Efficiency of phosphorus fertilizers: research results in long-term field experiments in Russia, Great Britain and China

<p>Long-Term Field Experiments (LTEs) are agricultural experiments for monitoring soil and crop properties in changing climate conditions and different management practices. These trials were set up on various soil textures and types to reveal the effects of management and environment on crop production and soil resources. Although the LTEs are essential infrastructures for sustainable soil yield and use, LTE-related information was dispersed, thus not easy to find. To close this research gap, we compiled and analyzed the meta-information of the LTEs across Europe and their spatial representation in a geospatial data infrastructure, including a data repository and an LTE overview map developed within the framework of the BonaRes project (BonaRes 2021; Grosse et al. 2021). During the research, LTEs with a minimum duration of 20 years were identified, and the meta-information was collected by extensive literature review and factsheets. In total, 405 LTEs in Europe were identified, clustered in different categories (management operations, land use, duration, status, etc.), and these clusters were geospatially analysed to provide inputs for the agricultural industry, scientists and decision-makers. LTEs from 25 countries were utilized including Germany, where the oldest LTE started in 1843. The majority of the LTEs have the fertilization treatment, followed by crop rotation and tillage. The results will help to develop a mutual agricultural management framework by revealing the LTE potential internationally. The geospatial data structure will contribute to scaling up the management practices from site to landscape-level for increasing the adaptation of agricultural systems to climate change.</p><p><strong>Key Words:</strong> Long-Term Field Experiments, BonaRes, Europe, soil science, GIS.</p><p>References</p><p>BonaRes (2021). Long-term Experiments in Europe. Overview of long-term Experiments. https://lte.bonares.de</p><p>Grosse, M., Ahlborn, M.C., Hierold, W. (2021). Metadata of agricultural long-term experiments in Europe exclusive of Germany. Data in Brief 38, https://doi.org/10.1016/j.dib.2021.107322</p><p> </p>

In field experiments with the long-term systematic application of fertilizers (prolonged trial), new regularities of the dynamics of the mobile phosphorus content in soils of various agroecosystems have been established. It is shown that the increase in the content of mobile phosphorus in different soils occurred only in the first rotation of crop rotations. In the future, despite the positive balance of phosphorus, the content of its mobile forms did not increase or even had a tendency to decrease due to the transition of phosphorus to an inactive state. In the case of a negative balance, the content of mobile phosphorus in soils was compensated by the reserve of inactive phosphates. Thanks to these processes of phosphate transformation in agricultural ecosystems supported the ecological balance, protecting against loss of phosphorus with surface and subsurface runoff of the element in the external environment and, thus, reduces the risk of water body eutrophication. The influence of phosphorus fertilizers on the biodiversity of soil microflora is also established. The dynamics of mobile phosphorus in various soils revealed in long-term field experiments can serve as a model of 2phosphorus transformation, which entered the soil from fertilizers in production conditions.

Precision crop production requires accurate yield prediction and nitrogen management. Crop simulation models may assist in exploring alternative management systems for optimizing water, nutrient and microelements use efficiencies, increasing maize yields. Our objectives were: (i) to access the ability of the CERES-Maize model for predicting yields in long-term experiments in Hungary; (ii) to use the model to assess the effects of different nutrient management (different nitrogen rates—0, 30, 60, 90, 120, and 150 kg ha−1). A long-term experiment conducted in Látókép (Hungary) with various N-fertilizer applications allowed us to predict maize yields under different conditions. The aim of the research is to explore and quantify the effects of ecological, biological, and agronomic factors affecting plant production, as well as to conduct basic science studies on stress factors on plant populations, which are made possible by the 30-year database of long-term experiments and the high level of instrumentation. The model was calibrated with data from a long-term experiment field trial. The purpose of this evaluation was to investigate how the CERES-Maize model simulated the effects of different N treatments in long-term field experiments. Sushi hybrid’s yields increased with elevated N concentrations. The observed yield ranged from 5016 to 14,920 kg ha−1 during the 2016–2020 growing season. The range of simulated data of maize yield was between 6671 and 13,136 kg ha−1. The highest yield was obtained at the 150 kg ha−1 dose in each year studied. In several cases, the DSSAT-CERES Maize model accurately predicted yields, but it was sensitive to seasonal effects and estimated yields inaccurately. Based on the obtained results, the variance analysis significantly affected the year (2016–2020) and nitrogen doses. N fertilizer made a significant difference on yield, but the combination of both predicted and actual yield data did not show any significance.

