This study analyses the impact of higher night temperature during the tillering phase on grain yield, focusing on crop development and tiller production dynamics in wheat (Triticum aestivum L.). Field experiments were carried out at the School of Agriculture, Buenos Aires, Argentina during the 2015 and 2016 growing seasons and combined: (1) two nitrogen availability levels (60 and 200 kg N ha^–1) and (2) two night temperature conditions (control unheated and night temperature increase (NTI) during the tillering phase). The heating treatment increased night temperature ∼2.3°C above the ambient night temperature. Across growing seasons, average minimum temperature during the tillering phase ranged from 8.5°C to 12.4°C. Warmer nights reduced time to anthesis (∼4 days) due to a shortening in the duration of the tillering phase. NTI did not modify the maximum tiller number at plant level or per unit area. Higher N availabilities increased maximum tiller number ∼30% compared with low N levels. Increased night temperature did not modify (P = 0.3418) grain yield in high and low N availabilities. Although development during the tillering phase was accelerated, the NTI during this stage would have a minor impact on both tillering and yield and its numerical components.

Water shortage and drought stress in the reproductive stage of wheat (Triticum aestivum L.) considerably affect grain yield (GY). Mapping genes for drought tolerance assists in selection for drought improvement. In the present study, we evaluated breeding values based on best linear unbiased predictions (BLUPs) and drought tolerance/susceptibility indices (DT/SIs), and identified marker–phenotype associations in 220 doubled haploid (DH) lines. The DH lines were evaluated for GY and 1000-grain weight (TGW) under drought stress and well-watered conditions at the heading stage in 2015 and 2016. The linkage map comprised 1333 SSR, DArT and SNP markers with an average density of 2.18 markers per cM. The BLUPs were significantly correlated with GY of the lines. Significant correlations were found between stress tolerance score (STS) and drought response index, yield index, yield stability index, geometric mean productivity and stress tolerance index. The lines DH_R295 and DH_R360 had the highest breeding values for GY and STS. Major QTLs, one main effect and eight epistatic, were identified for the DT/SIs. A major QTL was identified for STS-GY, which explained 11.39% of the STS-GY variation in 2015. This QTL was co-located with QTLs for yield index-GY and yield stability index-GY within the BS00066932_51–gwm0314b marker interval (48 cM on 3B). The search for gene annotation showed that BS00066932_51 overlapped with protein-encoding genes. In conclusion, the QTL-linked markers help genotype selection for the improvement of drought tolerance, and they are good candidates for use in genomic selection.

This study investigated the impact of soil compaction owing to cotton picker traffic, and the impact of this compaction on cotton yield on a row-by-row basis across the field under both random traffic farming (RTF) and controlled traffic farming (CTF) systems. Measurements of soil water content, dry bulk density and soil penetration resistance were taken and compared with a depth of 80 cm both before and after traffic. It was found that the traffic of JD7760 round-bale cotton picker caused significant compaction in cotton rows and furrows located between, adjacent to, and in wheel tracks under both RTF and CTF systems, particularly for the top 30-cm depth. Because of the soil compaction, the yield was more significantly reduced (7∼10% by the machine-pick method) in the rows between the dual-wheel than in those adjacent to the wheel track. Adopting CTF reduces the area of soil compaction and ensures the maintenance of soil characteristics of the cultivated portions of the farm, hence enhancing cotton yield.

Reducing input of chemical fertiliser to cotton fields has the benefits of reduced costs, increased crop production efficiency, and positive environmental impact. We investigated the impacts of stalk management and fertiliser application on the morphology, physiological activity and nutrient use efficiency of cotton roots in arid areas when grown under drip irrigation with plastic film mulching. This 9-year field experiment involved a split-plot design with two stalk management treatments (removed or mixed with soil) as main plots and four fertiliser treatments (no fertiliser, NPK fertiliser, poultry manure, combined NPK fertiliser plus poultry manure) as subplots. Fertilisation increased root tissue mass density, specific surface area, triphenyl tetrazolium chloride reducing capacity, and glutamine synthetase, but decreased specific root length. Straw return and fertilisation increased soil available N, P and K. Nutrient use efficiencies of N, P and K in roots were sensitive to fertilisation treatment, whereas nutrient use efficiencies in total dry matter were sensitive to straw return treatment. Fertilisation increased the root:shoot ratio, root biomass, fine:coarse root mass ratio, and seed cotton yield. Combined application of NPK fertiliser and poultry manure can prompt the formation of fine roots, which maximised the contact area between poultry manure and roots, thus increasing the chance of the root acquiring mineral nutrients. Therefore, organic matter promotes the absorption of mineral nutrients by roots, thereby improving the efficiency of fertiliser utilisation.

