用条施方式施加；微量营养元素则于开花期前施用。 播种前，在各试验点位采集0–15 cm和15–30 cm土层的土壤样品，分析其pH值、硝态氮、铵态氮、有效磷、交换性钾、铁、锌、锰、有机碳及粒径分布。本研究周期内的每日气象数据（包括降雨量、最高气温、最低气温）均取自南非气象局。 本数据集涵盖向日葵株高、茎粗、单株叶片数、叶面积、叶面积指数（Leaf Area Index, LAI）以及冠层上下方的光合有效辐射（PAR）等指标。PAR与LAI采用AccuPAR LP-80 冠层分析仪（ceptometer）测定，其余生长参数采用标准农艺程序测定。数据集还包含土壤理化性质、肥料施用量、气象记录、方差分析（Analysis of Variance, ANOVA）结果、最小显著差异（Least Significant Difference, LSD）均值比较，以及各测定变量间的皮尔逊相关分析结果。 本数据集为理解半干旱环境下种植密度、微量营养元素供给与环境条件对向日葵生长及冠层光截获的综合影响提供了全面的研究资源。研究人员、农学家、作物建模者、农技推广专员及政策制定者可利用该数据开展对比研究、元分析、精准农业应用，以及制定缺水环境下可持续向日葵生产策略。 关键词：叶面积指数，铁，锌，锰，半干旱环境。