How to maintain soil fertility in stockless organic farming: Research concepts and insights from the first crop rotation of a long-term field experiment

Biochar, compost and biochar-compost: effects on crop performance, soil quality and greenhouse gas emissions in tropical agricultural soils

Agronomic management practices shape soil health and crop productivity in northeastern China: Insights from a meta-analysis

The major issue in modern agriculture is long-term sustainability. Nutrient management by integrating organic manures and inorganic fertilizers may play a vital role in improving and sustaining crop productivity. A long-term field experiment (since 1984) comprising 11 treatments with different combinations of inorganic and organic fertilizers such as farm yard manure (FYM), wheat cut straw (WCS) and Dhaincha (Sesbania aculeata L.) as green manure (GM) was conducted to evaluate their effects on crop yield, nutrient accumulation and soil fertility status under a rice – wheat cropping system. The maximum grain yield of wheat was recorded in T6, i.e. 50% recommended dose of fertilizers (RDF) + 50% nitrogen through FYM in rice and 100% RDF in wheat (4291 kg ha−1) as compared to chemically fertilized plots T5, i.e. 100% RDF in both rice and wheat (3441 kg ha−1). The application of organic manures in combination with chemical fertilizers reduced soil pH and bulk density from 7.40 to 7.23 and 1.49 to 1.37 g cm−3, respectively. Soil organic carbon (SOC), available soil nutrients and nutrient accumulation by crop were higher in integrated nutrient management-treated plots as compared to control. A positive and significant correlation was observed between SOC and available soil nitrogen (r = 0.987), phosphorus (r = 0.913) and potassium (r = 0.921). The results clearly suggest that integrated use of chemical fertilizers and organic manures on a long-term basis improves soil fertility and crop productivity with the potential to enhance soil sustainability

There are several important differences between organic and conventional biogas production. One difference concerns the biomass production system (e.g., legume-grass instead of maize), and another difference is the way in which biogas plants are integrated into nutrient cycles, which results in different effects on soil fertility, crop yields, and the environment. The focus of this study is an analysis of the yield response and economic impact of biogas plant integration into an organic arable farming system. We compare two organic farming systems: the reference system (an arable farming system without biogas production) and the biogas system (an arable farming system with biogas production). Both farming systems underwent the same crop rotation, and the cash crops produced in the biogas system were sold identically to those in the reference system. In the reference system, the grass–legume mixture of the green fallow was mulched and left as green manure on the fields. In the biogas system, the grass–legume mixture was used for biogas production; therefore, electricity, heat, and the biogas slurry for fertilization of the cash crops were produced. The comparisons are based on a long-term field experiment and additional modeling data. This research approach was chosen to achieve reliable results on the basis of measured yield effects under comparable site and management conditions. Within the investigated period (2010–2014), the cereal yields of the biogas system were significantly (27–47%) higher than those of the reference system (arable farming). Case studies and model calculations on the basis of the experimental data showed higher entrepreneurial profits from the biogas systems as a result of the yield effects. The entrepreneurial profit of the arable farming in the biogas system was approximately 300 € ha−1 higher than that of the reference system. The higher revenues from the cash crops also compensated for the financial losses induced by the biogas plants. The dimensions of a biogas plant are important for improving the overall profit of a farm; the size must be adapted to the on-site supply of substrates and the need for biogas slurry. This study shows that suitable organic biogas production leads to synergistic effects between bioenergy and food production. The integration of a biogas plant into an organic farming system can ensure energy supply while increasing food output.

Six-year transition from conventional to organic farming: effects on crop production and soil quality

