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The management of climate-resilient grassland systems is important for stable livestock fodder production. In the face of climate change, maintaining productivity while minimizing yield variance of grassland systems is increasingly challenging. To achieve climate-resilient and stable productivity of grasslands, a better understanding of the climatic drivers of long-term trends in yield variance and its dependence on agronomic inputs is required. Based on the Park Grass Experiment at Rothamsted (UK), we report for the first time the long-term trends in yield variance of grassland (1965–2018) in plots given different fertilizer and lime applications, with contrasting productivity and plant species diversity. We implemented a statistical model that allowed yield variance to be determined independently of yield level. Environmental abiotic covariates were included in a novel criss-cross regression approach to determine climatic drivers of yield variance and its dependence on agronomic management. Our findings highlight that sufficient liming and moderate fertilization can reduce yield variance while maintaining productivity and limiting loss of plant species diversity. Plots receiving the highest rate of nitrogen fertilizer or farmyard manure had the highest yield but were also more responsive to environmental variability and had less plant species diversity. We identified the days of water stress from March to October and temperature from July to August as the two main climatic drivers, explaining approximately one-third of the observed yield variance. These drivers helped explain consistent unimodal trends in yield variance—with a peak in approximately 1995, after which variance declined. Here, for the first time, we provide a novel statistical framework and a unique long-term dataset for understanding the trends in yield variance of managed grassland. The application of the criss-cross regression approach in other long-term agro-ecological trials could help identify climatic drivers of production risk and to derive agronomic strategies for improving the climate resilience of cropping systems. [ABSTRACT FROM AUTHOR]

Background: The use of renewable energy for sustainable and climate-neutral electricity production is increasing worldwide. High-voltage direct-current (HVDC) transmission via underground cables helps connect large production sides with consumer regions. In Germany, almost 5,000 km of new power line projects is planned, with an initial start date of 2038 or earlier. During transmission, heat is emitted to the surrounding soil, but the effects of the emitted heat on root growth and yield of the overlying crop plants remain uncertain and must be investigated. Results: For this purpose, we designed and constructed a low-cost large HeAted soiL-Monolith (HAL-M) model for simulating heat flow within soil with a natural composition and density. We could observe root growth, soil temperature and soil water content over an extended period. We performed a field trial-type experiment involving three-part crop rotation in a greenhouse. We showed that under the simulated conditions, heat emission could reduce the yield and root growth depending on the crop type and soil. Conclusions: This experimental design could serve as a low-cost, fast and reliable standard for investigating thermal issues related to various soil compositions and types, precipitation regimes and crop plants affected by similar projects. Beyond our research question, the HAL-M technique could serve as a link between pot and field trials with the advantages of both approaches. This method could enrich many research areas with the aim of controlling natural soil and plant conditions. [ABSTRACT FROM AUTHOR]

• Impact ranking of mineral fertilizer on production risk and yield stability: N > K > P. • Decreasing time trend of the production risk because of the mineral supply of NPK. • Production risk decreased over time because of additional manure supply. • Full mineral NPK supply with manure ensured the highest and most stable yields. • Lowest and most unstable yields occurred in the non-fertilized systems. The objective of our analysis was to demonstrate a novel application of production risk (probability of a yield falling below a certain level) and yield stability analysis based on the totalized yield across a 'sugar beet–winter wheat–spring barley´ crop rotation. We evaluated a long-term experiment spanning more than 60 years regarding the effect of mineral NPK fertilization and the additional supply of manure on the production risk, the risk development over time (trend), and the stability of biomass yields. We found that positive impacts such as reduced production risk and enhanced yield stability were the highest for the mineral N supply, were intermediate for the K supply, and were the lowest for the P supply. The full amount of the mineral nutrient fertilization, particularly in combination with an additional manure supply, resulted in lower production risk and more stabilized crop rotational yields compared to one-half the amount of nutrient supply. The mineral fertilization of NPK (at one-half and a full amount) led to a decreasing risk trend, particularly with the additional manure supply. The risk trend of the variants with P and K (but without N) or even no mineral nutrient fertilization only decreased over time with the manure supply. The lowest production risk and the best combination of high and stable yields of the crop rotation were found at full mineral NPK fertilization in addition to manure. In contrast, the highest production risk and the worst combination of the lowest and most unstable yields were obtained under a fertilization regime without N or even under nonfertilized management. The production risk and yield stability of this fertilization regime could be reduced via regular manure application carried out once per three-year rotation during the experimental period. [ABSTRACT FROM AUTHOR]

