Thermal Sum Research Articles

Environmental factors affecting tomato growth for industrial processing in the Brazilian Savannah of Goiás State

This study investigates the meteorological variables exerting the most significant influence on the growth and productivity of four tomato hybrids cultivated for industrial processing in the Brazilian Savannah of Goiás State. Data on morphological and meteorological variables were collected in five locations (Hidrolândia, Itaberaí, Palmeiras de Goiás, Piracanjuba, and Silvânia) during the year 2020. Morphological characteristics assessed included plant height, number of branches, and leaf area index (LAI). Meteorological variables considered were average air temperature, global solar irradiance, thermal sum, and soil water availability. Pearson correlations, canonical correlations, and multivariate Stepwise regression were employed to analyze the relationships between morphological and meteorological variables. The study revealed that soil water availability significantly impacts tomato crop development, indicating the need for improved irrigation management. Adequate irrigation management contributed to an 86.1% increase in plant height and a 79.7% boost in leaf area index, while average air temperature influenced a 34% increase in the number of branches. In conclusion, proper irrigation management is crucial for enhancing tomato crop growth and development and optimizing water use.

Thermal sum accumulated in development stages of tomato crop for industrial processing

Tomato crop for industrial processing is very sensitive to weather variations. Therefore, the objective of this research was to quantify the duration (days and thermal sum) of each developmental stage of different hybrids in two different planting date. For this, 12 commercial hybrids were evaluated: H-1301, BS-P0033, CVR-8161, HM-7885, CVR-6116, HM-7883, H-1536, CVR-2909, TPX-26856, CVR-8126, CTI-35 and N-901, in Abadia de Goiás, Brazil, planted on 03/31/2020 and 05/26/2020. Experimental area with 3,120 m2, 4 blocks with 12 experimental plots each (12 hybrids), and each plot, formed by 3 double planting lines of 10 m, spaced 0.6 m x 1.2 m, with plants every 0.37 m, totaling 27 plants per line and 162 plants per plot. Plant phenology was monitored daily: phase I (planting to set), phase II (set to flowering), phase III (flowering to beginning of maturation) and phase IV (IVa beginning of maturation up to 50% of mature fruits and phase IVb (from 50% to 90% of mature fruits). The results show, on average of all hybrids, thermal sum of 1,394 and 1,364 oC obtained in 124.6 and 116.1 days of cycle, in first and second cycle, respectively. In first cycle, there was a difference in thermal sum between the hybrids in stage IV and in total cycle, which hybrids BS-P0033, CVR-8161, HM-7885, HM-7883, CVR-2909 and TPX-26856 accumulated from 81.29 to 112.88 oC in 6 to 9.3 days to complete maturation, while other hybrids accumulated from 122.85 to 148.11 oC in 10.3 to 13 days. The hybrids BS-P0033, CVR-8161, HM-7885 and HM-7883 had a shorter total cycle duration from 1,334.21 to 1,379.98 oC (119 to 123 days), while other hybrids variated of 1,391.45 to 1,437.05 oC (124.3 to 129 days). The stages of setting, vegetative and beginning of maturation up to 50% of ripe fruits, showed variation in thermal sum and duration of phase, depending on planting date. For the first cycle, the duration of average vegetative stage was 21.7% longer, accumulating 34.1% more oC, compared to the second cycle, providing greater plant height (43.8%) and higher productivity (19.8%). This shows that is need to change irrigation management strategy between transplanting date and crop development stages, making irrigation adjustments by thermal sum and not by number of days for development stage.