Chapter 8 - Geographical network: legacy of the Soviet era long-term field experiments in Russian agriculture

Long-term field experiments have been maintained by the Nicolae Dimo Institute of Pedology, Agrochemistry and Soil Protection for some 50 years. The long-term experiments on Grey forest soil (Phaeozem), Leached chernozem and Carbonate chernozem (Haplic and Calcic chernozem) that are now included in the EuroSOMNET Information Research System 2000 lend insights to the quality of arable soils under systematic application of fertilizers and support practical recommendations for soil management. Keys to this information are presented. Long-term field experiments should be continued in order to obtain new information on the optimization of soil properties, management regimes and increasing fertility by means of agro-technical and agrochemical measures.

Long-term field experiments are indispensable sources of knowledge. They are vitally important in monitoring, understanding and proving the changes in soil fertility occurring as a result of long-term agrotechnical operations, first of all that of fertilization. Because of longevity, it is fairly costly to maintain them. Their scientific and practical value is, however, immeasurable and keeps growing with their age. The information concerning the land use can not be replaced by other means. The oldest long-term experiments that have run continuously since their foundation are 160-years-old now. They were established at Rothamsted in England by the Rothamsted Experimental Station's founder J. B. Lawes and J. H. Gilbert in 1843. The scientific work of J. von Liebig, the German chemist, who drew up the theory of the increase of soil fertility, has also contributed to the foundation of the Rothamsted Classic Experiments to a large extent. In those days heated discussions about nutrient recycling incited the experimentation and scientific investigation. The experimentation in England has focused attention on long-term field experiments, and such experiments were soon set up in other lands too. In our days long-term experiments of more than 100 years can be found in six lands. These provide results characteristic first of all for the given site, however they concentrate attention on universally valid, surprisingly actual relations of cause and effect as well. These experiments are of great help to us to reconcile ecological and economic interests and to clear up actual questions of environmentally friendly nutrient supply and sustainable husbandry.

Biological and other soil parameters response to winter cover crops in a mediterranean irrigated system

Based on long-term (2016–2021) research results in a long-term stationary experiment (1971–2021) in the eastern district of the central climatic zone of the Kirov region, the influence of soil acidity and the content of mobile phosphorus on the yield and quality of grain crops and meadow clover when applying fertilizers (N90, N90P50K90) was estimated. It was found that the maximum yield (4.43 t/ha) in a long-term stationary experiment in the period 2016–2021 was obtained from Falenskaya 4 winter rye when N90P50K90 was applied to soil with pHKCl 3.8 and the content of mobile phosphorus in the soil was 121 mg/kg, which is 1.6 times higher than the “without fertilizers” option. The content of crude protein in the grain of cereals and the green mass of meadow clover was formed higher on the soil at pH 5.2–5.7 than at pH 3.7–4.0, did not depend on the content of mobile phosphorus in the soil, the application of fertilizers (N90, N90P50K90) for cereals increased the indicator by 1.60–5.96%. The indicator “grain nature” of cereal crops did not depend on the level of acidity and the content of mobile phosphorus in the soil, while the indicator exceeded the basic norm of standards for grain harvesting. The content of raw gluten in the grain of spring wheat varieties Iren and Bazhenka increased with the use of fertilizers by 4.0–14.8%. The maximum content (33.8 and 39.8%) was observed in the Iren variety on both acidic and cultivated soil with a mobile phosphorus content of 170–191 mg/kg when N90P50K90 was applied. The effect of fertilizers and the level of soil fertility on the indicator “falling number” in winter rye was insignificant.

