Crop Cycle Length Research Articles

Effect of Swathing or Direct Combining on Yield, Seed Losses and Costs of Camelina

Camelina is an interesting crop and producers must adopt cultural practices to achieve the highest yield and oil content possible. Considering the size of the seed, the harvesting phase is crucial to reduce losses and maximize income. Furthermore, in recent years, with the worsening of climatic conditions due to global warming, crop management can no longer follow the classic seasonality but must adapt to new climatic conditions. The possibility of double cropping, that is the process of producing two crops in a single season, allows multiple advantages such as weed control, greater remuneration, and less exposure to bare soil which determine greater resilience of the production system. To enable this, especially in recent years, even a few days of difference in the cultivation phases can guarantee the success of double cropping. For these reasons, the authors compared two different harvesting strategies: direct combining at full maturity (DC); swathing + combining at full maturity (SW). The working performance, cost, and seed losses associated with each harvesting method were calculated. The results highlighted how SW reduced the crop cycle length by 11 days, did not influence seed losses and crop yield but showed lower performance and higher cost with respect to DC.

Efficacy of Azadirachtin in the Integrated Management of the Root Knot Nematode Meloidogyne incognita on Short- and Long-Cycle Crops

Activity of azadirachtin on phytoparasitic nematodes has been documented for some decades, but the relationship between its nematicidal efficacy and crop cycle length has not yet been clarified. This study aimed to assess the efficacy of an azadirachtin-based nematicide, for controlling the infestation of the root-knot nematode Meloidogyne incognita, on the short- and long-cycle crops, lettuce and tomato, respectively. Experiments on lettuce and tomato were carried out in a greenhouse infested by M. incognita, including non-treated soil, or treated with the nematicide fluopyram, as controls. In the experiment on the short-cycle lettuce crop, the azadirachtin product effectively suppressed M. incognita infestation and increased crop yield, without significant differences from fluopyram. In the tomato crop, both azadirachtin and fluopyram were not able to control nematode infestation, but resulted in significantly higher yields. Data from this study indicated that azadirachtin can be a valid alternative to fluopyram and other nematicides, for root-knot nematode control in short-cycle crops. Integration of azadirachtin with a synthetic nematicide or nematode-suppressive agronomical techniques, should be more suitable to long-cycle crops.

Assessment of Genetic Diversity in Plantain (Musa paradisiaca L) Using Yield-Related Agro-Morphological Traits and Microsatellite Markers

Background and Objective: Plantain (Musa paradisiaca L) remains one of themost important staple food crop and perhaps, one of the oldest cultivated fruit tree crop in the humid tropics of Africa, Central Asia, South America and the West Indies.Fourteen (14) elite plantain cultivars were evaluated for genetic diversity using agro-morphological yield related attributes and simple sequence repeat (SSR) markers.
 Materials and Methods: Six (6) microsatellite markers that showed distinct fragments varying from 50 bp to 3.0 Kbp in size of polymorphic bands were selected and used for molecular characterization and fingerprinting, while agro-morphological (yield–related) attributes assessed included bunch weight, number of hands/bunch, number of fingers/hands, number of fingers/bunch, harvest interval, length of plant cycle, pulp hardness and pulp to skin weight ratio of the elite plantain cultivars.
 Results: The total number of amplified bands (TNB), mean percentage polymorphism (%P), mean polymorphic information content (PIC), average marker index (MI) and mean gene diversity for the SSR assay were 59, 70.24%, 0.79, 3.74 and 0.832 respectively. Results of agro-morphological fingerprint study revealed a significant variations in terms of the bunch weight, number of finger per hands/bunch, number of fingers per hand, number of fingers /bunch, harvest interval, length of crop cycle, pulp hardness and pulp/wt. ratio all showed significant variations among the cultivars. The distribution of the elite cultivars along with the principal components showed cluster pattern of distribution within the study location. Principal component analysis revealed four principal components contributing 99.91% to the observed morphological variations while analysis of molecular variance revealed 96.00% contributed by molecular characteristics to observed variations. The yield displayed revealed significant contributions of bunch weight, fingers/hand and fingers/bunch as the main indices for plantain yield. The dendrograms for both morphological and molecular characteristics delineated the cultivars into four distinct cluster groups and subgroups each varying in genetic distance.
 Conclusion: These good cultivars can be exploited for the improvement of low yielding cultivars in other region to increase and improve plantain yield, promote food security and income generation especially under the present economic realities where food security is threatened by the global food crises and declining crop productivity.

