The main objective of this study was to analyze variable rate seeding (VRS) methods and critically evaluate their suitability and effectiveness for the challenges under field conditions. A search was performed using scientific databases and portals by identifying for analysis and evaluation 92 VRS methodologies, their impact and economic benefits depending on the main parameters of the soil and environment. The results of the review identified that VRS could adapt the appropriate seeding rate for each field zone, which was based on site-specific data layers of soil texture, ECa, pH and yield maps. Then, remotely detected images or other data which identify yield-limiting factors were identified. The site-specific sowing method (with a variable sowing rate for each field area) allows the optimization of crop density to obtain the best agronomic and economic results. Various proximal and remote sensor systems, contact and contactless equipment, mapping and VRS modeling technologies are currently used to determine soil and crop variability. VRS depends on the field characteristics’ sowing equipment capabilities, the planned harvest, soil productivity and machine technology interactions with the environment. When forecasting the effective payback of a VRS over the desired period, the farm size should on average be at least 150 ha. In future studies, to achieve the best solutions and optimal methods, it is important to test, evaluate and put into practice the latest methodologies on farms, to perform complex assessments of changes in sensor, soil, plant and environmental parameters.

Reducing the overuse of mineral fertilizers in crop production is a key factor related to healthier soil, healthier food, and more economical, efficient, and cleaner agricultural production. The aim of this study was to investigate and to compare the effects of fixed and variable rate fertilization with fertilizer consumption, energy consumption, and environmental impact. A 4-year experimental field study using crop rotation of four plants (spring barley, winter oilseed rape, winter wheat, and faba bean) was performed. Fertilization with phosphorus and potassium at a variable rate were performed and applied based on the soil properties analyzed before the start of the research and completion of the fertilization maps. Nitrogen fertilization was performed by additional fertilization using a proximal N-sensor, which gives the accurate nitrogen uptake in plants in real-time. This was followed by a comparative evaluation analysis of variables and conventional fixed-rate fertilization methods to assess fertilizer consumption, energy consumption, environmental impact, and economic efficiency. The results of the study showed that an application of a variable fertilization rate can reduce the total amount of nitrogen, phosphorus, and potassium fertilizers by 24.9%, energy consumption by 3463.1 kg ha⁻¹, and emissions of greenhouse gases (GHG) by 341.5 kg CO_2eq ha⁻¹ compared to fixed fertilization rate. The method of fertilization with a variable application rate reduced the costs of fertilization, and at the same time, the costs of the total plant production by €168.0 ha⁻¹, on average.

Sowing or seedbed depth is an important agro-technological parameter that varies with specific on-field soil and microclimatic conditions and depends on crop biology. There is a lack of detailed information regarding how seedbed depth relates to other seedbed parameters and affects the development of agricultural crops. Several seeder constructions and methods for seeding condition detection and depth adjustment have been investigated in high-precision, digitally backgrounded, in-site sowing systems; however, there is still a gap in knowledge due to the limited use of these technologies in conditions of high soil and micro-climatic variability. Therefore, the aim of this study was to highlight the impact of sowing depth on crop seedbed parameters, mainly established by the Kritz method, to ascertain the correlation between sowing depth, germination, crop development and productivity, and to overview the methods and equipment used for detection, adjustment and control of sowing depth in precision site-specific sowing systems. Our results showed that, in most cases, when sowing depth extended beyond the optimum, the moisture content in the seedbed decreased significantly. Sowing depth also correlated with the roughness of the seedbed (surface and bottom) and seedbed aggregate size distribution, but the direction of the relation depended on crop type and maximum sowing depths. Sowing depth correlated with crop germination, development and productivity parameters; however, the direction of exposure and intensity also varied with respect to crops, weather conditions, tillage and sowing equipment. Sowing depth uniformity is greatly influenced by the regulation of clamping force, the spatial variability of soil in fields and sowing operation speed.

Wheat is among the world’s most important agricultural crops, with winter wheat accounting for approximately 25.5% of the total agricultural crop in Lithuania. The unchangeable goal of crop production is to achieve good and economically beneficial crop yield, but such efforts are often based on conventional agrotechnological solutions, and excessive fertilization, which is uneconomical and negatively affects the soil, the environment, and human health. In order to produce a rich and high-quality cereal crop, scientists and farmers are increasingly focusing on managing the sowing and fertilization processes. Precision technologies based on spectrometric methods of soil and plant characterization can be used to influence the optimization of sowing and fertilizer application rates without compromising crop yield and quality. The aim of this study was to investigate the effect of site-specific seeding and variable-rate precision fertilization technologies on the growth, yield, and quality indicators of winter wheat. Experimental studies were carried out on a 22.4 ha field in two treatments: first (control)—SSS (site-specific seeding) + URF (uniform-rate fertilization); second—SSS + VRF (variable-rate precision fertilization) and 4 repetitions. Before the start of this study, the variability of the soil apparent electrical conductivity (ECa) was determined and the field was divided into five soil fertility zones (FZ-1, FZ-2, FZ-3, FZ-4, and FZ-5). Digital maps of potassium and phosphorus precision fertilization were created based on the soil samples. Optical nitrogen sensors were used for variable-rate supplementary nitrogen fertilization. The variable-rate precision fertilization method in individual soil fertility zones showed a higher (up to 6.74%) tillering coefficient, (up to 14.55%) grain yield, number of ears per square meter (up to 27.6%), grain number in the ear (up to 6.2%), and grain protein content (up to 12.56%), and a lower (up to 8.61%) 1000-grain weight on average than the conventional flat-rate fertilization. In addition, the use of the SSS + VRF method saved approximately 14 kg N ha⁻¹ of fertilizer compared to the conventional SSS + URF method.

Sustainable and responsible agricultural production is one of the keys to keeping people, animals, soil, and the environment healthy. Precision seeding technologies for winter wheat, exploiting the variability of soil properties and adapting the technological processes of variable rate seeding and variable seeding depths, are essential not only to improving plant productivity and economic benefits but also to cleaner agricultural production. This work aimed to carry out a life cycle assessment (LCA) of winter wheat production and determine the environmental impact of different precision seeding technologies in terms of individual impact categories compared to conventional seeding technology. Experimental studies were carried out between 2020 and 2022 using conventional uniform seeding rate (URS) and several precision seeding technologies: in the first year—VRS for variable seeding rate and VRS + VRF for variable seeding rate and fertilizer rate, and in the second year—VRS and VRSD for variable seeding rate and variable depth, and VRSD + VRF for variable seeding rate, variable depth, and variable fertilizer rate. The results obtained for winter wheat grain yield showed that the effect of precision seeding technology on the increase of grain yield was not significant compared to the URS. A greater influence on grain yield was found in individual soil management zones, especially in the zone with the worst soil fertility. The LCA did not show any significant differences between precision seeding technology and conventional technology in any of the environmental impact categories. The GWP values (0.200–0.236 kg CO_2eq kg⁻¹) were most dependent on grain yield, as precision seeding technology had small changes in the amount of inputs (seeds and fertilizers), while all other technological operations were the same as under the URS technology. The amounts of phosphorus and potassium fertilizers decreased by 1.4 and 7.9%, respectively, and the amounts of winter wheat seeds and nitrogen fertilizers increased by 4.1 and 5.4%, respectively, compared to the URS.