The current study is based on a long-term field experiment that was conducted at the Rauischholzhausen field station of the University of Giessen (Germany). It includes six different crop rotation systems (CRSs), three mineral nitrogen (N) fertilization treatments and the varying annual weather conditions (AWCs) over 25 years (1993-2017). To ensure new insight into wheat cropping systems that have high yield stability, the dataset was assessed using different methods of stability analysis, including eco-valence, biplot and risk analysis. The results show that the factors which influence grain yield variation in winter wheat can be ranked in the following order: (1) N fertilization; (2) AWC; and (3) CRS. Compared to winter rye as the preceding cereal crop, field bean as the preceding legume crop had a clearly positive effect on the grain yield stability of winter wheat. Furthermore, the higher N fertilization level led to more stable grain yields of winter wheat for all investigated CRSs. Overall, in this study, crop rotation and N fertilization had a high impact on the yield stability of winter wheat. These are important factors to consider in agronomic management decisions under the increasingly difficult environmental conditions caused by climate change. [ABSTRACT FROM AUTHOR]

Highlights • Higher mineral N fertilisation led to more stable wheat yields. • Mineral P and K supply resulted in minor effects on yield stability of wheat. • Additional application of manure has a stabilising effect on wheat yields. Abstract It is well known that a balanced nutrient supply ensures high crop yields and stable cropping systems. In comparison, little is known about the influence of different fertilisation regimes on the yield stability of crops. Therefore, the objective of this study was to identify the impact of mineral and organic fertilisation supplied in different combinations (P + K/N + P/N + K/N + P + K) and levels (50%/100%/100% + manure) on the stability of the winter wheat grain yield. A long-term fertilisation field experiment at Giessen University (Germany, temperate climate, silty clay), established in 1956 with a multifactorial set up, was used. For an accurate stability analysis that matches the experimental design, we subjected the data to a mixed model analysis based on the restricted maximum likelihood (REML) method calculating Shukla's stability variance and Finlay–Wilkinson regression and performing Eskridge's risk analysis. It was found that without any nutrient supply, the wheat yields exhibited high annual variability and only modest stability. A similar pattern was identified for the fertiliser combination of the minerals P + K. The combinations containing mineral N showed a significant improvement in yield stability in which N + P and N + K are almost identical. In all fertilisation variants, the additional supply of manure stabilised the wheat yields. The mineral supply of N + P + K with additional manure provided the best yield stability and lowest agronomic risk for yield failure. [ABSTRACT FROM AUTHOR]

High productivity and yield stability over time in combination with a reduction in the crop failure risk are the principal goals of both conventional and organic agriculture. These goals are achieved in organic agriculture through the maintenance of soil fertility and soil functions through agronomic practices such as balanced crop rotations and the application of organic amendments. Reduced tillage constitutes an important practice that limits the disturbance to the soil structure and biota, but deep ploughing is frequently used in organic farming for weed control and aeration of heavy soils. This study aimed to assess the impact of mixed organic farms and farms without livestock, so called stockless farms, with their respective crop rotations and fertilization management, and the effect of reduced tillage on yield dynamics. We compared yield dynamics i.e., crop yield, yield stability and the production risk, of three organic farming systems involving four levels of tillage intensity each at the Organic Arable Farming Experiment Gladbacherhof (OAFEG), Germany, based on a long-term (24 year) dataset. The six-year crop-rotation of a mixed farm was compared to stockless farming with rotational alfalfa ley and stockless farming with cash crops. The levels of tillage intensity ranged from deep inversion ploughing to non-inversion tillage. The yield data from the OAFEG trial were evaluated with respect to the mean yield data from all cropland systems at Gladbacherhof research farm. We calculated the yield dynamics of the complete crop rotation as well as three crops within the rotations i.e., winter wheat, winter rye and potato. The most promising combination of high yield and yield stability was mixed farming with deep (30 cm) and shallow (15 cm) ploughing, in contrast to stockless farming (with ley) with non-inversion tillage. Similar results were recorded for cereals, but not for potatoes. Stockless farming with cash crops and non-inversion tillage had the highest production risk, i.e., the highest probability of falling below the defined critical yield level. Under the predominant heavy soil conditions in central Germany, non-inversion tillage can't keep up with inversion tillage regarding a stable organic production. Mixed farming with livestock which is representative of traditional organic farming system was found to produce high yields, but also stockless farming with rotational alfalfa ley was competitive. Stockless or "vegan" organic farming can be an alternative production system to organic mixed farming with stable yields provided that rotational alfalfa ley is part of the crop rotation. Ploughing depth can be reduced without affecting productivity. [Display omitted] • Stockless farming with ley and inversion ploughing shows high and stable yield. • Shallow ploughing is a promising alternative to deep ploughing in respect to yields. • Worst yield dynamics with non-inversion tillage in all farming systems. • Farming system and tillage affect yield of winter cereals wheat and rye in a comparable way. • Potato yield dynamics were independent from long-term tillage effects. [ABSTRACT FROM AUTHOR]