Carpochron: a concept for the time interval between the appearance of fruits in consecutive harvests

The aim of this research was to estimate the base temperature for the appearance of fruits at harvest point in the strawberry and to propose a concept to represent the time required for the appearance of fruits in consecutive harvests. The experiment was conducted in 2021 in four seedling transplanting seasons: May (season 1), June (season 2), July (season 3) and August (season 4) of two cultivars: Fronteras and Merced. Twenty-four consecutive fruit harvests were carried out from September 9, 2021, to December 1, 2021, when the number, length (cm), diameter (mm), and fresh weight of the fruits (g) were evaluated. The base temperature for the fruit emission of the strawberry was calculated using the method of the smallest mean square error. Carpochron was estimated at each season and for each cultivar, obtaining a simple linear regression between the number of fruits and the accumulated thermal sum (ºC day) and the number of days after transplanting (DAT), using as base temperature the one estimated in this work. The base temperature for the appearance of consecutive fruits at the harvest point in the strawberry is 11ºC. Carpochron increases with the delay of the transplanting season and the values ranged from 81.97ºC fruit day to 144.93ºC fruit day for cultivars Merced and Fronteras.

The clockwork of spring: bud dormancy timing as a driver of spring leaf-out in temperate deciduous trees

The initiation of spring leaf-out is a critical determinant of the growing season in trees, affecting primary production and species interactions in forest ecosystems. Variations in the timing of leaf-out among tree species are linked to their differential progression of bud dormancy. However, identifying reliable markers for bud dormancy has been challenging, leaving the connection between the timing of autumn leaf senescence, bud dormancy and spring leaf-out unclear. To test whether species initiating dormancy release earlier also exhibit earlier leaf senescence in autumn and earlier leaf-out in spring, we estimated the dates of peak dormancy depth (PDD), senescence timing and spring leaf-out across various species, locations and experimental conditions in Central Europe. PDD was defined as the date when the maximum thermal sum was required for leaf-out, whereas leaf senescence was assessed through the decrease in leaf greenness. Our findings reveal that PDD timing is a more accurate predictor of species-level differences in spring leaf-out dates than the timing of leaf senescence, the latter being a poor proxy for PDD. The observed temporal asynchrony between PDD and senescence was linked to dormancy induction showing species-specific sensitivity to temperature variations. Conversely, the timing of leaf senescence showed a consistent reaction to temperature changes across all species. These findings suggest that the physiological processes within buds and leaves during autumn are governed by distinct environmental cues, with the bud dormancy process serving as a more reliable predictor of spring phenological differences among forest tree species than does autumn leaf senescence.

Mowing and nitrogen management guidelines for superior rice ratoon yields

Forage-grain ratoon rice (FG-RR) is a dual-cropping system, with forage harvested in the initial season and grain during the regeneration phase. While it is known that the timing of mowing and nitrogen (N) fertilization are key drivers that influence FG-RR production, physiological mechanisms ensuing mowing and N fertilizer application remain unclear. We conducted field experiments in 2021 and 2022 to investigate the yield and growth characteristics of ratooned crops (RC) under various mowing treatments (heading, milk-ripening, dry-ripening and maturity) using three N levels (135, 270, and 405 kg ha−1), two rice genotypes, Taoyouxiangzhan (TYXZ) and Liangyou 6326 (LY6326). Our results demonstrate a significant increase in ratoon yield when mowing occurred at heading or milk-ripening stages compared with maturity, with a yield increase of 2.2-fold when mowing occurred at heading. Early mowing stages increased stubble biomass (up to 73 %) and non-structural carbohydrate (up to 198 %) compared with that at maturity. Mowing at heading or milk-ripening improved accumulated temperature and light exposure, and when coupled with higher N application (270 kg ha−1 N), amplified ratoon ability to recover. Collectively, these factors raised leaf area index, canopy light interception and biomass. Hierarchical partitioning analysis underscored the substantial yet indirect influence of environmental drivers of ratoon yield, alongside a direct driver of growth, particularly thermal sum. We conclude that mowing at heading and milk-ripening with 270 kg ha−1 N elicits optimal ratoon yield with forage production, although further studies are required to determine how these guidelines vary across environments.

