Agriculture is constantly evolving and technology is present in all processes. It is no different when it comes to fertilization. The recommendation for only one crop has been improved to a concept of using the agricultural production process as a system, optimizing the use of resources and increasing the efficiency of the cultivation process, in addition to reflecting on sustainability.
Fertilization systems are based on the biological cycling of nutrients between the phases of a crop rotation system, in addition to seeking maximum efficiency in the use of nutrients and reducing inputs, without losing soil fertility in the long term (ASSMANN et al., 2014). According to Zortéa (2021), this approach generally contrasts with the recommendations for fertilizing agricultural areas carried out in the traditional model, with specific fertilization of the crop to be planted, which is most often grains. In the traditional fertilization model, only the isolated effect of a given nutrient is evaluated, rarely analyzing the residual effect of these fertilizations, as well as the changes that they can cause in the soil-plant-animal system (ZORTÉA, 2021). The fertilization of systems (Figure 1) considers all crops involved in the rotation (agricultural crops, green manures and pastures) in the dynamics of nutrient recycling between crops, which can occur directly via inorganic forms or indirectly via organic forms resulting from the mineralization process (ASSMANN & SOARES, 2016).
Figure 1. Fertilization management systems. Source: Freitas, 2021.
The main agents that act in nutrient cycling and are the basis for understanding fertilization systems are soil microorganisms, which play a fundamental role in soil maintenance. Among its various functions, soil microbiota is responsible for nutrient cycling in the system, and its biomass is also a potential reservoir of nutrients for plants (ZORTÉA, 2021). Therefore, one of the ways to achieve agricultural sustainability is to employ production systems that maximize the activities of soil microbiota (KLEINA, 2018).
The use of system fertilization can be carried out in different systems, thus, two examples that are widely spread in Brazil can be cited: the cultivation of sequential agricultural crops with the use of direct planting, alternating agricultural crops in harvest, off-season; summer crop and winter crop, among other ways of producing in an agricultural year; and integrated agricultural production systems that tend to be efficient in cycling due to the presence of the animal component in grazing and that can reduce, in part, the need for fertilization of the subsequent grain crop (ASSMANN et al., 2018).
Fertilization of production systems involves fertilizing more intensively the most responsive crops and using residual fertilization for less responsive crops. Thus, responsive crops, such as cotton, corn, beans and tomatoes, can receive higher doses of nutrients, above their nutritional requirements, and less responsive crops, such as soybeans, are cultivated only with a starter fertilization, or “starter”, and with the residual fertilization of the previous crop (ALTMANN, 2012).
To implement this technology, it is necessary to take into account the pre-existing levels of nutrients, determined through soil analysis, the fertilization and export levels of the previous crop and the demand of the next crop, in addition to possible losses, especially of leachable or volatile nutrients. In sandy soils with low CEC, nutrients, especially nitrogen and potassium, should preferably be applied targeting the specific crop, and not the production system (ALTMANN, 2012).
Since the soybean-corn-soybean succession is the most widely adopted grain production system in no-till farming, in this system, the soybean crop is planted in the first harvest and the corn in the second harvest. Because it is highly responsive to fertilization, the corn crop can receive doses above its nutritional requirements. Soybeans are planted with a starter fertilization and benefit from the residual fertilization and organic matter left by the corn. In addition to optimizing soil conditions, the soybean-corn-soybean succession in a no-till farming system also has operational advantages, as it optimizes labor and machinery. Although the soybean-corn-soybean succession is quite consolidated, it is essential to diversify production. This can be done through crop rotation with species that have commercial and soil recovery purposes (BARCELLOS, 2021).
It is necessary to build a production system with a balance between grass and non-grass crops. Grasses are important for straw formation, but due to the high C/N ratio of the straw, they require nitrogen for their decomposition, which requires the cultivation of legumes as commercial crops or soil cover. Likewise, different types of root systems capable of exploring different soil depths are necessary to improve nutrient cycling, avoiding losses due to leaching and contamination of the water table (ALTMANN, 2012).