The objective of this study was to determine how to establish high and stable yields of winter rye under the impact of highly varying seeding densities and delayed sowing date. A field trial with three winter rye cultivars (two population cultivars and one F1 hybrid) was conducted on a sandy site over a period of three years. The results showed that seeding density, cultivar choice, and annual weather conditions are important factors impacting the yield variability of winter rye. Higher seeding densities led to higher and slightly more stable yields of winter rye. Moreover, a cultivar-adapted seeding date seemed to exploit yield potential advantageously. Interestingly, all three cultivars showed better yield stability with a two-week delay in seeding date. This study suggests that cultivar choice and management practices such as modulation of seeding date and seeding density play an important role in improving the grain yield and yield stability of winter rye. [ABSTRACT FROM PUBLISHER]

The objective of this study was to examine the importance of farmers' variety choice in organic and conventional cereal production and to understand which particular crop varieties are required by farmers for climate change adaptation. A broad-based survey was conducted which included data from 119 organic and 305 conventional farmers in Germany. Most of the farmers surveyed recognized the existence of climatic changes and their negative impacts on cereal production. Given this context, the choice of climate-adapted varieties was very important to the majority of respondents. The farmers ranked eco-stability, grain yield performance and steadiness as the most crucial varietal requirements. For cereals, farmers perceived that a higher eco-stability was most important compared to other variety types. The selection of varieties with high and eco-stable yields levels should be given increased consideration, with their use likely to improve overall cereal yields and reduced plant production risks due to climate change. [ABSTRACT FROM AUTHOR]

The objective of this study was to understand what particular crop variety requirements farmers were demanding in the context of climate change adaptation. A broad-based survey was used to collect primary data from 515 farmers. The majority of farmers interviewed perceived climatic change impacts on crop production, with more than half stating that they would rely on a locally adapted variety selection. The respondents identified yield stability, yield performance, and drought tolerance as being particularly important variety properties. In selecting varieties, their own experience, exchanges with colleagues, and recommendations from the State Plant Varieties Offices were identified as being important sources of information. The research highlights a need to reflect farmers' demands in official variety recommendations such as plant breeding. This would help support the choice of varieties in agricultural practice and reduce crop production risks in regard to climate change risk. [ABSTRACT FROM AUTHOR]