Goal. To establish the regularities of dynamics of changes in the supply of basic nutrients at the systematic use of mineral fertilizers and after the cessation of their application. Methods. Statistical-mathematical analysis of observations on the content of mineral nitrogen, mobile phosphorus, and potassium in degraded chornozem of the stationary field experiment with fertilizers in 1970 -2020 on the territory of SE «SF Hrakivske» of NSC ISSA named after O.N. Sokolovskyi» (Kharkiv district, Kharkiv oblast). Results. Without the use of mineral fertilizers, the content of mineral nitrogen in the arable layer of the soil depends on the number of deposits and mostly corresponds to gradations of very low or low levels, and the content of mobile phosphorus and potassium corresponds to the limits of low and medium supply of these elements. With the systematic application of mineral fertilizers, the content of mobile phosphorus and potassium in the soil increases at the rate of 50 kg of the active substance (a.s.) per 1 ha with an intensity of 2.3 mg/kg per year and 1.2 mg/kg per year, at the rate of 100 kg a.s. per 1 ha — 3.1 mg/kg per year and 2.4 mg/kg per year, respectively. The consumption of phosphorus fertilizers to change the content of mobile P2O5 in the arable soil layer by 1 mg/kg depends on the duration of systematic fertilization and is 13.1-25.9 kg of P2O5 per 1 ha. The cost of potassium fertilizers to change the content of mobile K2O in the arable soil layer by 1 mg/kg is much higher than phosphorus and on average during the experiment was 49.5 kg a.s./ha. After the cessation of fertilizer application, there was a decrease in the content of mobile phosphorus in the soil in the first 10 years by 5.5 mg P2O5/kg per year, 20 years — by 4.8 mg P2O5/kg, for 30 years — by 4.1 mg P2O5/kg. The reduction of mobile potassium content in the soil after the cessation of fertilizer application is almost twice as fast as phosphorus. Conclusions. Using modeling of different levels of mobile phosphorus and potassium, the intensity of changes in the trophic state of the soil with the systematic application of mineral fertilizers under field crop rotation and after the cessation of fertilization. The estimated costs ic calculated of the active substance of phosphorus and potassium fertilizers to increase the content of mobile phosphorus and potassium by 1 mg/kg of soil, as well as the intensity of its reduction with extensive use of chornozem (without mineral fertilizers).

The changes of soil pH in long-term 14-year field experiments with different fertilizing systems are described. The field experiments were located at four sites of the Czech Republic with different soil and climatic conditions (ČervenĂ˝ Újezd, Hněvčeves, Lukavec, and Prague-Suchdol). At each site, the same fertilizing systems and crop rotation (potatoes - winter wheat - spring barley) were established. Six experimental treatments were applied to crop rotation: (1) unfertilized treatments (control); treatments with organic fertilization: (2) farmyard manure (FYM), (3) sewage sludge (SS); treatments with mineral fertilizers: (4) nitrogen (N), (5) nitrogen with straw application (N + straw), and (6) nitrogen with phosphorus and potassium (NPK). The long-term effect of fertilizers significantly depends on soil conditions. At the site Prague-Suchdol minimal differences in the soil pH were observed by all treatments. This is caused by the high buffering capacity of Chernozems against the soil acidification. At ČervenĂ˝ Újezd (Haplic Luvisol), Hněvčeves (Haplic Luvisol), and Lukavec (Stagnic Cambisol) sites, soil pH decreased by all treatments. Only at Hněvčeves site the soil pH did not change with N treatment. The highest soil pH decrease in the treatment with NPK (ΔpH -0.89) and N + straw (ΔpH -0.70) was observed at Hněvčeves site. By the treatments FYM and SS the highest decrease was registered at ČervenĂ˝ Újezd (ΔpH of about -0.30 and -0.63, respectively). The highest decrease in control treatment (ΔpH of about -0.63) was observed at Lukavec site. The results showed that to evaluate long-term soil pH changes a whole complex of factors must be examined.

