Above-ground Dry Matter Accumulation Research Articles

Winter wheat source‐sink relationships under various planting modes, complementary irrigation, and planting densities

AbstractVarious agronomic practices can affect the processes of aboveground dry matter accumulation (source) and grain filling (sink), resulting in yield differences. Improved source‐sink relationships can facilitate the production and accumulation of assimilates to increase the productivity of winter wheat (Triticum aestivum L.). A two‐season field experiment was undertaken on winter wheat during 2020–2021 and 2021–2022. In a split‐split‐plot design with three replicates (randomized blocks), we compared two planting modes (ridge‐furrow planting with plastic mulching [RFPM]; traditional flat planting [TF]), two complementary irrigation levels (I30+30: 30+30 mm; I0: no irrigation), and three planting densities (D1, D2, and D3: 240, 360, and 480 plants m−2). The results showed that RFPMI30+30 significantly increased maximum yield by 28.5% compared with TFI0. Although D3 increased the number of effective spikes per unit area and duration of grain filling compared to D2, it reduced the number of grains per spike, 1000‐grain weight, and average filling rate. Compared to TF and I0, RFPM and I30+30 improved the sink/source ratio by 5.3% and 6.5%, respectively. Grain yield peaked at D2 in the RFPM and at D3 in the TF. Medium planting density (D2) and complementary irrigation (I30+30) during the wintering and reviving periods under RFPM can achieve better source‐sink balance relationships and the maximum grain yield of winter wheat. Overall, we believe that in most cases, wheat yields are source‐limited and can be improved by ridge‐furrow planting with plastic mulching, complementary irrigation, and planting density regulation.

A new perennial forage module coupled with the ECOSMOS terrestrial ecosystem model: Calibration and evaluation for Urochloa (syn. Brachiaria) brizantha

Pastures represent the main land use type in Brazil and are used for livestock production and maintenance of land ownership. Most pasture areas exhibit signs of degradation related to inadequate management, which affects pasture biomass production. Terrestrial ecosystem models are effective tools for evaluating the economic and ecological returns associated with distinct management scenarios. In this paper, a new forage module implemented in the ECOSystem MOdel Simulator (ECOSMOS) is formulated, and ECOSMOS-Forage model calibration and evaluation results were obtained for estimating tropical forage growth under continuous and rotational stocking methods subject to grazing or cutting regimes. A set of equations to simulate the daily carbon allocation, growth, senescence, and morphological characteristics of Urochloa (syn. Brachiaria) brizantha cvs. Marandu and Piatã were proposed. Biophysical and physiological parameters, including the solar radiation balance, soil water content, evapotranspiration and carbon assimilation, were calibrated and evaluated with one micrometeorological experiment. Additionally, two sets of parameters were calibrated for Marandu grass growth under continuous and rotational stocking. Based on the Marandu parameterization, a third set of parameters, thereby adjusting a few parameters, was derived for the Piatã grass under rotational stocking. The ECOSMOS-Forage model could successfully capture the energy, carbon and water fluxes and biomass dynamics during growth cycles. The net radiation, evapotranspiration and gross primary production were simulated with agreement index (d) values of 0.97, 0.89, and 0.95, respectively, during the calibration phase and 0.98, 0.90, and 0.93, respectively, during the evaluation phase. Regarding model application to simulate forage growth under rotational stocking, the model could estimate aboveground, leaf and stem dry matter accumulation levels with d values ranging from 0.91 to 0.98. Although forage growth is relatively difficult to simulate, compared with annual crops, the results suggested that the model could provide high potential for simulating tropical perennial forage grasses.

More N fertilizer, more maize, and less alfalfa: maize benefits from its higher N uptake per unit root length.

