Crop rotational diversity can mitigate climate-induced grain yield losses.

Diversified crop rotations have been suggested to reduce grain yield losses from the adverse climatic conditions increasingly common under climate change. Nevertheless, the potential for climate change adaptation of different crop rotational diversity (CRD) remains undetermined. We quantified how climatic conditions affect small grain and maize yields under different CRDs in 32 long-term (10-63 years) field experiments across Europe and North America. Species-diverse and functionally rich rotations more than compensated yield losses from anomalous warm conditions, long and warm dry spells, as well as from anomalous wet (for small grains) or dry (for maize) conditions. Adding a single functional group or crop species to monocultures counteracted yield losses from substantial changes in climatic conditions. The benefits of a further increase in CRD are comparable with those of improved climatic conditions. For instance, the maize yield benefits of adding three crop species to monocultures under detrimental climatic conditions exceeded the average yield of monocultures by up to 553 kg/ha under non-detrimental climatic conditions. Increased crop functional richness improved yields under high temperature, irrespective of precipitation. Conversely, yield benefits peaked at between two and four crop species in the rotation, depending on climatic conditions and crop, and declined at higher species diversity. Thus, crop species diversity could be adjusted to maximize yield benefits. Diversifying rotations with functionally distinct crops is an adaptation of cropping systems to global warming and changes in precipitation.

Effects of soil compaction on grain yield of wheat depend on weather conditions.

The use of heavy farm machinery has resulted in widespread soil compaction in many regions of the world. Compacted soil limits the access of crops to soil water and nutrients and is expected to reduce crop productivity, but the influence of weather conditions on the interactions between compacted soil and crop productivity is unclear. Furthermore, early vigor has been regarded as a promising trait for improving the yield of crops grown under edaphic stress such as soil compaction. We aimed to assess the combined effects of soil compaction and contrasting weather conditions on growth and grain yield of spring wheat, and to evaluate the association between early vigor and grain yield under temporal variations of the soil physical conditions. Nine spring wheat genotypes were grown on compacted and non-compacted soils during two cropping seasons with contrasting weather conditions in Central Sweden. Compared to the non-compacted treatment, soil compaction increased the relative growth rate of shoot biomass from sowing to stem elongation, and from stem elongation to flowering in the drier year (2018), but decreased the same traits in the wetter year (2019). The contrasting effects of soil compaction on shoot growth in the two years could be explained by soil moisture and penetration resistance associated with the interactive effects of soil compaction and weather condition. Higher early vigor, here indicated by higher relative growth rate from sowing to stem elongation, was associated with reduced grain yield under the progressively drying and hardening soil conditions during the entire cropping season of both years. We conclude that the interactive effects of soil physical and weather conditions need to be considered when evaluating the impact of soil compaction on crop growth and productivity. The potential of early vigor to increase grain yield is strongly influenced by the temporal dynamics of soil physical conditions.

Evidence for magnesium-phosphorus synergism and co-limitation of grain yield in wheat agriculture.

Modern crop production is characterized by high nitrogen (N) application rates, which can influence the co-limitation of harvested yield by other nutrients. Using a multidimensional niche volume concept and scaling exponents frequently applied in plant ecological research, we report that increased N and phosphorus (P) uptake in a growing wheat crop along with enhanced grain biomass is associated with more than proportional increase of other nutrients. Furthermore, N conversion efficiency and grain yield are strongly affected by the magnesium (Mg) to P ratio in the growing crop. We analyzed a field trial in Central Sweden including nine wheat varieties grown during two years with contrasting weather, and found evidence for Mg co-limitation at lower grain yields and P co-limitation at higher yields. We argue that critical concentrations of single nutrients, which are often applied in agronomy, should be replaced by nutrient ratios. In addition, links between plant P and Mg contents and root traits were found; high root number enhanced the P:N ratio, whilst steep root angle, indicating deep roots, increased the Mg:N ratio. The results have significant implications on the management and breeding targets of agriculturally grown wheat, which is one of the most important food crops worldwide.

Shoot and Root Traits Underlying Genotypic Variation in Early Vigor and Nutrient Accumulation in Spring Wheat Grown in High-Latitude Light Conditions.

Plants with improved nutrient use efficiency are needed to maintain and enhance future crop plant production. The aim of this study was to explore candidate traits for pre-breeding to improve nutrient accumulation and early vigor of spring wheat grown at high latitudes. We quantified shoot and root traits together with nutrient accumulation in nine contrasting spring wheat genotypes grown in rhizoboxes for 20 days in a greenhouse. Whole-plant relative growth rate was here correlated with leaf area productivity and plant nitrogen productivity, but not leaf area ratio. Furthermore, the total leaf area was correlated with the accumulation of six macronutrients, and could be suggested as a candidate trait for the pre-breeding towards improved nutrient accumulation and early vigor in wheat to be grown in high-latitude environments. Depending on the nutrient of interest, different root system traits were identified as relevant for their accumulation. Accumulation of nitrogen, potassium, sulfur and calcium was correlated with lateral root length, whilst accumulation of phosphorus and magnesium was correlated with main root length. Therefore, special attention needs to be paid to specific root system traits in the breeding of wheat towards improved nutrient accumulation to counteract the suboptimal uptake of some nutrient elements.