Salinity and drought are major abiotic stresses limiting plant growth and crop productivity. To evaluate the comparative effects of salt and drought stress on castor bean (Ricinus communis L.) germination and early seedling growth, a germination experiment and a seedling experiment were conducted to determine the responses of castor bean (cvs Zibi 5 and Zibi 9) to polyethylene glycol (PEG-6000) and sodium chloride (NaCl) with a range of gradient water potential levels, including 0 (control), –0.13 MPa, –0.2 MPa and –0.6 MPa. Results showed that both stresses caused by NaCl and PEG-6000 decreased germination percentage (GP), germination index (GI), fresh weight (FW), leaf gas exchange parameters (Pn, Ci and Tr) and chlorophyll pigments (Chl a and Chl b). The PEG-treated plants suffered higher restrictions in seed germination and seedlings growth than the NaCl-treated plants. Moreover, the PEG treatments caused more significant reductions in GP, Chl a, FW and Tr, as compared with NaCl treatment. On average, the GP under PEG stress was decreased by 22.3% and 22.0% for Zibi 5 and Zibi 9, respectively, in comparison to NaCl stress. Our study showed that both salt and water stress caused similar reductions in germination percentage, biomass accumulation, leaf gas exchange and chlorophyll pigments, while severer detrimental effects were induced by water stress as compared with salt stress.

This study investigated whether geostatistical methods can be applied to severely drought-affected pastures to assess spatial variability in sward height (SH) and dry matter yield (DMY) and change in SH and DM in response to grazing. Geo-referenced SH data were collected using a rapid, non-destructive method (rapid pasture meter) and analysed by geostatistical methodology. Eight severely drought-affected paddocks (∼1.25 ha) were grazed individually by two groups of 20 Angus heifers in two 28-day phases (P1 and P2) between 2 July and 29 August 2019. Pasture DMY was estimated from calibration equations developed for P1 and P2. Ordinary kriging was used to generate estimated surface forming maps with which to visualise the spatial variability. The degree of spatial dependence (dSD) was strongest for SH during P2 post-grazing (11%) and for DMY during P2 pre-grazing (6%). For change in SH, the dSD was 50% for P1 and 0% for P2. Disappearance of DMY dSD was 56% for P1 and 47% for P2. The range of spatial dependence (distance until variability stabilised) for both SH and DMY was lowest for P1 post-grazing (11 m), indicating that intensive sampling is required. The ranges of spatial dependence for the change in both SH and DMY were similar for P1 and P2. These results confirm that intensity of grazing by cattle is not random. Incorporation of this methodology into rapid, non-destructive pasture data collection devices would assist producers and their advisers in improving grazing management decisions. Further analysis with data from non-drought affected pastures is required to determine the robustness of this method.

Information on the nature and amount of genotype × environment (GE) interaction for economic traits and persistence is extremely rare in smooth bromegrass (Bromus inermis Leyss.), especially under drought stress. In this study, 25 half-sib (HS) families of smooth bromegrass were evaluated in the field during five consecutive years under normal and water deficit conditions. The effect of water deficit on dry forage yield was increased from the first year to the fifth, and manifested as a decline in persistence of HS families. Based on narrow-sense heritability estimates, additive gene action was found to be an effective factor in the control of yield components, whereas forage yield is controlled by both additive and non-additive gene actions. Considering the three parameters of stability of combining ability, mean performance and drought tolerance simultaneously, it was inferred that four parental genotypes were superior and stable with high values of general combining ability. This indicates that when developing synthetic varieties from these genotypes, both stability and plant productivity are transmitted to their progenies.