Root plasticity is fundamental to soil nutrient acquisition and maximizing production. Different soil nitrogen (N) levels affect root development, aboveground dry matter accumulation, and N uptake. This phenotypic plasticity is well documented for single plants and specific monocultures but is much less understood in intercrops in which species compete for the available nutrients. Consequently, the study tested whether the plasticity of plant roots, biomass and N accumulation under different N levels in maize/alfalfa intercropping systems differs quantitatively. Maize and alfalfa were intercropped for two consecutive years in large soil-filled rhizoboxes and fertilized with 6 different levels of N fertilizer (0, 75, 150, 225, 270, and 300 kg ha-1). Root length, root surface area, specific root length, N uptake and yield were all increased in maize with increasing fertilizer level, whereas higher N rates were supraoptimal. Alfalfa had an optimal N rate of 75-150 kg ha-1, likely because the competition from maize became more severe at higher rates. Maize responded more strongly to the fertilizer treatment in the second year when the alfalfa biomass was much larger. N fertilization contributes more to maize than alfalfa growth via root plasticity responses. Our results suggest that farmers can maximize intercropping yield and economic return by optimizing N fertilizer management.

Enhancing maize yield through understanding the novel shoot-root interaction in morphology among hybrids with dense planting

ContextUnderstanding the shoot-root characteristics and their interaction of maize is essential to break the constraints of the densification process and improve grain yield. ObjectiveThe objective of the work was to study the interaction between the above-ground canopy and below-ground root system in morphology and its relationship to grain yield in dense planting with different hybrids. MethodsThis study conducted a 2-yr field experiment with three modern hybrids (JNK728, ZD958 and XY335) at the Wuqiao Experimental Station in Northern China. ResultsAmong hybrids, XY335 attained the highest grain yield of 14,886.9 kg hm−2 in 2019 and 10,078.8 kg hm−2 in 2020 with a density of 7.5 × 104 plants hm−2. For the shoot at the silking stage (R1), the lowest leaf orientation value for both middle and upper leaves and ear-to-height ratio among three hybrids were found in XY335 with the compact plant phenotype. Meanwhile, the highest photosynthesis rate of ear leaves (33.0 umol m2˙s−1) at R1 was also observed in XY335. At physiological maturity (R6), the above-ground dry matter (AGDM) was 4.6%− 10.4% higher in XY335 than the other two hybrids. For the root system at both R1 and R6 with the density of 7.5 × 104 plants hm−2, the highest value for root system indicators in morphology such as root total length (RL), root surface area (RSA), root volume (RV) was observed in XY335. From R1 to R6, RL, RSA and RV in XY335 averaged 24,749.6 cm, 3486.8 cm2, 51.5 cm3, 1.3–14.6% higher than JNK728, and 10.2–23.9% higher than ZD958, respectively. Furthermore, the lower senescence of the root system was also observed in XY335, with a 22.0–32.1% lower decrease from R1 to R6 in RL, RSA, and RV compared with the other two hybrids. ConclusionsFor the shoot-root interaction, per unit decrease in morphology indicator in the root per plant with density increase of XY335 accompanied with more AGDM accumulation and thus higher grain yield. ImplicationsThe observations on shoot-root characteristics and their interaction from this study are essential to selecting a hybrid that allows a better adaptation to planting at high density, developing an effective management strategy, and breeding high-density tolerant hybrids.

Effects of Zeolite on Physiological Characteristics and Grain Quality in Rice under Alternate Wetting and Drying Irrigation

Background: Zeolite (Z) is gradually used in rice production due to its holding ability for water and nutrients, but limited information is available on how its physiological function affects rice grain yield and quality under water stress. Methods: This study aimed to investigate the effect of Z application on rice physiological characteristics, dry matter and nitrogen accumulation, grain yield and quality under continuous flooding (CF) and alternate wetting and drying irrigation (AWD). Results: The results showed that, compared with CF, AWD reduced leaf SPAD, root bleeding intensity, aboveground dry matter and nitrogen accumulation, resulted in lower grain yield without Z application, but improved root–shoot ratio and root N accumulation. Z application increased dry matter and N accumulation, and subsequent grain yield by improving leaf SPAD and root bleeding intensity. Both AWD and Z application improved water use efficiency. AWD reduced head rice rate, chalky rice rate and chalkiness, but improved the taste value by increasing the breakdown and reducing the setback. Z application improved protein content, reduced breakdown and setback, but increased chalky rice rate and chalkiness. Conclusions: These results indicated that AWD and Z application could achieve several benefits including improved grain yield, grain quality and water use efficiency.