Crop Cycle Length Determines Optimal Transplanting Date for Seedlings from Hybrid True Potato Seeds

AbstractThe technology of hybrid breeding in diploid potatoes creates opportunities to design novel and improved cultivation systems based on hybrid true potato seeds. A promising cultivation pathway to produce seed or ware tubers is by transplanting greenhouse-raised seedlings into the field. This study explored the effects of transplanting date and seedling age on tuber yield, using greenhouse-raised seedlings. Field trials with experimental hybrid genotypes were conducted in three consecutive years. In 2017 and 2018, 4- and 6-week-old seedlings were transplanted at four dates: March, April, May and June. In 2019, transplanting dates included April, May and June and seedling age was 5 weeks. In 2018, the March planting experienced severe frost during the initial field period resulting in crop failure. In 2017 and 2019, plants could withstand shorter and less severe frost events. Seedling age did not significantly affect tuber parameters. Transplanting in June resulted in lower marketable yield (> 28 mm) compared with earlier transplanting dates when crops were harvested in September. At full crop senescence, no differences in marketable yield were observed. The optimal transplanting window, taking into account weather-related risks, is approximately between early April and end May. For some genotypes, crop cycle length was observed to be a more important yield-determining factor than transplanting date.

Comparing annual and biennial crop cycle on the growth, yield and quality of saffron using three corm dimensions

Saffron (Crocus sativus L.) is a geophyte plant belonging to the Iridaceae family and it is appreciated for its red dried stigmas used as cooking spice and flavouring agent. Effects of crop cycle length and mother corm dimension, as well as their interaction, have been evaluated on the flowering (morphological traits of flowers, days to flowering, flowering interval and flower production), quantitative traits (stigma and daughter corm yield), vegetative development (leaf and daughter corm traits) and qualitative characteristics (coloring, bittering and aromatic powers) of spice. A two-year field study (2017–2019) was conducted to compare annual and biennial crop cycle of saffron using three corm dimensional classes (D1: 2.0–2.5 cm, D2: 2.6–3.5 cm and D3: 3.6–4.5 cm) according a split-plot design with 3 replications. The results showed that the corms of D3 class, planted in annual crop cycle, produced flowers with the highest stigma length (42.2 mm), and dry weight of stigmas (7.4 mg), stamens (11.4 mg) and tepals (40.7 mg). The highest number of flowers per m2 (311.8) and stigma yield (20.7 kg ha−1) were found when corms belonging to D2 class were planted in biennial crop cycle, meanwhile the highest daughter corms production (35.9 t ha−1) was obtained when corms belonged to D3 class were planted in annual crop cycle. Number of daughter corms per m2 with a horizontal diameter from 3.1 to 4.5 cm and weight from 10.1 to > 25 g decreased as increasing the crop cycle length. In biennial crop cycle, corms of D1 class produced more daughter corms belonged to 3.1–3.5 cm diameter class and to 15.1–20 g weight class compared to D2 and D3 classes. Regarding to the spice quality, coloring and bittering powers were positively influenced by biennial crop cycle. According to International Standardization Organization (ISO 3632) references, the maximum values of color (306.3 A1cm1% 440 nm) and taste (116.2 A1cm1% 257 nm) were reached in spice obtained from “biennial crop cycle x D2 class” interaction. No significant effect of all experimental factors on aromatic power was found. It was concluded that the evaluation of combination between crop cycle length and corm dimension is necessary in the saffron management in order to achieve the optimum yield of stigmas and corms, to improve the qualitative traits of spice and to enhance the by-products as corms of D1 class.

Changes in agronomic characteristics and galactomannan content in twenty cluster bean genotypes of different origins affected by sowing dates

Cluster bean guar or (Cyamopsis tetragonoloba L.) a valuable and multipurpose legume, due to its galactomannan and the seeds high in protein, is widely used in different industries. A field study was carried out using factorial experiment in a randomized complete block design with three replications to evaluate the influence of different sowing times (May 15, June 22, and July 27) on performance (seed yield, harvest index, biological yield, etc.), qualitative attributes (galactomannan, protein, carbohydrate, etc.), metabolic traits (lipid, pHenol, fiber, etc.) and yield components (branch/plant, pod/plant and plant height) of 20 guar genotypes (RGC-1066, BR-99, Sarbaz, HG-867, RGC-936, S-5488, S-5490, Dalgan, Iranshahr, Pishen, RGC-1038, RGC-1017, S-5498, RGC-1031, Saravan, S-5499, RGC-986, RGC-1003, HG-884 and HG-563) from three different origins (India, Iran and Pakistan). According to the ANOVA results, plant height, harvest index, the number of pod/plant, total chlorophyll, carbohydrate rate, gum content, and gum yield were significantly changed (p < 0.01) by sowing dates. Guar traits such as plant height, the length of crop cycle, number of pod/plant, harvest index, and protein yield were significantly (p < 0.01) impacted by a two-factor interaction (planting time × genotypes). Based on the results, RGC-1066 and Dalgan showed the maximum and minimum amount of seed yield, respectively. However, the maximum and minimum amount of protein was obtained from RGC-1003 and RGC-1038, respectively. July × HG-884 and July × HG-563 interactions showed the maximum amount of protein yield. The number of branch/plant, pod/plant, harvest index, gum content, and gum yield showed a positive significant correlation with seed yield. Regarding galactomannan and protein contents, HG-884 and RGC-1066 are suitable for gum extraction and guar meal, whereas HG-563 and RGC-1003 due to the high protein content are suitable for meal. RGC-1066 and Iranshahr exhibited the maximum amount of carbohydrate content. In addition, RGC-1066 and RGC-1038 exhibited the maximum amount of galactomannan and can be used for industrial applications.