Enhanced seed yield of full-season soybean when rotated with cereals and cover crops as compared to monoculture in a long-term experiment

The aim is to study the influence of different types of postharvest green manure crops on soil fertility indicators. The research was supposed to study the effect of growing postharvest greens: winter wheat, spring barley, peas and winter oilseed rape on soil fertility: humus content, alkaline hydrolyzed nitrogen, mobile phosphorus, exchangeable potassium, soil reaction and soil acidity. Experimental studies were conducted during 2018–2021 in the conditions of FG "Zorya Vasylivka" Tyvriv district of Vinnytsia region on gray podzolic soils. In the option without growing greens, the humus content was 2.30%. Growing green manures contributed to the increase of humus content in the soil during crop rotation by 0.11–0.14%. The content of humus increased the most in the variant of growing green peas and winter rape, and the least — in spring barley. In general, the highest humus content was found in the variant of growing green peas and winter rape — 2.44%, and the lowest — in the cultivation of spring barley green — 2.41%. The alkaline nitrogen content in the option without growing greens was 118 mg/kg. When growing greens, the content of alkaline hydrolyzed nitrogen in the soil increased by 1.7–7.1%. The alkaline nitrogen content in the option without growing greens was 118 mg/kg. When growing greens, the content of alkaline hydrolyzed nitrogen in the soil increased by 1.7–7.1%. The content of alkaline hydrolyzed nitrogen in the soil increased the most after growing green peas, and the least after spring barley and winter rape. The highest content of alkaline hydrolyzed nitrogen was found in the soil where green peas were grown — 127 mg/kg, and the lowest — after growing green barley green manure and winter rape — 120 mg/kg. The concentration of mobile phosphorus in the control variant without growing greens was 622 mg/kg and was the highest among all studied variants where greens were grown. In the variants with the cultivation of green manure crops, the content of mobile phosphorus in the soil decreased by 16.4–18.0%. The smallest decrease in the content of mobile phosphorus in the soil, compared to the option without the use of green manure, was found in the variant of growing green wheat green manure, and the largest decrease — in the variant of growing green barley green manure. The soil of the variant without growing green manure contained exchangeable potassium 156 mg/kg. The cultivation of greens contributed to the increase in the content of exchangeable potassium in the soil by 27.4–32.2%. The largest increase in the content of potassium exchange in the soil was found in the variant of growing winter rape green manure, and the smallest — in the cultivation of winter wheat. The reaction of the soil pH on the option without growing greens was 6.05 pH. Variants with green manure cultivation were marked by a decrease in the reaction value of the soil solution by 0.2–0.5 pH. This indicates acidification of the soil when growing greens. The greatest acidification of the soil is observed after growing green rape green manure, and the least — after spring barley green manure. The hydrolytic acidity of the soil in the variant without green manure cultivation and in the cultivation of winter wheat green manure was the same and amounted to 1.60 mg-eq./100 g. In other variants of green manure cultivation, the hydrolytic acidity of the soil increased by 3.0–7.0%. The largest increase in hydrolytic acidity was found in the variant of growing winter rape green manure, where the actual hydrolytic acidity of the soil was the highest and amounted to 1.72 mg-eq./100 g.