Effect of Nitrogen Management on Wheat Yield, Water and Nitrogen Utilization, and Economic Benefits under Ridge-Furrow Cropping System with Supplementary Irrigation

Supplemental irrigation under a ridge-furrow (RF) cropping system is a valuable cropping practice that balances resource efficiency and high crop yield. However, the effects of nitrogen management on crop growth, yield formation, and economic benefits under RF systems have not been clearly investigated. In this study, the experiment was designed with three experimental factorials, including three cropping systems (RF, RF cropping with 80 mm irrigation; TF1, traditional flat cropping with 200 mm irrigation; and TF2, traditional flat cropping with 80 mm irrigation), two nitrogen application rates (NL, 180 kg N ha−1; NH, 240 kg N ha−1), and two fertilizer application models (B, all nitrogen fertilizers were applied basally at the pre-sowing stage; BT, nitrogen fertilizer was applied at both the pre-sowing and jointing stages at a ratio of 1:1). A two-year field experiment was conducted to investigate the effects of nitrogen fertilizer management on wheat yield, water and nitrogen utilization, and economic benefits under the RF cropping system. The results showed that the RF system significantly increased the soil moisture content and improved the water productivity (WP) and grain yield of wheat. Nitrogen reduction (NL) under the RF system did not affect the water use of the wheat compared with traditional high nitrogen application (NH) but increased the nitrogen uptake and fertilizer productivity of the wheat. Although NL led to a reduction in aboveground dry matter accumulation, it did not significantly affect the yield of wheat but increased the net income of wheat cultivation. Under NL conditions, the BT nitrogen application model promoted nitrogen uptake in wheat and ameliorated the reduction in grain protein content due to plastic film mulching, and this model is an integrated planting practice that trades off wheat yield and quality. These findings suggest that NLBT is a promising and recommendable cropping practice under RF systems considering resource utilization, high yield and quality, and economic efficiency.

Effects of Nitrogen Application Level on Growth and Yield Of Winter Wheat

In order to achieve higher crop yield and improve the utilization efficiency of nitrogen fertilizer resources. Effect of nitrogen on the tillering ability, the aboveground dry matter mass and yield of winter wheat (WW) during the growing period were analyzed in a field experimental plot of Qinling Field Monitoring Center Station in Baoji City, Shaanxi Province from 2020 to 2021. Results demonstrated that nitrogen use significantly improved the tillering ability of WW during the overwintering and turning green stage; however, the use of nitrogen > 120 kg/hm2 did not have a significant impact on the tillering ability of WW. The growth stages were directly proportional to the extent of aboveground dry matter accumulation (DMA) of WW and were found to be maximum at maturity. Greater usage of nitrogen significantly enhanced aboveground DMA before the jointing stage, but nitrogen application as high as 270 kg/hm2 was not conducive to the aboveground DMA after the jointing stage. For WW, at first, the yield increased and then decreased with the increased concentration of nitrogen. When the nitrogen application level was 120 kg/hm2, the highest yield of WW was 7506 kg/ha. However, there was an insignificant increase in yield at nitrogen levels > 120 kg/hm2. In the study area, at nitrogen > 195 kg/hm2, a decrease in yield was observed. Therefore, the recommended nitrogen application level in this area was 120kg/hm2. Bangladesh J. Bot. 51(4): 937-941, 2022 (December) Special

Effects of Previous Fall–Winter Crop on Spring–Summer Soybean Nutrition and Seed Yield under No-Till System