Fertilization management in integrated agricultural production systems (SIPA) recommends fertilizing pastures in winter to target animal production and subsequent crops through nutrient cycling, allowing for the anticipation of grain crop fertilization, especially N, minimizing losses that tend to occur in summer (ASSMANN et al., 2018; BORTOLLI, 2016; MACCARI, 2016; SOARES et al., 2015), which, according to Sartor et al. (2014), minimizes production costs and environmental impacts. Anghinoni et al. (2013) highlight that moderate grazing promotes greater soil fertility due to nutrient cycling through the contribution of plant residues. However, in systems with higher grazing intensity, there is less residue, which can compromise the system and increase dependence on mineral fertilization.
The traditional form of fertilizer recommendation considers the needs and efficiency of fertilizer use only for the crop being planted. Thus, the residual effect of these fertilizations, as well as the changes that they can cause in the soil-plant-animal system, are rarely evaluated as a possible reason for reducing the application of inputs (ASSMANN et al., 2017). This attitude is based on the interpretation of traditional chemical concepts of soil fertility and plant nutrition, which were conceived mostly under conventional planting system conditions and in temperate climates, where the possibility of more than one crop per agricultural year is rare due to unfavorable climate conditions for this (ASSMANN et al., 2017).
Only in a few situations has the anticipation of the application of macronutrients been observed, for example, on a green manure crop or pastures, and this decision-making is guided more by logistical factors, such as planting speed, than by scientific technical factors. In addition, another concern commonly mentioned regarding the need to apply the three macronutrients is the export of nutrients via grains. In fact, the export of nutrients occurs in large quantities via harvest, which could lead to the depletion of soil fertility. However, there are other components of the system that “store” nutrients and that are commonly disregarded. Therefore, nutrients are also found in the soil, in the remains of straw that remain on the soil after harvest, temporarily immobilized by the microbiological community, and in animal waste, in the case of grazing or that received organic fertilization (ASSMANN et al., 2017).
For Assmann & Soares (2016), the greater efficiency of nutrient cycling and the consequent better use of nutrients in tropical and subtropical cropping systems in Brazil can be attributed to the following factors: no-till system, presence of plants vegetating on the soil throughout the year, soil depth and presence of anion exchange capacity (AEC), forage plants with aggressive root systems, reduced nutrient export and increased soil biological activity.
According to Assmann et al. (2017), within the philosophy of fertilization systems, a new concept that should be incorporated is that soil cover, in addition to being permanent, should be composed of living plants for as long as possible, photosynthesizing and incorporating carbon into the soil. Increases in soil carbon content (carbon sequestration) in addition to contributing to the reduction of greenhouse gases (CO2), make the soil less susceptible to compaction, increasing the infiltration and water retention capacity, thus reducing erosion and surface runoff processes.
Fertilization system recommendation
The recommendation for fertilization of systems constitutes a much more dynamic recommendation and is supported by the interpretation of the production system as a whole and does not only take into account the interpretation of fertilization and liming recommendation tables. (ASSMANN et al., 2017).
FERTILIZATION SYSTEMS – POTASSIUM
Because it is an element that is almost entirely cycled in mineral form, much of the potassium element is not part of the structure of organic compounds in plants, animals or soils. This characteristic means that the availability of the element in the soil is high, and the release of potassium from plant components and animal waste is practically immediate when compared to the release of other nutrients (ASSMANN et al., 2017).
When recommending fertilization of systems, using the principles of nutrient cycling, nutrients can be applied in isolation, thus eliminating the need to use formulas. In the case of potassium, for example, in crop-livestock integration systems, it is recommended that fertilization of the system, both for the grazing phase and for the grain production phase of an agricultural year, be done in its entirety, with application at the time of planting the forage crop, using a fertilizer with a high potassium concentration as a source, such as potassium chloride (60% of K).2O) (ASSMANN et al., 2017).