Organic farming may improve agroecosystems’ resilience against external stressors, favour below-ground biodiversity, soil health, and increase soil water holding capacity. At the same time, organic farming systems are repeatedly reported to have lower average crop yields than conventional systems. To date, global meta-analyses on organic farming systems include a diverse range of crops, but none of them specifically focus on arable systems with cereal-based rotations. Further, they are not representative for specific European agro-environmental zones and often show weaknesses in the applied meta-analytical methodology.This meta-analysis aimed at quantitatively summarizing existing knowledge and outcomes on soil organic carbon (SOC) in the topsoil (0-20/30 cm) and cereal production (i.e., yields and yield stability) in organic farming systems compared to conventional farming systems across Europe.The database consisted of 43 independent field studies on SOC and 50 field studies on cereal yields across 16 European countries, covering nine European agro-environmental zones. Cereal-based rotations were cultivated organically and conventionally on mineral soils, up to several decades. Yields for winter rye, winter and spring wheat, spring barley and spring oats were annually measured. SOC was measured as stock or concentration at the end of the experiments. Organic farming systems relied either on animal-based or plant-based fertilizers, or on both sources of nitrogen input. Conventional systems received solely mineral fertilization in most experiments. For both farming systems conventional tillage was applied without irrigation. The meta-analysis was conducted by using Meta Win 2.0 and IBM SPSS Statistics 29. As an index of effect size, we used ln (R), i.e., relative SOC, yield or temporal yield variation.  All studies were weighted by inverse variance.The overall effect of organic farming was a 5% increase of topsoil SOC (95% CI: 1% – 9%, n=43) compared to conventional systems. Pedoclimatic factors, such as mean annual precipitation and clay content had a profound impact on SOC response under organic farming (p=0.014). With increasing annual precipitation and clay content, SOC response to organic farming was increasing, and reached 20% in areas with clayey soils and annual precipitation of 700 mm. In addition, the response of SOC to organic farming showed some positive trend with increasing soil pH (p=0.059).Overall, cereal yield in organic farming was about 30% lower compared to conventional farming systems. However, yield performance of organic systems varied statistically significantly across farming types (p=0.021): a 20% yield gap was observed in organic systems using animal-based fertilizers, while a 35% yield gap was shown in organic systems using only legumes or mixed green manure. Moreover, the yield gap decreased with increasing average annual temperature (p=0.002). Overall, the temporal yield variation of organic farming systems was about 50% larger than in conventional systems, which was not related to any pedoclimatic factors studied.In conclusion, organic farming systems had a positive impact on SOC in the topsoil, compared to conventional systems. The magnitude of this influence mainly depended on pedoclimatic characteristics in Europe. In terms of cereal production, organic farming had lower yields and yield stability compared to conventional farming.

No-tillage (NT) and reduced tillage (RT) systems are well-known management tools for reducing soil erosion and improving soil fertility. NT and RT may improve the environmental and economic performance of organic farming, but they are still not common practice among organic farmers. This paper presents the effects of tillage [RT versus conventional tillage (CT)], fertilization (slurry versus manure compost) and biodynamic preparations (with versus without) on soil fertility indicators such as soil organic carbon (Corg), microbial biomass and microbial activity, soil nutrients and nutrient budgets in an organic farming system during the first six-year crop rotation period of a long-term experiment on a clayey soil in a temperate climate. RT caused stratification of soil organic carbon (Corg), microbial properties and soil nutrients in the soil profile. Under RT, Corgin the 0–10 cm soil layer increased from 2.19 to 2.61% (w/w) from 2002 to 2008, whereas it remained constant under CT. In both tillage treatments, Corgremained constant in the 10–20 cm soil depth. Microbial biomass C increased by 37% under RT in the 0–10 cm soil depth and microbial activity [dehydrogenase activity (DHA)] was enhanced by 57%. Soil microbial biomass C and DHA in the 10–20 cm soil depth were also higher under RT (+10 and +17%, respectively). Soluble soil P and K were 72 and 40%, respectively, higher in 0–10 cm soil depth under RT when compared with CT. Fertilization showed no effects on the measured soil properties. Biodynamic preparations increased solely the Cmic-to-Nmic(soil microbial biomass C to soil microbial biomass N) ratio by 7% in the 0–10 cm soil depth. Nutrient budgets for P were balanced in all treatments, but N and K exports were higher under RT compared to CT. We conclude that RT is a suitable method for increasing indicators of soil fertility in organic farming systems. The combined effects of RT and an organic farming system with a diverse, ley-based crop rotation and organic fertilization merit further promotion and it may be considered for supporting actions by the agricultural policy schemes.