Crescimento da linhaça oleaginosa descrito por modelo não linear logístico

ABSTRACT Knowledge on plant-atmosphere interactions is essential to understand the growth and development of agricultural crops. Thus, fitting growth curves is an important methodology to model plant growth and phenological stages. The study aimed to describe the growth of four oilseed flax materials cultivated in six agricultural years and with different sowing dates through the nonlinear logistic model. Nine experiments were carried out in Curitibanos, SC, Brazil, between 2014 and 2020, considering different sowing dates. Throughout the crop cycle, the number of leaves, number of secondary stems, plant height and total dry mass were measured. Nonlinear logistic model was fitted to the data, with the growth variables as the dependent variables and the accumulated thermal sum as the independent variable. Model fit and parameter estimation were obtained by ordinary least method, using a Gauss-Newton algorithm. The goodness of fit was measured by intrinsic and parametric nonlinearity, adjusted coefficient of determination, random standard error, standard deviation of fit, Akaike information criterion, and Bayesian information criterion. The performance of the nonlinear logistic model differed between the varieties and cultivars studied, in different years and sowing times. However, the use of the nonlinear logistic model improves inferences about the growth of oilseed flax, and the estimates of its parameters and critical points allow a biological and practical interpretation to assist in crop planning. Furthermore, the study suggests that the oilseed flax cycle is directly related to genotype × environment interactions, and when sown at later times, the materials tend to shorten their cycle.

Simulation of oat yield through biological and environmental variables for reducing fungicide application and increasing interval from application to grain harvest

Simulation models based on biological and environmental variables allow the analysis of scenarios in proposing more sustainable management. The objectives is to identify potential biological and environmental variables for inclusion and validation of multiple linear regression model for yield simulation and analyze scenarios that promote yield and satisfactory control of foliar diseases, with longer intervals between the last fungicide application and the grain harvest. The study was conducted in 2015, 2016, 2017, in Augusto Pestana, RS, Brazil. The soil is classified as Oxisol and the climate of the region as Cfa type, by the Köppen classification. The experimental design was randomized blocks, with three replications, in a 22 x 4 factorial, for 22 oat cultivars (10 recommended and 12 no longer recommended) and 4 fungicide use conditions (no application; one application 60 days after emergence (DAE); two applications, 60, 75 DAE; and three applications, 60, 75, 90 DAE. In 2015 and 2016, the fungicide FOLICUR® CE was used, and in 2017 PRIMO®, at a dosage 0.75 and 0.3 liters ha-1, respectively. Necrotic leaf area, rainfall depth, mean minimum and maximum temperatures, thermal sum, and crop cycle period (days) are potential variables by the Stepwise technique in the simulation of oat yield, validating the use of the multiple linear regression. The condition with three fungicide applications, at 60, 75, 90 DAE, resulted in satisfactory foliar disease control and grain yield, while maintaining a long interval between the last fungicide application and the grain harvest, thus improving the safety of the product obtained

Leaf appearance rate and phyllochron on millet sowing dates

The objective of this study was to determine the leaf appearance rate and phyllochron as affected by millet sowing dates. The experiment was conducted with six sowing dates (11/28/2019, 12/03/2019, 12/10/2019, 12/17/2019, 12/30/2019 and 01/14/2020). The sowing was performed in plots with six rows of 2 m length and spacing of 0.25 m between rows. After emergence, for each sowing date, five plants were marked and the number of leaves was counted twice a week until flowering. For each plant relative to each sowing date (30 plants), the number of leaves (NL), leaf appearance period (LAP, in days), accumulated thermal sum (TSa, in ºC day), leaf appearance rate (LAR, on days leaf-1) and phyllochron in °C day leaf-1 were determined. Among the sowing dates, there is no variation in the number of leaves, with an average of 18.07 leaves. LAP varies between 49 and 88 days, TSa between 697.57 and 1299.47 °C day, LAR between 3.26 and 5.40 days leaf-1, and phyllochron between 45.05 and 80.81 °C day leaf-1. Millet shows better vegetative development (lower LAP, TSa, LAR and phyllochron) in early sowing (11/28/2019, 12/03/2019 and 12/10/2019) compared to later sowing (12/17/2019, 12/30/2019 and 01/14/2020).