The anticipated increases in environmental variability associated with climate change may lead to enhanced abiotic plant stresses (e.g., heat stress, drought stress, etc.) resulting in greater inter-annual yield fluctuations and higher crop production risk. While there has been increasing attention to adaptation measures, there is little evidence available on how to change agronomic management strategies to maintain stable yields in winter rye production systems in Poland. This study uses rye yields from the unique Skierniewice Long-term experiment (Poland) to examine for the first-time the long-term effects of different nutrient regimes on crop yield stability from 1966 to 2015. Yields from six combinations of mineral fertilizers and lime (CaNPK, NPK, CaPK, CaNK, CaNP, Ca), with and without additional manure, were used to estimate the temporal yield variability of winter rye. A novel statistical approach based on a mixed model approach with REML (restricted maximum likelihood) stability parameter estimation was used. The results showed that the use of additional manure in 'sub-optimal' mineral fertilizer treatments, such as Ca and CaPK (without mineral N), reduced the temporal yield variability of rye. In contrast, additional organic input led to more variable rye yields in already 'optimal' treatments including mineral N (CaNPK and NPK), compared to those with no additional manure. Winter rye given CaNPK and NPK, without additional organic manure demonstrated high yield and low temporal yield variability. In contrast, yields of treatments with no mineral N (Ca and CaPK) and no additional manure supply were low and unstable. In addition, it was found that increasing soil organic carbon resulted in larger, more stable yields. These findings highlight the importance of ensuring rye crops receive sufficient fertilizer to maintain crop production levels and yield stability, especially in dry years. They also demonstrate the importance of avoiding the excessive use of organic manures when fertilizer inputs are sufficient to meet crop demand. Overall, the study provides novel insights about how to maintain grain yields and minimize temporal yield variation of rye in arable cropping systems, which will become increasingly important in a changing climate in Poland and in other temperate climate areas. This study also highlights the importance of soil organic carbon for improving the climate resilience of winter rye, while simultaneously meeting the demand for more sustainable management of the soil. [ABSTRACT FROM AUTHOR]

• Higher crop diversity and organic matter inputs increased yield stability. • Moderate N fertilization (70 kg N ha−1) benefitted yield stability. • Organic matter improved environmental adaptability of barley in cereal rotations. • Production risk was lower with higher crop diversity and organic matter inputs. In the face of climate change, the potential impacts of adverse weather conditions on the productivity and vulnerability of cropping systems (CS) worldwide constitute a key agronomic issue upon which global food security depends. To date, little information regarding how the diversity of CS or agricultural practices affect the long-term yield responses of winter barley is available. The aim of this study was to investigate the impact of CS diversity in terms of cropping sequences, organic matter supplies, and nitrogen (N) fertilization on the yield vulnerability of winter barley. Yields were evaluated in terms of their stability, environmental adaptability, and production risk (probability of yield loss). Data from a 27-year experiment were statistically analyzed using three mixed models giving residual maximum likelihood estimates including the Shukla stability variance index, the Finlay-Wilkinson environmental regression, and the Eskridge risk assessment approach. The results showed that winter barley grown in cropping sequences dominated by cereals had lower yield stability and environmental adaptability and greater production risks compared with winter barley grown in CS with higher crop diversity and additional organic matter inputs. When barley yields were compared at three doses of mineral N, the highest yield stability was achieved with the medium N dose (70 kg N ha−1), followed by the higher level of N (140 kg N ha−1). The most unstable yields with the highest production risks were observed when barley was grown without any mineral N fertilization. Overall, a higher level of crop diversity with organic matter inputs and intermediate N fertilization resulted in lower yield vulnerability in winter barley. [ABSTRACT FROM AUTHOR]

In the face of a changing climate, yield stability is becoming increasingly important for farmers and breeders. Long-term field experiments (LTEs) generate data sets that allow the quantification of stability for different agronomic treatments. However, there are no commonly accepted guidelines for assessing yield stability in LTEs. The large diversity of options impedes comparability of results and reduces confidence in conclusions. Here, we review and provide guidance for the most commonly encountered methodological issues when analysing yield stability in LTEs. The major points we recommend and discuss in individual sections are the following: researchers should (1) make data quality and methodological approaches in the analysis of yield stability from LTEs as transparent as possible; (2) test for and deal with outliers; (3) investigate and include, if present, potentially confounding factors in the statistical model; (4) explore the need for detrending of yield data; (5) account for temporal autocorrelation if necessary; (6) make explicit choice for the stability measures and consider the correlation between some of the measures; (7) consider and account for dependence of stability measures on the mean yield; (8) explore temporal trends of stability; and (9) report standard errors and statistical inference of stability measures where possible. For these issues, we discuss the pros and cons of the various methodological approaches and provide solutions and examples for illustration. We conclude to make ample use of linking up data sets, and to publish data, so that different approaches can be compared by other authors and, finally, consider the impacts of the choice of methods on the results when interpreting results of yield stability analyses. Consistent use of the suggested guidelines and recommendations may provide a basis for robust analyses of yield stability in LTEs and to subsequently design stable cropping systems that are better adapted to a changing climate. [ABSTRACT FROM AUTHOR]