Sustainable Soil Management and Crop Production Research

Soil provides crop plants with the essential nutrients, water, and root support they require to grow and thrive. There are a number of factors that affect soil quality, including climatic conditions, time, living organisms, and, especially, the human management of soil [1]. The soil condition determines the effectiveness of any crop. The use of mineral fertilizers and plant protection products has steadily increased over the last century, adversely impacting soil conditions and the environment [2,3]. The inefficient use of nutrients in fertilizers has resulted in the migration of harmful compounds. Intensive cultivation and the use of mineral fertilizers have adversely affected biodiversity, resulting in significantly reduced physical and chemical properties in the soil [2]. Thus, the problem of environmental pollution has become global.

In this regard, agriculture has a significant impact on natural resources, which could adversely affect environmental protection and result in the degradation of agricultural lands. In response to this situation, a heated debate has emerged over the need for better fertilizer management and more sustainable soil nutrient use, highlighting the importance of integrating methods and practices designed to achieve adequate plant nutrition and productivity. New agricultural practices, fertilization methods, amendments, and plant nutrition sources, along with the use of bacteria and fungi to enhance nutrient utilization by crops, all provide interesting and sustainable solutions for maintaining soil life, improving fertility, and feeding plants in order to promote sustainable agricultural production. In addition, the use of new and/or existing sources of fertilizers and soil improvers, either directly (direct input into the soil) or indirectly (physicochemical transformation), is beneficial to minimize contamination and environmental impacts. For this reason, understanding nutrient reactions and processes in soils (soil fertility), as well as managing inorganic and organic nutrient input efficiently (nutrient management), is essential to maximizing nutrient supply to crops and minimizing environmental risk.

This Special Issue, entitled “Sustainable Soil Management and Crop Production Research”, is a collection of six articles (five research articles and one review article) focusing on recent scientific progress and innovation in agriculture regarding the evaluation of the spatial–temporal variability of nutrients for precise prescription, the assessment of crop responses to nutrient application, the development of integrated nutrient management (INM) strategies for sustaining soil health and crop productivity and quality, the improvement in nutrient use efficiency (NUE), the establishment of critical limits for nutrients under different soil–crop conditions for revising nutrients recommendations, and the development of best management practices (BMPs) for nutrients under various soil–crop conditions.

In the crop production cycle, tillage constitutes one of the most energy-intensive and cost-prohibitive operations [4,5]. Through the use of tillage tools, energy is directed into the soil, causing certain effects including cutting, breaking, inversion, and movement of the soil. This process converts soil from a stiff, bulky, and compacted condition to a desirable pulverized one. In sustainable crop farming, tillage is an important operation for achieving the Sustainable Development Goals, such as Zero Hunger (SDG-2), Responsible Consumption and Production (SDG-12), Life of Land (SDG-15), and Climate Action (SDG-13) [6]. An investigation was conducted by Singh et al. (Contribution 1) to determine the performance of the spading machine as an example of sustainable tillage implement at various depths of tillage. In this study, the spading machine was assessed based on two distinct variables including soil type (sandy loam, sandy clay loam and sandy soil) and depth of cut (100, 150 and 200 mm). As tillage depth increased, the dependent parameters, including soil bulk density, mean clod size, soil strength, torque requirement, fuel consumption, and operating cost increased as well, except for the operating cost, which was not significantly affected. Other primary tillage tools (MB plough, disc plough, and rotary tillage tool) produced higher bulk densities and fuel consumption compared with the spading machine, while mean clod size and cost of operation were lower except for the rotary tillage tool. Consequently, the authors noted that the spading machine might be beneficial for long-term agricultural purposes as a sustainable tillage implement.

As a pivotal agricultural resource in southern China, red soil accounts for approximately 22.7% of the country’s land area [7]. In spite of this, inappropriate tillage methods have degraded topsoil and lowered soil quality. According to Yan et al. (Contribution 2), four tillage practices were examined on red-soil sloping farmland, including cross-slope ridge tillage (RT), down-slope ridge tillage (DT), plastic mulching (PM), and conventional tillage (CT). This study also utilized the Soil Management Assessment Framework (SMAF) to assess the impact of these tillage practices on soil quality. A comparison of soil physicochemical properties under the above-mentioned tillage methods demonstrated that PM was more porous, capillary, and saturated with respect to total porosity and capillary porosity; however, RT was more abundant with soil macro-aggregates, mean weight diameter, geometric mean diameter, and soil water-stable aggregate stability. Furthermore, both PM and RT practices produce higher levels of total nitrogen, organic matter, available phosphorus, and available potassium, with RT demonstrating the highest soil quality compared to PM. There has been a positive impact of crop growth on soil macroaggregate content and stability, indicating an improvement in soil structure and quality over time. This study concluded that, in red-soil sloping farmland, RT should take precedence over PM and CT, with DT avoided if feasible.