Interest in fall–winter species options for rotation with soybean (Glycine max (L.) Merr.) has arisen; however, little is known about how they can affect the performance of subsequent soybean under a no-tillage system in tropical environments. Our objective was to evaluate the leaf nutrient concentration, aboveground dry matter (DM) accumulation, macronutrient uptake, yield components, and seed yield of soybean cropped in succession to different crop species. Consequently, a field experiment was conducted during three consecutive growing seasons in Botucatu, São Paulo State, southeastern Brazil. The experiment was arranged in a randomized complete block design with four replicates. The treatments consisted of the cultivation of five crops (crambe (Crambe abyssinica Hochst. ex. R.E. Fries), maize (Zea mays L.), safflower (Carthamus tinctorius L.), sorghum (Sorghum bicolor (L.) Moench), and sunflower (Helianthus annuus L.)) in rotation with soybean, in addition to plots that lie fallow (spontaneous weeds) in the soybean off-season, totaling six treatments. Letting plots lie fallow during the off-season reduced the DM accumulation, nutrient uptake, and seed yield of the soybean crop in succession. Preceding cultivation of fall–winter crambe or sunflower favored the uptake of P, K, Ca, Mg, and S by the following soybean crop. The cultivation of sorghum, safflower, and crambe as fall–winter crops also increased the seed yield of subsequent soybean (from 12 to 18% on the average of three growing seasons) compared to fallow plots. The highest increases in soybean seed yield were found in succession to maize (37%) or sunflower (45%) in the second and third growing seasons, respectively.

Effects of Different Levels of Nitrogen Supply on Key Enzyme Activities of Nitrogen Metabolism and Growth Stimulation of Endive (Cichorium endivia L.)

In recent decades, people have blindly pursued increased yield; the excessive use of fertilizer not only causes the widespread waste of resources but also puts great pressure on environmental protection. In this study, to find out the optimum nitrogen application to endive crops under hydroponic conditions, this experiment was conducted to investigate the changes in nitrate reductase (NR), nitrite reductase (NiR), glutamine synthetase (GS), and glutamate dehydrogenase (GDH) activities under different nitrogen supply levels, and to fit the equations between nitrogen supply levels and aboveground dry matter accumulation, the aboveground nitrogen accumulation, and the yield of endive crops. The results showed that the activities of the key enzymes of nitrogen metabolism were higher at nitrogen supply concentrations of 8 and 11 mmol·L−1. The dry matter and nitrogen accumulation of endive at different nitrogen supply levels were analyzed with the logistic model; the theoretical yield was found to be the highest at 9.935~11.448 mmol·L−1 of nitrogen application in the two different fertility trials by function fitting.

Impact of Sowing Time and Genotype on Water Use Efficiency of Lentil (Lens culinaris Medick.)

Productive water use can be an effective adaptation strategy for improving crop performance. A 2-year field study was undertaken in 2018 and 2019 to investigate the effect of sowing date and genotype on water-use efficiency of lentils grown in diverse locations in Australia. Above-ground dry matter accumulation, grain yield, soil evaporation, water use, and water-use efficiency (WUE) were measured and/or calculated at crop maturity. Early sowing (SD1/mid-April), late maturity and supplementary irrigation increased water use. The long growth cycle resulting from early sowing influenced WUE for dry matter production and grain yield. WUE ranged from 10.5 to 18.8 kg dry matter ha−1 mm−1 (WUEET (evapotranspiration)) and 17.1 to 28.3 kg dry matter ha−1 mm−1 (WUET (transpiration)) for dry matter production. For grain yield, WUE ranged from 2.11 to 5.65 kg grain ha−1 mm−1 (WUEET) and 4.71 to 9.19 kg grain ha−1 mm−1 (WUET). There was more water loss through soil evaporation in SD1 compared to the other sowing dates. Excessive or limited availability of water did not translate to more dry matter accumulation and grain yield. The study concluded that SD1 gives the maximum water productivity for biomass, and SD2 (end of April) and SD3 (mid-May) for grain yield.

Optimizing plastic mulching improves the growth and increases grain yield and water use efficiency of spring maize in dryland of the Loess Plateau in China