The inclusion of grazing animals in an area of crop-livestock integration increases the efficiency of nutrient use, since the export of nutrients via animal products (meat, milk, and others) varies from 4 to 20% of the nutrients absorbed (Figure 2), which is much lower than the export observed in grain-producing crops. Thus, a large part of the fertilizers applied in the pasture phase of the crop-livestock integration system returns in the form of urine and feces. As long as the precepts of adequate grazing pressures are considered, these nutrients will return to the soil and will be available for absorption by the crop after the pasture phase (ASSMANN et al., 2017).
Figure 2. Proportion of nutrients N, P, K in the animal's body, exported in the form of milk and excreted in the form of urine and feces. Source: Source: ASSMANN & SOARES (2016).
FERTILIZATION RECOMMENDATIONS FOR SYSTEMS – PHOSPHORUS
Due to the presence of high levels of Al and Fe oxides-hydroxides in Brazilian soils and the phosphorus fixation power of these mineral fractions of the soil, it is normally recommended to apply the fertilizer in line when fertilizations are carried out via the application of acidulated phosphates (super simple, super triple, monoammonium phosphate, diammonium phosphate). Since these phosphates have a fast-release characteristic, if they were applied by broadcasting, the possibility of contact with the soil with the Al and Fe oxides-hydroxides would increase, which would result in the unavailability of the nutrient (ASSMANN et al., 2017).
FERTILIZATION RECOMMENDATIONS FOR SYSTEMS – NITROGEN
In the conception of Fertilization Systems, nitrogen, due to its close connection with the carbon cycle, is the chemical element that has the power to cause the greatest changes in nutrient cycling, not only on itself, but also affecting the cycling of other nutrients, as well as having a strong impact on the conservation of organic matter content in the soil (ASSMANN et al., 2017).
Precisely because of these characteristics and the wide variation in chemical forms in which nitrogen can be present in the soil, the recommendation for fertilization of this nutrient is quite complex. Currently, the recommendation for nitrogen fertilization is based on the levels of organic matter in the soil and whether the crop previously cultivated was a legume or a grass. However, possible reductions in the application of nitrogen fertilization resulting from higher levels of organic matter in the soil or because the previous crop was a legume are generally disregarded and producers end up applying a constant dose of nitrogen fertilizers (ASSMANN et al., 2017).
One way to assess the nutritional status of a crop in its initial growth stage is via nitrogen dilution curves. According to Lemaire (1997), when N concentrations in the aerial part of plants due to dry matter accumulation are above those calculated for C4 or C3 plants, these plants are well nourished and may be experiencing luxury consumption of the nutrient. On the other hand, if the N concentration is below this curve, the plants are probably undergoing a process of nutrient deficiency Assmann et al. (2017).
For Rhoden & Scherer (2022), due to the dynamics and complexity of N in the soil-plant-animal system, it is essential to maximize N cycling between the various components of the system, which occurs when the same N atom applied to the soil via chemical fertilizer, for example, urea, is solubilized and absorbed by the pasture and the grazing animals use this N in the production of meat or milk and this same N atom returns to the soil via feces and urine, and can temporarily be immobilized in the microbial biomass or absorbed by the pasture, and again under animal grazing, they can use this N which, subsequently, will return to the soil via feces and urine or plant residues, with the possibility of absorption, now, by subsequent crops. At this point, it can be stated that the cycling of N between the system components was efficient, allowing pasture production, animal weight gain and the production of subsequent grain crops, reducing the dependence on N from external sources, making the environment more sustainable, productive and balanced, corroborating greater efficiency in the use of N and fertilization of systems.
Therefore, System Fertilization constitutes a new paradigm for fertilization and liming in agricultural systems. This new system considers the soil as a single living organism, acting as the interface for the transfer of nutrients between agricultural crops. This new approach no longer considers the cycle of nutrients and toxic elements present in the soil solely from a mineral chemistry perspective, but instead interprets their behavior in association with soil biology. Soil management that seeks to build healthy soil will enhance the efficiency of the use of applied inputs, reducing production costs and environmental pollution (ASSMANN & SOARES, 2016).