Through the application of leguminous trees as alley cropping, soil fertility is protected and increased, water is improved by intercepting pesticides, the local climate is modified, biodiversity is improved, and productivity is improved. Hammad et al. (Contribution 3) conducted a two-year experiment to investigate how alley cropping affected the growth and productivity characteristics of fennel (Foeniculum vulgare Mill.). The study revealed that fennel growth and yield can be increased by sesbania-fennel alley cropping with N fertilizer supplementation and endophytic fungi such as Chaetomium globosum. In the present investigation, legume trees were sown at an optimal spacing (4 or 6 m) with a height of 1.25 m to boost the fennel production. Furthermore, incorporation of Sesbania leaves as green manure resulted in greater fertility of the soil as well as a greater availability of nutrients, which in turn enhanced fennel’s growth and productivity.

Sweet pepper (Capsicum annuum L.) is the third-largest cash crop in the nightshade family after tomatoes and potatoes [8]. In addition, it is a concern worldwide that climate change is having a detrimental impact on crop productivity. Climate change is having an adverse effect on the growth, yield, and quality of vulnerable crops, including sweet peppers and other chili pepper types [9]. In an evaluation of the most optimal planting date and most productive cultivar of sweet pepper under the impacts of climate change, Zakir et al. (Contribution 4) set up an experiment in Multan, Pakistan. Study findings revealed that the ‘Winner’ cultivar provided the highest yield, postharvest life, and overall crop performance when planted on 25 January, validating the benefit of planting early. In general, the present research recommended to transplant a 40-day-old sweet pepper nursery on 25 January in order to obtain the best possible growth performance, production, and fruit quality under the environmental conditions of the studied area.

Cassava (Manihot esculenta Crantz) is a staple food that is typically cultivated with low management inputs, resulting in soil depletion and low yields. The utilization of humic substances, the main constituents of natural organic matter which found in both terrestrial and aquatic environments, is a sustainable way to boost cassava crop performance and yield, particularly in semi-arid regions like the Brazilian Northeast [10,11]. For this reason, Santos et al. (Contribution 5) investigated the effects of foliar application of a biostimulant derived from humic compounds (BHS) on cassava morphology, physiology, production, as well as mineral nutrient content in Bananeiras, Brazil. The foliar application of BHS reduced photosynthetic activity and nitrogen uptake while having no effect on cassava plant growth or yield. A foliar application of 3 kg ha⁻¹ BHS is not suggested for cassava based on the analyzed application mode, frequency, climate, and soil parameters. The authors of this research also noted that more research is needed to compare alternative BHS doses and application techniques aimed to enhancing cassava crop production.

Over the last century, organic farming, which has its roots in traditional agricultural methods, has undergone substantial change [12]. From a grassroots movement against agricultural industrialization to a multinational industry, organic farming has played a significant role in tackling modern issues including food safety, sustainability, and environmental health [13]. A thorough analysis of the beginnings and development of organic farming was given by Panday et al. (Contribution 6), with an emphasis on the advantages and drawbacks of various types of organic fertilizers. According to this review article, nutrient variability and the slow-release nature of organic fertilizer usually fail to meet crop demands, resulting in a considerable drop in crop output. Some organic fertilizers, such as manure and biosolids, can enhance yields, but they also pose environmental and health hazards. A synopsis of the current organic fertilizer certification procedure, complete with technical specifications, is also included in this article. It demonstrates that the comprehensive approach of organic farming goes beyond production, including methods like reducing food waste and creating self-sufficient farming communities. Additionally, this study highlighted how specific organic fertilizer formulation can benefit from future technological improvements, notably in precision agriculture and bio-physicochemical models.

In summarizing, these manuscripts provide valuable insights into the methods and practices that contribute to interesting and sustainable solutions for maintaining soil life, improving fertility, and feeding plants in order to promote sustainable agricultural production; however, all the authors of the present Special Issue agree that much more intensive field work and field research should be carried out, as well as more experimental work in order to promote sustainable soil management and crop production.