Growth curve pea in different seasons as a function of accumulated thermal sum

Growth curve pea in different seasons as a function of accumulated thermal sum

Pasture and grassland productivity and foliar elongation of wheatgrass in Southern Patagonia

The aim of this work was to show the relationship of the productivity of a pasture and grassland, the living and dead material, and the foliar elongation of wheatgrass with the soil moisture and the thermal sum in Southern Patagonia (Argentina). During the years 2015/16 (Year 1) and 2016/17 (Year 2), in closures excluded from grazing, the plant height, the accumulated aerial biomass (AAB) and the daily growth rate (DGR) of a mixed pasture and grassland were determined monthly from October to February. The forage harvested from the pasture was characterized in live (LM) and dead material (DM), and the live AAB was calculated. In selected wheatgrass plants, the leaf elongation rate (LER) was determined. Soil moisture (SM) was measured and the thermal sum (TS) was calculated. The AAB was analyzed using a factorial arrangement in a completely randomized design. The results were subjected to ANVA with repeated measures analysis and the means were adjusted with the Tukey-Kramer test. DGR, LM, and LER were related to SM and TS by multiple regression analysis. In both Year 1 and Year 2 and same months the AAB of the pasture exceeded the forage accumulated by the grassland. The LM and the LER varied according to the changes in the SM, and the TS explained the variations of the parameters described, which should be considered when developing future management strategies in this type of pasture.

Summer litter decomposition is moderated by scale‐dependent microenvironmental variation in tundra ecosystems

Tundra soils are one of the world's largest organic carbon stores, yet this carbon is vulnerable to accelerated decomposition as climate warming progresses. The landscape‐scale controls of litter decomposition are poorly understood in tundra ecosystems, which hinders our understanding of the global carbon cycle. We examined the extent to which the thermal sum of surface air temperature, soil moisture and permafrost thaw depth influenced litter mass loss and decomposition rates (k), and at which spatial thresholds an environmental variable becomes a reliable predictor of decomposition, using the Tea Bag Index protocol across a heterogeneous tundra landscape on Qikiqtaruk–Herschel Island, Yukon, Canada. We found greater green tea litter mass loss and faster decomposition rates (k) in wetter areas within the landscape, and to a lesser extent in areas with deeper permafrost active layer thickness and higher surface thermal sums. We also found higher decomposition rates (k) on north‐facing relative to south‐facing aspects at microsites that were wetter rather than warmer. Spatially heterogeneous belowground conditions (soil moisture and active layer depth) explained variation in decomposition metrics at local scales (< 50 m2) better than thermal sum. Surprisingly, there was no strong control of elevation or slope on litter decomposition. Our results reveal that there is considerable scale dependency in the environmental controls of tundra litter decomposition, with moisture playing a greater role than the thermal sum at < 50 m2 scales. Our findings highlight the importance and complexity of microenvironmental controls on litter decomposition in estimates of carbon cycling in a rapidly warming tundra biome.

Regional climate affects habitat preferences and thermal sums required for development of the Eurasian spruce bark beetle, Ips typographus

In recent years, the outbreaks of the Eurasian spruce bark beetle (Ips typographus) have become more frequent and severe, while temperatures have been rising. Our understanding of the consequences of climate warming can be improved by comparing the performance of I. typographus between geographical regions with different climates. We applied that approach by placing out Norway spruce logs at sites selected along a 1300 km north–south gradient in Sweden to study the effect of regional climate and microclimate on I. typographus. To obtain a microclimatic gradient at each site, we placed the logs at sun-exposed edges and in the shaded inner forest (10 m or 50 m from stand edges). We assessed the probability of colonisation of I. typographus and the thermal sums required for complete development.The species’ habitat preferences differed along the climate gradient including six geographical regions: in cooler regions, a higher proportion of sun-exposed logs was colonised in comparison to the shaded ones, while that difference was much smaller in warmer regions. The thermal sum needed for development tended to increase with warmer regional climate. Seasonal thermal sum exceeded the requirements for development of two generations per year in all three shade levels in the warmest region while in the coldest region two generations were only possible in some of the sun-exposed logs.Outbreaks of I. typographus are more frequent and severe in regions with a warmer climate, and our study reveals two explanations for this: first, I. typographus has more suitable breeding sites in warmer regions, as shaded logs inside the forest offer additional suitable habitat; second, the potential population growth increases with the probability of completing two fully established generations per year. We recommend that after storm-fellings, wind-felled trees are removed before they are colonised by I. typographus to decrease the outbreak risk. The observed difference in habitat preferences between geographical regions implies that, in cooler sites in the north, it is enough to remove recently wind-felled spruces that are sun-exposed, such as along edges, while in the south, also trees in more shaded conditions inside forests are a suitable substrate for I. typographus. In a warming climate, the increased risk and severity of I. typographus outbreaks is a factor making it less attractive to use Norway spruce in forestry.