The soil organic matter (SOM) content and quality are the fundamentals of soil fertility and contribute significantly to soil carbon sequestration. The soil glomalin content is increasingly recognized as an indicator of SOM quality. The objective of this study was to evaluate the capability and contribution of the easily extractable glomalin (EEG), total glomalin (TG) content, potential wettability index (PWI) of soil aggregates, and water stability of soil aggregates (WSA) as instrumental indicators of long-term SOM quality changes. The obtained results on EEG, TG, PWI, and WSA were compared to the results of humic substances fractionation, specifically their relationship to carbon in humic substances, humic acids, and fulvic acids (CHS, CHA, and CFA, respectively). We used long-term field experiments (27 years) with a simple crop rotation starting with potatoes (site A) or maize (site B), followed by winter wheat and spring barley (on both sites) on the luvisol soil type. Fertiliser treatments were based on the application of uniform 330 kg N ha-1 per three years. Treatments were as follows: unfertilised control (Cont), sewage sludge in normal and triple dose (SS1 and SS3, respectively), farmyard manure in the conventional dose and half dose with mineral nitrogen (F1 and F1/2+N1/2, respectively), straw and mineral N fertiliser (N+St), and mineral N only (N). For the evaluation of the fertiliser effect, data from both sites were pooled together. The farmyard manure application in the F1 treatment showed the best potential for improving the SOM quality (the highest CHA, humification rate, humification index, TG content, and WSA). The results of Cont treatment show degradation of SOM content and quality. No significant effect of fertiliser treatment on the EEG was observed. The TG content was significantly influenced by fertiliser in the F1, F1/2+N1/2, and SS3 treatments (1965, 1958, and 1989 mg kg-1, respectively) in comparison with the Cont (1443 mg kg-1). The TG content was in a tight relationship with the CHA content (R2 = 0.298; p<0.001). The PWI was also influenced by the treatment. There was a significant positive relationship between PWI and CHS (R2 = 0.550), CHA (R2 = 0.249), and CFA (R2 = 0.492), p<0.001. No significant relationship was established between the WSA and SOM quality indicators. Both TG content and PWI can be used as indicators of SOM quality in long-term experiments. On the other hand, the EEG content and WSA are not capable of determining the changes in the SOM quality.

Long-term experiments like those at Rothamsted in southeast England offer the best practical means of studying the effects of land management or global change on soil fertility, sustainability of yield or wider environmental issues. For the data from such experiments to be of use, farmers, scientists and policy makers must be certain of their validity. This is best assured by the rigorous management of the experiment, by ensuring that any changes are carefully considered and that all operations are well-documented. A steady flow of well-interpreted, published data is also essential. This paper gives examples of how the long-term field experiments at Rothamsted have been managed and how modifications have been made to ensure their relevance to modern agriculture. Key words: Rothamsted, sustainability, long-term experiments, global change

The scientific management of salinized agricultural lands and the use of undeveloped saline lands to ensure food security have become one of the most urgent tasks nowadays. Biochar contains rich carbon (C) and functional groups, and processes high alkalinity, porosity, and specific surface area (SSA). Thus, it has been widely used as an effective organic conditioner in acidic or neutral soils to improve their fertility. However, so far, the impacts of biochar application on properities of saline soils and the underlying mechanisms remain unveiled. Therefore, in this study, we focus on the investigation of the impacts of biochar on the physical, chemical, and biological properties of saline soils. We found that biochar could: (1) decrease soil bulk density (BD), increase soil porosity, promote the formation of soil aggregation and enhance the leaching of soil salts; (2) increase the cation exchange capacity (CEC) of soil, decrease the salinity of soil through ion exchange and adsorption; (3) directly act as the nutrient supplements, indirectly adsorb water and nutrients or improve nutrient availability (e.g., soil organic carbon (SOC) turnover and sequestration, nutrient cycling); and (4) improve the structure and functioning of the soil microbial community and therefore indirectly impact the C, nitrogen (N) and phosphorus (P) cycling in soil systems. However, these impacts heavily depend on the properties, the concentration of the biochar added to the soil, and the type and location of the soil. In fact, some studies have shown that the addition of biochar in soil could even increase the salinity of saline soils. Another issue is the lack of long-term and large-scale field experiments regarding the impact of biochar addition on properties of saline soils. Therefore, future studies should focus on long-term field experiments with the combination of traditional soil analytical methods and mordern molecular techniques (e.g., high-throughput sequencing, macro-genomics, and metabolomics) to comprehensively reveal the response mechanism of physicochemical properties and microbial characteristics of saline soils to exogenous biochar. Our study can provide a scientific foundation for the practical agricultural production and ecological management of biochar.