Transparent plastic film mulching (PFM) with flat cropping cultivation has been widely applied to grow maize (Zea mays L.) in dryland agricultural production areas of the Loess Plateau in China. However, with global warming-induced gradual increase in soil temperature, film-mulched spring maize experiences premature senescence and yield loss. In this study, a new form of mulching strategy involving dual mulching of transparent plastic film with whole maize stalks in a flat plot was established to improve growth and increase water use efficiency (WUE), precipitation use efficiency (PUE), and spring maize yield. The field experiment was conducted in 20 182 019, and 2020 on a conventional flat plot without mulching (CK), a flat plot with single transparent PFM, and a flat plot of transparent film mulching with whole maize stalks (PFM+ST) in the dryland of the Loess Plateau in China, to quantify the effects of different treatments on soil hydrothermal conditions, maize phenology, plant growth dynamics, WUE, PUE, and maize yield. Results demonstrated that soil water storage (SWS) at 0–100 cm soil layer in PFM and PFM+ST were significantly superior to those in CK, but SWS did not significantly differ between PFM and PFM+ST. Soil temperature under PFM+ST at 0–25 cm soil layer decreased by 1.2 ℃ compared with that under PFM during growth, especially in early growing seasons (20–60 days after sowing [DAS]). PFM+ST extended vegetative and reproductive growth periods by 1–2 and 6–7 days compared with those in PFM, respectively. In later growth period (80–120 DAS), PFM+ST increased the root dry matter weight, SPAD, and LAI and significantly increased the aboveground dry matter accumulation. PFM+ST significantly increased the 100-kernel dry weight, grain yield, WUE, and PUE. PFM+ST had 3-year average grain yields of 10.82% and 36.48% greater than PFM and CK, respectively. The corresponding WUE and in 0–200 cm soil layer improved by 12.55% and 39.84%, and PUE improved by 10.82% and 36.48%, respectively. With global warming, applying PFM+ST cultivation practice effectively extended growth period and increased mulching spring maize yield and WUE in the study site.

Weed Competition Effects on Growth and Yield of Spring-Sown White Lupine

White lupine (Lupinus albus L.) is an annual legume that is grown for both seeds and green biomass, but several agronomic aspects of this crop, including response to weed competition, have not been studied extensively. Field experiments over two growing seasons (2012 and 2016) were carried out in Orestiada, Greece, to study the growth and development of spring-sown white lupine under season-long weed competition from natural weed flora compared with its growth without weed competition. Treatments were arranged in a randomized complete block design with four replications and included (i) a non-treated (weedy) control, where weeds (Chenopodium album and Sorghum halepense) remained in the plots throughout the experiments and (ii) a weed-free control, where weeds were removed upon crop emergence and the plots were kept free of weeds throughout the experiments by hand removal. The presence of Chenopodium album and Sorghum halepense reduced the aboveground dry matter accumulation of white lupine ‘Multitalia’ at 7 weeks after crop emergence by 18.0% in the first growing season and 29.5% in the second growing season, while the corresponding decrease in the aboveground dry matter accumulation at 9 weeks after crop emergence was 25.3 and 33.4%. However, the reduction in dry matter accumulation was limited to lower levels after flowering (9.9% in the first and 12.8% in the second growing season). In both growing seasons, values of the ability to withstand competition (AWC) index were lower at 7 and 9 weeks from crop emergence than at maturity. Seed yields were 1.58 Mg per ha under weedy conditions and 2.20 Mg per ha under weed free conditions in the first growing season, and 1.59 and 2.32 Mg per ha, respectively, in the second growing season. The values of the relative yield loss (RYL) index for seed yield were 28.2% in the first growing season and 31.5% in the second growing season. Overall, white lupine growth and seed yield was significantly affected by the occurrence of weeds mostly at the early vegetative stages, resulting in the potential yield not being achieved due to weed competition. Future research on weed competition across several sites and years would be useful to define more clearly the critical period of weed control in white lupine.

Biomass Accumulation and Technical and Economic Efficiency of Potassium Sources Applied via Fertigation to Corn

To achieve high corn yield, optimal amounts of nutrients that can be extracted by the crop must be supplied at adequate proportions. Vinasse from sugarcane ethanol production can be applied as a soil fertilizer to corn crops in ethanol production plants. In this context, the present study compared the effects of mineral potassium fertilization with potassium chloride and organic fertilization with concentrated sugarcane vinasse on corn dry matter and grain yield and explored the technical and economic efficiency of these sources. The experiment was carried out at the experimental station of the Federal Institute Goiano, Rio Verde Campus, Brazil. The experiment followed a randomized block design in a 2 × 4 factorial scheme, with three replicates. The treatments comprised two sources of potassium, namely concentrated vinasse and potassium chloride, applied at four doses of potassium, representing 0%, 50%, 100%, and 200% of the recommended rate for corn. The dry matter accumulation of corn throughout the crop cycle, yield components at harvest, and technical and economic efficiency of the applied potassium sources were measured. Neither potassium dose nor its source affected leaf, stem, and aboveground dry matter accumulation at harvest. Regardless of the potassium source, the 100% dose produced higher cob dry mass, grain dry mass, grain dry mass per ear, grain yield, number of bags of 60 kg ha−1 produced per hectare, and harvest index. The agronomic efficiency of vinasse compared to potassium chloride was 68.5% at the 100% dose of the recommendation, showing enough potential as an organic fertilizer in corn crop.

