Context. The productivity of crops is influenced by the available net water balance, which relies on a complex interplay of edaphic and climatic factors. In this sense, rainfall is the leading water input for crop growth and yield, especially in water-scarce regions under semi-arid climates worldwide.

Aims. This study aimed to define the optimum cropping calendar and the agroclimatic and agroecological zones for rainfed maize in the state of Ceará, which is predominantly located within the Brazilian semi-arid region, assuming different rainfall scenarios.

Methods. We considered the subdivision of the study area into eight homogeneous precipitation regions according to the regional rainfall pattern. The climatic water balance for each region over two decades was calculated from historical weather data series, assuming three rainy scenarios: dry, regular, and rainy. The agroclimatic zoning was defined through the crop water balance results, soil classification, land use and occupation, slope and temperature, weighted through a multi-criteria decision analysis based on the Analytic Hierarchy Process.

Key results. The recommended planting period was broader in rainy conditions. However, there may be some dry spells between two 10-day intervals of the calendar, which impair plant growth depending on their intensity. For the dry scenario, the agroclimatic zoning showed that the marginal water deficiency covered 96.55% of the study area.

Conclusions. Rainfed maize cultivated under the semi-arid climate of Ceará state is viable in rainy conditions, partially restricted in regular years, and not recommended in dry years.

Implications. This study emphasises the importance of climate monitoring in effective planning for rainfed maize cultivation in semi-arid regions.

Context. Seasonal variations between the rain and dry seasons are the main obstacle to agricultural productivity in tropical regions, making it essential to conserve surplus for periods of scarcity. One of the limiting factors in ensiling grasses is moisture, requiring the use of additives or withering. Using a mixture of grasses and legumes can be an alternative to balance the advantages and disadvantages of both in the ensiling process, and mata-pasto hay (MPH) can be an option.

Aims. This study evaluated different forms of Tanzania grass (Megathyrsus maximum) and MPH silages, as well as silages with increasing levels of MPH.

Methods. Silages of Tanzania grass and MPH in their natural form, as well as silages with increasing doses of MPH, were evaluated for nutritional value, degradability in situ. The microbiology was also evaluated.

Key results. Among the types of silages, natural MPH and wilted MPH were superior to natural Tanzania grass silage. The use of MPH in Tanzania grass silages improves fermentation processes, the population of beneficial microorganisms, resulting in better nutritional value of these silages.

Conclusions. Natural and wilted MPH hay silages are qualitatively better compared to natural Tanzania grass silage. Increasing doses of MPH improve the quality of the silage. A recommended dose is 30% of MPH hay.

Implications. Adding MPH to silages is a way to reduce the negative impacts of this weed on pastures. However, further studies with the use of complementary additives are needed.

Context. Long-term multi-environment trials (METs) could improve genomic prediction models for plant breeding programs by better representing the target population of environments (TPE). However, METs are generally highly unbalanced because genotypes are routinely dropped from trials after a few years. Furthermore, in the presence of genotype × environment interaction (GEI), selection of the environments to include in a prediction set becomes critical to represent specific TPEs.

Aims. The goals of this study were to compare strategies for modelling GEI in genomic prediction, using large METs from oat (Avena sativa L.) breeding programs in the Midwest United States, and to develop a variety decision tool for farmers and plant breeders.

Methods. The performance of genotypes in TPEs was predicted by using different strategies for handling GEI in genomic prediction models including systematic and/or random GEI components. These strategies were also used to build the variety decision tool for farmers.

Key results. Genomic prediction for unknown genotypes, locations and years within TPEs had moderate to high predictive ability, accuracy and reliability. Modelling GEI was beneficial in small, but not in large, mega-environments. The latest 3 years were highly predictive of performance in an upcoming year for most years but not for years with unusual weather patterns. High predictive ability, accuracy and reliability were obtained when large datasets were used in TPEs.

Conclusions. Deployment of historical datasets can be accomplished through meaningful delineation and prediction for TPEs.

Implications. We have shown the performance of a simple modelling strategy for handling prediction for TPEs when deploying large historical datasets.

Context. The spike is a crucial organ for intercepting exogenous zinc (Zn) at the late growth stage of wheat (Triticum aestivum L.). However, the role of spikes in wheat biofortification has drawn little attention, and knowledge gaps exist with respect to absorption and translocation of exogenous Zn by wheat.