Citrus crop performance and fruit quality in response to different scion-rootstock combinations

Aim of study: To address diversification of citrus cultivars to increase the variety and profitability of orchards to adapt them to environmental changes. Area of study: State of São Paulo, a subtropical region of southeastern Brazil. Material and methods: The study evaluated the phenological intervals, thermal sum, vegetative and productive performance, and fruit quality of the sweet orange cultivars ‘Rubi’ (R), ‘Lue Gin Gong’ (LGG) and ‘Valencia Delta Seedless’ (VDS) grafted onto 'Rangpur' lime (RL) and 'Swingle' citrumelo (SC). The field experiment was conducted over consecutive growing seasons 2018-2021. Main results: The duration of the phenological intervals was little influenced by the rootstocks. The harvest time was approximately 245 days after anthesis (DAA) for R, 402 DAA for LGG, and 407 DAA for VDS, regardless of rootstock. Scion cultivars grafted onto RL showed larger canopy volumes and greater weight, length, and diameter of fruits than those of SC trees, and the combinations with SC were more productively efficient than RL due to lower canopy volume. The R scion cultivar presented superior yield performance and fruit colouration than LGG and VDS. The physicochemical quality of the fruits showed improved results with the combinations of LGG/RL, LGG/SC, VDS/RL, and VDS/SC. Research highlights: These results may be useful when planning the diversification of scion/rootstock combinations for new orchards, identifying dual-market orange cultivars for industrial processing and natural consumption, and determining the combinations that are better adapted to undesirable climatic conditions.

Liquid Source Nitrogen as a More Sustainable Technology for oat Fertilization with Computational Simulation Resource

Purpose: The objective of the study is to validate the technology of liquid nitrogen source by spraying of foliar absorption in comparison to the standard source urea of root absorption in the oat crop. Adapt the fuzzy logic model and training an artificial neural network to simulate oat productivity, under conditions of nitrogen use with the combined action of rainfall and thermal sum accumulated during the crop cycle. Method/design/approach: The study was conducted in Augusto Pestana, RS, Brazil, in a randomized block design with four replications in a 2x4 factorial, for 2 nitrogen sources (liquid and solid) with 4 doses (0, 30, 60 and 120 kg ha-1), respectively. Solid (urea) and liquid (N-Top®) nitrogen sources were applied at the phenological stage of expanded oat fourth leaf. Results and conclusion: The liquid source nitrogen technology presents results similar to the use of the standard urea source, confirming the possibility of using the nutrient by foliar absorption. The simulation of grain yield by fuzzy logic with the input variables nitrogen dose, thermal sum and precipitation is not adequate for the formulated rule base. The input variables used in the artificial neural network proved to be appropriate in the simulation of oat productivity, with consistent simulation results. Originality/value: unprecedented research that seeks to validate the technology of foliar nitrogen absorption in real conditions of oat cultivation in guaranteeing productivity and less environmental damage. And the use of artificial intelligence as a resource to simulate grain productivity involving biological and environmental indicators in the main oat producing region of Brazil.