Responses of yield, quality and water-nitrogen use efficiency of greenhouse sweet pepper to different drip fertigation regimes in Northwest China

Given water resources scarcity in Northwest China and the urgent need for the integration and optimization of scientific and technological resources in facility agriculture, this experiment explored the appropriate water and fertilizer management measures for greenhouse sweet pepper under fertilization in Northwest China. A two-year drip fertigation sweet pepper experiment was conducted in a solar greenhouse, with four irrigation levels (W1: 105% ETC, W2: 90% ETC, W3: 75% ETC, W4: 60% ETC) and four nitrogen levels (N1: 300 kg/ha, N2: 225 kg/ha, N3: 150 kg/ha, N4: 75 kg/ha). The results showed that above-ground dry matter accumulation (DMA), yield, harvest index (HI), and water use efficiency (WUE) of sweet pepper increased first and then decreased with the increase of irrigation/nitrogen amounts under the same nitrogen/irrigation levels. The partial factor productivity of nitrogen (PFPN) decreased significantly with the increase of nitrogen application rate, while it increased first and then decreased with the increase of irrigation level. The PFPN reached a peak at W2 level, despite no significant difference between W2 and W3 levels. With the increase of nitrogen application rate, soluble sugar and vitamin C content increased first and then decreased with a maximum at N3 level; nitrate content increased with the increase of nitrogen application rate, and there was no significant difference between N4 and N3 levels. The contents of soluble sugar and nitrate nitrogen decreased with the increase of irrigation amount, and they did not differ between W1 and W3 levels at N3 level; the vitamin C content increased first and then decreased with the increase of irrigation amount, reaching the maximum in W2 or W3 treatments. Considering the shortage of water resources in the study area, the W3N3 treatment (75% ETC, 150 kg/ha) could be recommended as the optimal drip fertigation strategy. Results showed that the optimal value of sweet pepper (the best confidence intervals of 85%) was achieved at the irrigation water and nitrogen amount of 78.2–80.8% ETC and 164.5–189.5 kg/ha, respectively. This study provides scientific basis for water and nitrogen management of high yield, quality, and benefit planting of facility sweet pepper in Northwest China.

Conservation tillage improves the yield of summer maize by regulating soil water, photosynthesis and inferior kernel grain filling on the semiarid Loess Plateau, China.

Poor inferior kernel grain filling is a challenge that limits summer maize yield. The effect and mechanism of conservation tillage on improving grain filling of inferior kernel in semi-arid rained areas remain uncertain and there has been little research on tillage management integrated with straw mulching to improve soil water content and photosynthesis in the Loess Plateau region. A 2 year (2019-2020) field experiment was established to study the impact of tillage practices on soil water content and summer maize root system morphology, photosynthetic capacity, inferior kernel grain filling, and grain yield. Treatments included reduced tillage (RT), no tillage (NT), and conventional tillage (CT). Under RT and NT, the final 100-kernel weight and maximum and mean grain filling rates were higher than CT. Reduced tillage and NT increased soil water content at the jointing stage, silking stage and grain filling stage in comparison with CT. They increased root system morphology and dry matter accumulation, net photosynthetic rate, transpiration efficiency, and stomatal conductance in comparison with CT, and they also decreased intercellular CO2 concentration, and they increased chlorophyll content and above-ground dry matter accumulation in comparison with CT. Reduced tillage and NT increased evapotranspiration of maize, and ultimately, increased grain yield by 17% and 14%, respectively, in comparison with CT. Conservation tillage could promote summer maize photosynthetic capacity and grain filling of inferior kernels by regulating soil water content and root system morphology. © 2021 Society of Chemical Industry.