As we have seen, in fertilization systems it is essential that nutrient cycling is efficient and that the use of these elements in these different systems is maximized, while maintaining soil health. Therefore, the use of more efficient fertilizers with low environmental impact becomes an indispensable practice to maintain the efficiency of the system.
ILSA BRASIL has a line of organomineral fertilizers (https://ilsabrasil.com.br/produtos/) that combine the organic matrix AZOGEL with mineral sources of nutrients. The presence of the AZOGEL matrix enhances the absorption of mineral nutrients, favors the microbiological activity of the soil and also provides 16 essential amino acids for plant metabolism. In addition, AZOGEL is rich in organic nitrogen that will be gradually made available to the system, increasing the use and reducing the losses of this nutrient. It has in its formulation organic acids that reduce the fixation of phosphorus in the soil and also has a high CTC, reducing the losses of cations such as calcium, magnesium and potassium.
Bibliographic references
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ASSMANN, Joice Mari et al. Soil carbon and nitrogen stocks and fractions in a long-term integrated crop–livestock system under no-tillage in southern Brazil. Agriculture, ecosystems & environment, v. 190, p. 52-59, 2014.
ASSMANN, TS; SOARES, André Brugnara. Migrating from crop fertilization to system fertilization through Crop-Livestock Integration. Informative integrate, 2016.
ASSMANN, Tangriani Simioni et al. Fertilization of Crop-Livestock Integration Systems. In: Lectures: intensification with sustainability. Brazilian Congress of Integrated Agricultural Production Systems. p. 67-84, 2017.
ASSMANN, TS; MARTINICHEN, D.; LIMA, RC; LEVINSKI-HUF, F.; ZORTEA, T.; ASSMANN, AL; MORAES, A.; ALVES, SA Fertilization of systems and nutrient cycling in integrated agricultural production systems. In: SOUZA, ED et al. (eds.) Integrated agricultural production systems in Brazil. 1st ed. Tubarão: Copiart, 2018.
BARCELLOS, T. Fertilization systems: how to achieve greater savings and high productivity. Lavoura, 2021.
BORTOLLI, MA Fertilization systems: anticipation of nitrogen fertilization for corn crops in crop-livestock integration. Thesis (Doctorate). Federal University of Technology of Paraná. Postgraduate Program in Agronomy, Pato Branco, 2016.
FREITAS, MR Forage production and animal performance in integrated agricultural production systems with fertilization systems in the cerrado. Dissertation (Master's degree). Federal University of Paraná. Postgraduate Program in Agronomy, Curitiba, 2021.
KLEINA, GB Microbial biomass and mineralizable carbon in soil in integrated agricultural production systems, 2018.
LEMAIRE, G. Diagnosis of the nitrogen status in crops. Berlin: Springer, 56 p., 1997.
MACCARI, M. Can canopy height and pasture nitrogen fertilization affect corn nitrogen nutrition in an integrated crop-livestock system? Thesis (Doctorate) - Federal Technological University of Paraná, Pato Branco, 2016.
RHODEN, Anderson; SCHERER, Guilherme Lucas. FERTILIZATION SYSTEMS AND CROP PRODUCTIVITY. Innovation Magazine: Management and Technology in Agribusiness, v. 1, n. 2, p. 51-69, 2022.
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SOARES, AB; AIOLFI, RB; DE BORTOLLI, MA; ASSMANN, TS and ZATTA, AC Animal and plant production in integrated agricultural production systems. In: Proceedings of the III Symposium on Animal Production on Pasture, NEPRU – Center for Teaching and Research in Ruminants, Dois Vizinhos, Paraná, 2015.
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Authors
- Agr Eng. Dr. Angélica Schmitz Heinzen
- Agricultural Eng. Msc. Carolina Custodio Pinto
- Agricultural Eng. Msc. Thiago Stella de Freitas