Impact of Climate Change on the Growth of Typical Crops in Karst Areas: A Case Study of Guizhou Province

Climate change has emerged as a significant man-made global environmental challenge marked by rising temperature. The global rising temperature is supposed to alter climatic patterns like floods and droughts, thereby affecting human life supporting system and global food production. In order to clarify the impact of weather events on agricultural production in karst landforms, this study selected the indices of the growth period of crops (start time and duration), growing season precipitation, intense precipitation, number of consecutive rainless days, and number of drought-flood abrupt alternation events to evaluate the variation trend of future weather events and their impact on crop growth in Guizhou Province, China. The results show that (1) the climate is generally getting warmer. From 2019 to 2050, the sowing period of winter wheat and rice tends to be postponed. The duration of maize and rice’s growth period will be shortened, and the life cycle of wheat also emerges as having a decreasing tendency except for those from the southern region. Comparing with the mean value during 1961 to 2018, the average crop cycle length of winter wheat, summer maize, and rice was shortened. The rate of shortening of crop cycle length is faster than the value during 1961 to 2018. (2) In the next 30 years, extreme precipitation concentrates in June and mainly falls in the central and southeast parts of Guizhou Province. In addition, summer is the outbreak period of drought events and drought-flood abrupt alternation events, which has a great impact on crop’s growth. This study can provide references for the planting system, structure, layout, and management of crops in the karst region.

From sunlight to seed: Assessing limits to solar radiation capture and conversion in agro-ecosystems

Yield depends upon the amount of photosynthetically active radiation (PAR) absorbed by the crop during the growing season and its conversion into harvestable biomass. Little is known about attainable and actual efficiencies involved in absorbing incident PAR (ea) and converting it into yield (ec) in producer fields. We developed a novel approach consisting of producer data, satellite imagery, and crop modelling to assess ea and ec in agro-ecosystems. Simulated phenology and satellite imagery were used to estimate incident (IPAR) and absorbed (APAR) PAR during the crop season for 3096 soybean fields sown across the US North Central region during 2014–2016. Quantile regression was used to derive upper limits for ea and ec and multiple-regression analysis was performed to identify biophysical drivers of the observed variation in these two efficiencies. Differences in weather, soil, and management resulted in a wide range in crop cycle length (58–126 d), total IPAR (580–1250 MJ m−2), and seed yield (0.8–6.3 Mg ha−1). The relationship between yield and total APAR was curvilinear, indicating marginal yield gains in the upper APAR range. Attainable ea represented 65% of total IPAR, while attainable ec ranged from 0.6 to 1.2 g seed MJ−1 depending upon total APAR. Average producer ea and ec were 14 and 29% below their attainable efficiencies. Average efficiency in converting IPAR into yield was 0.8%, with an upper limit of 1.1% derived from the 95th percentile of the field data distribution. Although weak, relationships between efficiencies and meteorological factors such as IPAR, temperature, water balance, and diffuse radiation were consistent with previous literature. There was a strong trade-off between ec and ea indicating that maximizing both efficiencies simultaneously was not possible in producer fields. Our approach can be used to determine attainable and actual efficiencies in capturing and converting radiation into yield, set realistic yield limits, and understand relationships between producer yield and management practices.