Phosphorus Supply Increases Internode Length and Leaf Characteristics, and Increases Dry Matter Accumulation and Seed Yield in Soybean under Water Deficit

Phosphorus (P) addition ameliorates the adverse effects of water stress on the seed yield of soybean (Glycine max L.). Previous studies focused on the effect of P on root traits, but little information is available on changes to aboveground traits. In this paper, we show how P addition affects shoot traits and reduces the adverse effects of water stress on the yield. Two soybean genotypes, with contrasting aboveground architectures, were grown in pots to compare the canopy architecture, leaf traits, aboveground dry matter accumulation and yield under two water and three P levels. The addition of P to two soybean genotypes, one with a larger number of branches and greater leaf area on the branches than the other, showed that the increased leaf area distribution on the main stem and branches was associated with increased shoot and root dry weights, which were positively correlated with the number of filled pods, seed number and seed yield and negatively correlated with seed size at maturity under well-watered and cyclic water stress treatments. The leaf P concentration at 65 DAS (flowering stage) and leaf photosynthesis measured shortly after re-watering increased with P addition, while the leaf mass area on the main stem at 65 DAS and maturity and on the branches at maturity increased modestly with P supply and water stress. Evidence is presented that P addition can ameliorate the adverse effects of water stress on yield through increased leaf area, leaf function and aboveground shoot production. We conclude that the increased yields of soybean resulting from increased P and water supplies that were previously shown to be associated with increased root growth and function are mediated through increased shoot growth and function, particularly the greater number of sites for pod production.

Physiological analysis of growth and development of winter carinata (Brassica carinata A. Braun)

AbstractBrassica carinata is a non‐food, low‐carbon, none‐to‐low indirect land‐use change impact oilseed feedstock grown for sustainable biofuels, bioproducts, and high protein seed meal. Understanding carinata growth and development is critical to the development of best management practices for maximum productivity and profitability of double‐cropped farming systems. Field experiments were conducted during 2017–2018 (Year 1) and 2018–2019 (Year 2) winter–spring growing seasons in Quincy, Florida, to quantify the total aboveground dry matter accumulation (TDM), allocation, growth, nutrient uptake, and seed quality. The two carinata cultivars Avanza 641 and AX17012 accumulated 10826 and 9343 kg TDM ha−1 in Year 1 and 9655 and 10,642 kg TDM ha−1 in Year 2, respectively, at harvest maturity. The proportion of DM in the vegetative parts such as leaves and stems decreased, and the DM in reproductive structures such as silique walls and seeds increased with maturity. Seed yield (SY) was similar between cultivars but differed between years with Year 1 (2732 kg ha−1), producing 29% greater SY than Year 2 (1929 kg ha−1). Carinata primary stem has 17–20 leaf nodes, with 75%–88% of the axillary meristems producing primary and secondary branches. Crop growth rate (CGR) increased from vegetative to pod development for both cultivars in Year 1, while in Year 2, AX17012 and Avanza 641 attained maximum CGR at the pod development and bolting/flowering stages, respectively. Maximum seasonal nutrient uptake in leaves, stems, and siliques generally occurred in the early, mid, and late season, respectively, in both years. Seed weight, oil, monounsaturated fatty acids, C18:3, C20:1, and C22:1 concentrations increased with plant age, whereas protein, glucosinolate, polyunsaturated fatty acids, saturated fatty acids, C18:1, and C18:2 concentrations decreased with plant maturity. These results can be used for crop modeling to predict growth, development, and yield and aid in developing in‐season decision support tools.

Combined ability of salicylic acid and spermidine to mitigate the individual and interactive effects of drought and chromium stress in maize (Zea mays L.)