Estimate of chickpea production (Cicer arietinum L.) as a function of plant phenology

Chickpea is a crop of the indeterminate type which can be an advantage to estimate in advance the production of this crop. The lack of water, cold or heat are the most limiting factors for the success of this culture; in the emergency phase, situations of waterlogging or extreme drought lead to an irregular installation of the culture, on the other hand, drought, excess water and extreme heat during the reproductive period, cause floral abortion and/or shorter cycles, and consequently, smaller income. Chickpea yield essentially depends on the number of seeds per unit area, which in turn depends on the length of the reproductive period. This is a problematic situation that proves the complexity of estimating the yield in leguminous crops in relation to species of determined habit. We try to know the dates of development of chickpeas, namely when the vegetative apex becomes reproductive (Beginning of Flowering, BF) and when the last flower of the apex no longer develops (End of Flowering, EF), this knowledge is fundamental anticipate and estimate the productive potential. Portugal is a country with a typical Mediterranean climate that has high capacity to produce grain legumes and the chickpea breeding program started at Plant Breeding Station, Elvas, Portugal in 1986. Since this data we have determined the dates of the BF and EF and, due to the difference between the two, the Reproductive Period (RP); the longer this period, the greater the number of pods and seeds per plant, and, as a consequence, greater final productions. In this way, over the course of 24 years, we have been recording the dates of entry into flowering and the end of flowering according to the thermal sum in Growing Degree Days (GDD) of by genotype, by trial and by year. In this analysis it was found that the BF is achieved when the sum of the GDD reaches 757 ºC, for maximum temperatures of 23 ºC, and the EF for sums of 1224 ºC and maximum temperatures of 30 ºC, that is, when temperatures above 28 ºC are registered, for two or three days in a row, is an indicator that the EF is approaching. It may happen later if precipitation occurs when the temperature reaches those values, but it varies from genotype to genotype. The new varieties, Elipse, Electra, Eleia, Eladir and Elfo confirm this situation, with the ELEIA variety standing out earlier in flowering.

Portulaca oleracea L.: genotypes phenology and thermal sum in tropical climate

Portulaca oleracea L., known as purslane, is an unconventional food plant rich in nutrients and medicinal properties, with potential for consumption and commercialization. The objective was to describe phenological stages of purslane based on BBCH (Biologische Bundesantalt, Bundessortenamt and Chemische Industrie) scale and thermal sum at different times. Evaluations were made from two genotypes, the Golden variety and an access. Plants were observed during six consecutive periods, interspersed every two months. Thermal sum and base temperature were obtained considering the average temperature from seedling emergence to flowering and dispersion of the first capsule in 50% of the plants. The phenological cycle of Purslane based on the BBCH scale shows seven main stages, subdivided into secondary stages: germination (0); leaf development on the main branch (1); development of lateral branches (2); development of flower buds (5); flowering (6); seed dispersal (8); and senescence (9). The lower base temperatures (Tb) determined to flowering were 10 to 15 ºC for the variety Golden and access, respectively, since for seed dispersal, Tb was 9 and 13 ºC, respectively. Thermal requirements for Golden variety are 421.3 GD for flowering and 644.2 GD for seed dispersal, while for access they are 239.7 and 407.0 GD, respectively. Purslane as a food plant can be produced throughout the year in tropical region and may be best used if harvested until the plants reach 12 or 10 leaves.

Índice de nutrição nitrogenada e morfogênese em papuã na Depressão Central do Rio Grande do Sul

ABSTRACT: This study assessed the nitrogen nutrition index, morphogenic characteristics and tiller structure of Alexandergrass (Urochloaplantaginea (LINK) Hitch) pasture submitted to different nitrogen (N) levels (zero, 150 or 300 kg ha-1 of N). The experimental design was entirely randomized with repeated measures arrangement. The experimental animals were Angus heifers under rotational stocking grazing method. The number of animals was variable to keep 30±5 cm post-grazing sward height. Nitrogen nutrition index increased linearly according N levels (Ŷ = 59.8 + 0.1216N; P < 0.0001; r²=0.53). The leaf appearance rate adjusted to a positive linear regression model according the thermal sum (TS) with zero of N (Ŷ0N = 0.0077 + 0.0000087TS; P = 0.0308; r² = 0.72) and 150 kg ha-1 of N (Ŷ150N = 0.0020 + 0.000021 TS; P = 0.0022; r² = 0.92). The use of 300 kg ha-1 of N did not alter the leaf appearance rate (0.0124 leaf degree-days-1). The use of up to 300 kg ha-1 of N increases the Alexandergrass nitrogen content. The leaf appearance rate in Alexandergrass is modified using N while the morphogenic characteristics leaf expansion, stem expansion, phyllochron, leaf lifespan, leaf elongation duration and tiller structure are not altered by N utilization.