Aims. This study aims to determine the role of spikes in wheat biofortification when Zn is applied to the canopy, and to characterise the absorption and translocation of Zn applied to different wheat organs.

Methods. In two field experiments and one pot experiment, Zn was applied at different stages (heading or early filling stage) to the canopy or to different organs (flag leaf or spike), and Zn concentrations in various organs were determined. Zn interception, Zn absorption, recovery in grain, and translocation amount and rate were calculated.

Key results. With application to the canopy, the Zn interception rate of spikes was 13% at heading and 28% at early filling. Grain Zn concentration was improved by 17–33% under flag leaf Zn application and 30–37% under spike Zn application, with absorption accounting for 68–90% and 88–99% of Zn applied, respectively. Zn applied at heading was translocated throughout plants before anthesis, and then to spikes. Zn applied at early filling was entirely translocated to spikes. The amount of Zn translocated after flag leaf application and spike application accounted for 16–40% and 13–14% of absorbed Zn, respectively.

Conclusions. Spikes are critical for intercepting and absorbing exogenous Zn. The Zn absorbed by the spike was more effective for grain Zn biofortification than the Zn absorbed by the flag leaf.

Implications. The information generated from this study assists in understanding how wheat plants intercept, absorb and translocate Zn.

Context. Reliable seed production is a key requirement for successful year-on-year regeneration of annual pasture legumes.

Aims. The study aims were to investigate the developmental patterns of flowers and pods and the effect on seed number among cultivars of French (Ornithopus sativus Brot.) and yellow serradella (O. compressus L.); and to assess the effects of early flower loss.

Methods. Four cultivars of each species were grown in a glasshouse under non-limiting growth conditions. Date of flowering and numbers of flowers, pods and seeds were assessed for up to 20 reproductive nodes on two stem axes per plant (n = 5 plants). A flower removal treatment was imposed to assess whether early flower loss affected flower and/or pod production.

Key results. Flowering in the serradellas was indeterminate, but for all cultivars there was a peak period of flower and pod production, with the timing and duration of the peak period differing among cultivars. Peak flowering occurred primarily because the proportion of plants flowering began to decline, but the number of flowers per reproductive node and the number of pods formed per node also declined with time. Compensation for early flower loss was observed for most cultivars because of a longer duration of pod formation and/or greater numbers of pods developed on higher reproductive nodes.

Conclusions. This study demonstrated that there is diversity in the patterns of flowering and podding and number of seeds initiated among serradellas.

Implications. Diversity in flowering and podding patterns combined with a capacity to compensate for early flower loss may be used to develop serradellas better able to cope with environmental stressors (frost, drought, heat) experienced during the flowering window.

Context. A challenge for the livestock sector is to improve the production and nutritive value of forage grasses through sustainable management strategies.

Aims. This study evaluated the impact of management on the productive and nutritive value of five pasture-based production systems: irrigated pasture with 600 kg nitrogen (N) ha⁻¹ (IP600); rainfed pasture with 400 kg N ha⁻¹ (RP400); rainfed pasture with 200 kg N ha⁻¹ (RP200); silvopastoral with 200 kg N ha⁻¹ (SP200); and degraded pasture without N fertilisation (DP0).

Methods. During two experimental years, samples were collected pre- and post-grazing to determine forage and nutritional parameters. Land-saving effects and efficiencies of N fertilisation and water use were calculated.

Key results. For C₄ grasses, forage mass accumulation was greater for IP600 and RP400. IP600 also presented the greatest leaf area index and crude protein concentration, whereas DP0 presented the lowest values of both. For C₃ grasses in the IP600 treatment, greater forage mass accumulation and leaf area index were found in winter than in autumn; all nutritional characteristics were not affected by season of the year. For land-saving effect, and N- and water-use efficiencies, IP600, RP400 and RP200 presented higher values than DP0 and SP200.

Conclusions. More intensified systems with proper management allowed better productive and nutritional characteristics than degraded pasture or silvopasture, especially during seasons with greater precipitation or when irrigated.

Implications. Intensification practices make better use of natural resources (water and land) and agricultural inputs (N fertiliser) to ameliorate the effects of seasonality and improve quality and productivity of tropical grasses in pasture-based livestock production systems.