Application of the growth regulator salicylic acid (SA) and the polyamine spermidine (Spd) can be used to manage various plant abiotic stresses. We aimed to evaluate the sole and combined effects of SA and Spd on maize (Zea mays) under individual and combined drought and chromium (Cr) stress. Drought, Cr, and drought + Cr treatments caused oxidative stress by inducing higher production of reactive oxygen species (H2O2, O2−), enhanced malondialdehyde content and increased relative membrane permeability. Increased oxidative stress and higher Cr uptake in the host plant reduced the content of carotenoids, other photosynthetic pigments and protein, and changed carbohydrate metabolism. Combined drought + Cr stress was more damaging for the growth of maize plants than the individual stresses. Exogenous treatments of SA and Spd alleviated the adverse effects of drought and Cr toxicity, reflected by accumulations of osmolytes, antioxidants and endogenous polyamines. Single applications of Spd (0.1 mM) increased plant height, shoot fresh weight, leaf area, above-ground dry matter accumulation and polyamine content under drought, Cr, and drought + Cr stress conditions. However, the combined treatment SA + Spd (0.25 mM + 0.05 mM) was more effective in increasing protein and water contents, photosynthetic pigments, and carotenoids. The same treatment increased Cr tolerance in the maize plants by decreasing uptake of this heavy metal from root to shoot. The SA + Spd treatment also decreased oxidative stress by promoting antioxidant enzyme activities, and enhanced levels of proline, soluble sugars, and carbohydrate contents under individual and combined stress conditions. Results indicate that the combined half-dose application of SA + Spd may be utilized to boost the tolerance in maize under individual as well as combined drought and Cr stress conditions.

Critical period for seed number determination in soybean as determined by crop growth rate, duration, and dry matter accumulation

• We used two independent approaches to identify the beginning and end of the critical period for seed number determination in soybean. • Critical period for seed number determination occurs during the R3-R6 phase. • Seed number was related to biomass accumulation during the critical period. • Accumulated biomass is a better predictor of seed number than crop growth rate or duration alone. Seed number (SN) is positively associated with aboveground dry matter (ADM) accumulation in most crop species. In soybean, there are discrepancies among studies relative to the start and end of the critical period for seed number determination. The objective of this study was to more precisely identify those two stages. To do so, we followed two approaches: (i) analyses of experimental data where differences in SN occurred as a result of variation in crop growth due to weather and management practices and (ii) review of published experiments where soybean was subjected to artificial stresses during specific crop phases. Following the first approach, we analyzed the relationships between SN versus ADM accumulation and its components, crop growth rate (CGR) and duration, for different reproductive phases using data from experiments that portrayed a wide range of environments and management practices. In the second approach, we compared SN values in stressed versus non-stressed treatments. Accumulated ADM during the R3 to R6 phase explained ca. 70 % of the variation in SN across experiments. The CGR during R3-R6 was also a good predictor of SN, but it had lower explanatory power compared with accumulated ADM, because CGR did not account for changes in duration of critical period across experiments. Review of published data, wherein soybean crops were subjected to artificial stresses during different reproductive phases, confirmed that the R3-R6 phase is a critical phase for SN determination in soybean. Key findings of this study were: (i) critical period for SN determination in soybean occurs during the R3-R6 phase and (ii) accumulated ADM during the critical period is a better predictor of SN compared with CGR because it accounts for differences in the duration of the critical period as a result of weather and management.

Effect of bentonite as a soil amendment on field water-holding capacity, and millet photosynthesis and grain quality

A field experiment was conducted in a semi-arid region in northern China to evaluate the effects of bentonite soil amendment on field water-holding capacity, plant available water, and crop photosynthesis and grain quality parameters for millet [Setaria italic (L.) Beauv.] production over a 5-year period. Treatments included six rates of bentonite amendments (0, 6, 12, 18, 24 and 30 Mg ha−1) applied only once in 2011. The application of bentonite significantly (P < 0.05) increased field water-holding capacity and plant available water in the 0–40 cm layer. Bentonite also significantly (P < 0.05) increased the emergence rate, above-ground dry matter accumulation (AGDM), net photosynthesis rate (Pr), transpiration rate (Tr), soil and plant analysis development (SPAD) and leaf water use efficiency (WUE). It also increased grain quality parameters including grain protein, fat and fiber content. Averaged over all the years, the optimum rate of bentonite was 24 Mg ha−1 for all plant growth and photosynthesis parameters except for grain quality where 18 Mg ha−1 bentonite had the greatest effect. This study suggests that bentonite application in semi-arid regions would have beneficial effects on crop growth and soil water-holding properties.