Plastocrono, fenologia e produção de ervilha verde em diferentes épocas de cultivo

ABSTRACT Pisum sativum L. is a multi-purpose crop. The duration of its vegetative and reproductive periods is determined by a combination of temperature and humidity and genotype response to these conditions. To minimize the loss of productivity due to adverse conditions in sensitive periods of the crop, we evaluated the phenological development and production of Pisum sativum L. in different growing seasons. We used a randomized block design, and the experiments were conducted across five growing seasons, with four replications and eight plants per experimental unit. The variables analyzed were as follows: plastochron, number of days to start flowering, full flowering, and beginning of harvest, the accumulated thermal sum to start flowering, full flowering, and beginning of harvest, and the number of pods, pod mass, and total productivity per unit area. The analysis of variance was performed, and the mean values of the data were compared using the Scott-Knott test. Principal component analysis was also performed from Pearson’s correlation matrix of phenological and production variables. In seasons 1, 4, and 5, the plants reached full flowering earlier, and the pod mass was considerably lower, resulting in lower yields. Seasons 2 and 3 were the most productive and showed lower results for plastochron, less thermal sum until full flowering, and a shorter photoperiod, which, combined with low temperatures during the growing season, resulted in a longer cultivation cycle.

NUTRITIONAL ACCUMULATION FOR SALAD AND ITALIAN TOMATOES GROWN IN A PROTECTED ENVIRONMENT

Tomato cultivation in a protected environment is an important tool for increasing yield, quality, and regularity of production. However, nutrient imbalance in this production system can lead to short-and long-term losses. This study aimed to characterize plant growth and nutrient accumulation and export of two tomato hybrids of the Salad (‘Stella TY’) and Italian (‘HS 1188’) groups in a protected environment and determine the accumulated thermal sum. The treatments consisted of evaluation times. Dry mass and nutrient accumulation could be determined by a sigmoidal non-linear model for both hybrids grown in the protected environment. The cumulative nutrient order was K > Ca > N > S > Mg > P > Mn > Zn > Fe > Cu > B for ‘Stella TY’ and K > N > Ca > S > P > Mg > Mn > Fe > Zn > Cu > B for ‘HS1188’, with yields of 105.7 and 103.4 t ha−1, respectively. The accumulated thermal sum was 1851.7 degree days at 126 days after transplanting (DAT).

Evaluating crop models to assess rice yield potential in Argentina

Due to the high concentration of the rice production in Asia, the study and comprehension of rice producing chains outside this continent are key to guarantee the global food security. The objectives of this study were to validate the SimulArroz and ORYZA v3 crop simulation models for rice production in Argentina, estimate the yield potential (Yp) for different sowing dates with both models, and estimate how much Argentina can increase rice production in the current agricultural area by reducing the yield gap. Two contrasting rice models (ORYZA v3 and SimulArroz) were used. Besides both are mechanistic models, Simularroz model requires fewer coefficients than ORYZA v3,. which may increase the systematic error. The coefficient of determination between simulated and measured values was at least 0.74 for grain yield and 0.97 for phenology. RMSEn values for phenology ranged from 5.7% to 9.4%. Both models simulated grain yield accurately at high yield levels (>13 ​Mg ​ha−1) with an RMSE <0.5 ​Mg ha-1. The average irrigated rice Yp for subtropical Argentina estimated by the SimulArroz model ranged from 3.8 to 15.6 ​Mg ​ha−1, and from 7.6 to 14.3 ​Mg ​ha−1 in the ORYZA v3. The differences in the Yp between the models were due to different approaches in the calculation of thermal sum and radiation use efficiency. The increase in the rice production in Argentina if the fields close the exploitable gap (80% of the Yp) would be 42% of the current total rice production or 916,091 ​Mg annually.