Changes in land‐use and agricultural management affect soil organic C (SOC) storage and soil fertility. Grassland to cropland conversion is often accompanied by SOC losses. However, fertilization, crop rotation, and crop residue management can offset some SOC losses or even convert arable soils into C sinks. This paper presents the first assessment of changes in SOC stocks and crop yields in a 60‐year field trial, the Zurich Organic Fertilization Experiment A493 (ZOFE) in Switzerland. The experiment comprises 12 treatments with different organic, inorganic and combined fertilization regimes. Since conversion to arable land use in 1949, all treatments have lost SOC at annual rates of 0.10–0.25 t C ha−1, with estimated mean annual C inputs from organic fertilizers and aboveground and belowground plant residues of 0.6–2.4 t C ha−1. In all treatments, SOC losses are still in progress, indicating that a new equilibrium has not yet been reached. Crop yields have responded sensitively to advances in plant breeding and in fertilization. However, in ZOFE high yields can only be ensured when mineral fertilizer is applied at rates typical for modern agriculture, with yields of main crops (winter wheat, maize, potatoes, clover‐grass ley) decreasing by 25–50% when manure without additional mineral fertilizer is applied. ZOFE shows that land‐use change from non‐intensively managed grassland to cropland leads to soil C losses of 15–40%, even in rotations including legumes and intercrops, improved agricultural management and organic fertilizer application.

Nitrogen (N) is the most important yield-limiting factor in agricultural systems, however, N application can lead to emissions and environmental problems such as global warming (N2O) and groundwater contamination (NO3 −). This study analyses the N balance, nitrogen-use efficiency, and N loss potential of conventional farming systems (arable farming, improved arable farming, and agroforestry) and organic farming systems (mixed farming, arable farming, and agroforestry) based on long-term field experiments in southern Germany. The effects of the conversion of farm structure and N management are identified. The conventional farming systems in this study were high N-input and high N-output systems. The conventional arable farming system had the lowest nitrogen-use efficiency and the highest N surplus. An optimised N management and the use of high-yielding crop varieties improved its nitrogen-use efficiency. The establishment of conventional agroforestry resulted in the reduction of N input, N output and N surplus, while maintaining high yields. The organic mixed farming system is characterised by a relatively high N input and N output, the accumulation of soil organic nitrogen, the highest nitrogen-use efficiency, and the lowest N surplus of all analysed systems. These good results can be attributed to the intensive farm N cycle between soil–plant–animal. The shift from organic mixed farming to organic arable farming system extensified the N cycle, reduced N input, crop yield and N output. The change from organic arable farming to organic agroforestry reduced the N input, increased the biomass yield, and remained the N surplus within an optimal range.

The objective of the chapter is to assess the impact of long-term fertilization on biologically active substances in arable Fragic Glossic Retisols and to compare received results with corresponding native forest soil. The analysis of interactions of chemical and biochemical compounds in soils was based on soil samples taken from the long-term field experiment (crop rotation, as cultivated ecosystem, with application of mineral and organic fertilizers: potato, spring wheat, spring barley) and from the forest soil (as native ecosystem). The relationship between quantities of chemical and biochemical compounds in arable soils’ organic matter and in the yield of cultivated plants was greatly influenced by the use of mineral and organic fertilizers. The contents of phytohormone indole-3-acetic acid (IAA), participating in nitrogen cycle enzymes (urease and nitrate reductase), and different forms of nitrogen and organic carbon in soils have a marked effect on the crop yield. Arable soil in rotation without organic fertilizers treated with mineral fertilizer (120 kg N ha−1) revealed the highest increase of nitrate reductase activity, and the highest concentration of IAA, however, the lowest activity of urease. Therefore, mineral fertilizer in comparison with farmyard manure and alternative organic fertilizers created the most suitable conditions for the crop yield increase. The highest activity of urease in forest soil is closely associated with the concentration of biochemically available (dissolvable in water) organic carbon.

Balanced and integrated use of organic and inorganic fertilizers may enhance the accumulation of soil organic matter and improves soil physical properties. A field experiment having randomized complete block design with four replications was conducted for 36 years at Punjab Agricultural University (PAU), Ludhiana, India to assess the effects of inorganic fertilizers and farmyard manure (FYM) on soil organic carbon (SOC), soil physical properties and crop yields in a maize (Zea mays)–wheat (Triticum aestivum) rotation. Soil fertility management treatments included were non-treated control, 100% N, 50% NPK, 100% NP, 100% NPK, 150% NPK, 100% NPK + Zn, 100% NPK + W, 100% NPK (-S) and 100% NPK + FYM. Soil pH, bulk density (BD), electrical conductivity (EC), cation exchange capacity, aggregate mean weight diameter (MWD) and infiltration were measured 36 years after the initiation of experiment. Cumulative infiltration, infiltration rate and aggregate MWD were greater with integrated use of FYM along with 100% NPK compared to non-treated control. No significant differences were obtained among fertilizer treatments for BD and EC. The SOC pool was the lowest in control at 7.3 Mg ha−1 and increased to 11.6 Mg ha−1 with 100%NPK+FYM. Improved soil physical conditions and increase in SOC resulted in higher maize and wheat yields. Infiltration rate, aggregate MWD and crop yields were positively correlated with SOC. Continuous cropping and integrated use of organic and inorganic fertilizers increased soil C sequestration and crop yields. Balanced application of NPK fertilizers with FYM was best option for higher crop yields in maize–wheat rotation.

Soil organic carbon is affected by organic amendments, conservation tillage, and cover cropping in organic farming systems: A meta-analysis

In 1998, the Organic Arable Farming Experiment Gladbacherhof (OAFEG) was started in order to explore the impact of different organic arable production systems (mixed farming, stockless farming with rotational ley, stockless cash crop farming) and of different tillage intensities (conventional plough as a full inversion tillage, two-layer plough, inversion tillage at reduced depth, non-inversion tillage) on sustainability parameters. In this article, we present results on the development of soil organic matter (SOM) levels. Starting with organic mixed farming with approximately 0.7 livestock units (LU) per ha cattle before set-up of the experiment, only the mixed farming system in the experiment was able to maintain SOM levels. The stockless system with ley maintained soil organic carbon (SOC), but lost soil total nitrogen (STN), and the stockless cash crop system had a significant SOM loss in the magnitude of 7.7 t SOM ha−1, or roughly 8.4% of the initial SOM mass. Reducing tillage intensity had no impact on SOM masses, but only on organic matter stratification in soils. We conclude that specialization of organic farms towards stockless arable crop production requires special attention on SOM reproduction to avoid detrimental effects. Further, reduced tillage intensity does not necessarily have a positive effect on SOM.

Fertilization can significantly affect the quality of crop and soil. To determine the effects of long-term fertilization on crop yield and carbon:nitrogen:phosphorus (C:N:P) stoichiometry in soil, a study was conducted on the terraced fields of the Loess Plateau from 2007 to 2019. Nine fertilization treatments were included: no fertilizer; organic fertilizer (O); organic and nitrogen fertilizers (ON); organic, nitrogen, and phosphorus fertilizers (ONP); organic and phosphorus fertilizers (OP); phosphorus and nitrogen fertilizers; potash and nitrogen fertilizers; potash, nitrogen, and phosphorus fertilizers; and potash and phosphorus fertilizers. Under these treatments except for CK and PK, crop yields initially decreased but later increased. The nutrient content and C:N:P stoichiometry increased in soil depth of 0–20 cm. The soil available nutrients did not change significantly with the duration of fertilization. The O, ON, ONP, and OP had the most evident effect on the enhancement of soil nutrient content, whereas O and ON had the most evident effect on the increase in soil organic carbon (SOC):total phosphorus (TP) and total nitrogen (TN):TP. In soil depth of 0–20 cm, crop yield, SOC:TN, SOC:TN, SOC:TP, and TN:TP significantly correlated with soil nutrients. This study indicated that long-term fertilization can effectively improve crop yield, soil fertility, and soil C:N:P stoichiometry. Meanwhile, the single application of an organic fertilizer or the combination of organic and nitrogen fertilizers can improve the condition of nitrogen limitation in arid and semi-arid areas.

A long-term field experiment was conducted under rainfed conditions at the research farm of Banaras Hindu University (BHU), Varanasi, Uttar Pradesh, India, to assess the long-term effects of inorganic and organic fertilizer applications on crop yield and soil carbon dynamics in a rice–lentil cropping system. The 12-year study (2005–2017) was laid out in a randomized block design with eight treatments comprising different combinations of inorganic fertilizers and farmyard manure (FYM), applied to rice during the kharif season and lentil during the rabi season. The objective was to evaluate the influence of these nutrient management practices on crop productivity, soil organic carbon (SOC), soil microbial carbon, and their potential for carbon sequestration. Results indicated that full i.e. 100% replacement and partial substitution (50%) of chemical nitrogen (50% N) with FYM, as well as the combined application of FYM and inorganic fertilizers, significantly enhanced rice yield compared to only chemical fertilizer application. Higher nutrient input levels led to greater improvements in crop yield and SOC accumulation. A strong positive correlation was observed among crop yield, SOC, and soil microbial carbon content (SMC), highlighting that integrated nutrient management practices enhance both soil carbon sequestration and system productivity. The study concludes that the combined use of organic and inorganic fertilizers is a sustainable strategy for maintaining soil health and improving productivity in rainfed rice–lentil systems.