Management and spatial resolution effects on yield and water balance at regional scale in crop models

Due to the more frequent use of crop models at regional and national scale, the effects of spatial data input resolution have gained increased attention. However, little is known about the influence of variability in crop management on model outputs. A constant and uniform crop management is often considered over the simulated area and period. This study determines the influence of crop management adapted to climatic conditions and input data resolution on regional-scale outputs of crop models. For this purpose, winter wheat and maize were simulated over 30 years with spatially and temporally uniform management or adaptive management for North Rhine-Westphalia (˜34 083 km²), Germany. Adaptive management to local climatic conditions was used for 1) sowing date, 2) N fertilization dates, 3) N amounts, and 4) crop cycle length. Therefore, the models were applied with four different management sets for each crop. Input data for climate, soil and management were selected at five resolutions, from 1 × 1 km to 100 × 100 km grid size. Overall, 11 crop models were used to predict regional mean crop yield, actual evapotranspiration, and drainage. Adaptive management had little effect (<10% difference) on the 30-year mean of the three output variables for most models and did not depend on soil, climate, and management resolution. Nevertheless, the effect was substantial for certain models, up to 31% on yield, 27% on evapotranspiration, and 12% on drainage compared to the uniform management reference. In general, effects were stronger on yield than on evapotranspiration and drainage, which had little sensitivity to changes in management. Scaling effects were generally lower than management effects on yield and evapotranspiration as opposed to drainage. Despite this trend, sensitivity to management and scaling varied greatly among the models. At the annual scale, effects were stronger in certain years, particularly the management effect on yield. These results imply that depending on the model, the representation of management should be carefully chosen, particularly when simulating yields and for predictions on annual scale.

Maize yield under a changing climate in the Brazilian Northeast: Impacts and adaptation

This paper assessed the potential impacts of climate change on maize productivity in the Brazilian Northeast. To achieve this objective, bias-corrected regional downscaled scenarios from three global models for the representative emission pathways, RCP4.5 and RCP8.5, for the periods 1980–2005, 2007–2040, 2041–2070, and 2071–2099 were used as input data for a crop productivity model. Because increased temperatures are likely to shorten the crop cycle length, thus reducing productivity, we investigated the lengthening of the growing cycle as an adaptation strategy. To cope with the reduction of rainfall projected by future climate scenarios, we analyzed the potential impact of irrigation on productivity. The results showed that climate change effects would be mostly negative for maize rainfed agriculture, particularly for the worst-case scenario (RCP8.5, 2071–2099), in which losses were expected to reach more than 60%. However, productivity losses were limited to a maximum of 30% for all RCP4.5 scenarios and before 2070 for the RCP8.5 scenario. The use of maize cultivars with a longer crop cycle for rainfed agriculture was likely to increase the average productivity in all scenarios, although it came at the expense of increasing the risk of crop failure. Regarding the use of irrigation, there was an improvement in productivity for both the short- and long-cycle cultivars, although longer crop cycle cultivars had a decisive advantage, with a drop in yield of less than 20% for all RCP4.5 scenarios and for the RCP8.5 scenario until 2070 compared to the present climate. We estimated the total production and the increase in water demand based on the existing and projected irrigated areas in the region and concluded that it is possible to avoid significant losses in total maize production in the region for all scenarios, with the exception of the 2071–2099 RCP8.5 scenario. However, sustaining such levels of production requires a significant increase in water consumption (up to 140%).

Assessing the influence of row spacing on soybean yield using experimental and producer survey data

Narrowing row width in soybean fields leads to earlier canopy closure, which may increase capture of incoming solar radiation during critical crop stages for yield determination. Theoretically, this should enhance seed yield. However, in prior studies, the impact of narrowing row spacing on soybean yield has been inconsistent. To explore on a broader scale the potential factors underlying this inconsistency, we evaluated the yield difference between narrow (NR; ≈38 cm) and wide (WR; ≈76 cm) row spacing using two sources of yield and management information: (i) data collected from 4879 soybean production fields via a multi-year, multi-state survey of soybean producers in the North Central US region; and (ii) data extracted from 129 site-year experiments that quantified NR-WR yield difference. The producer fields were allocated to their respective climate-soil domains to enable analysis of the NR-WR yield difference within each domain. The experimental trial data originated from three US geographic regions: south, central, and north. Key crop developmental stages in each trial were estimated using a soybean crop simulation model to discern if changes in crop phenology or any weather variable occurring before versus after a specific crop stage modulated the magnitude of the NR-WR yield difference. Analysis of experimental trial data indicated that, while NR yields were overall higher than WR yields, the NR-WR yield difference varied by region: 540 (south), 104 (central), and 240 kg ha−1 (north); the respective NR yields were greater than WR yields in 92%, 68%, and 84% of the cases. In the north and south regions, the NR-WR yield difference increased when the crop cycle length decreased as a consequence of later sowing date, earlier cultivar maturity group, and/or higher temperature. The relatively smaller (and occasionally negative) NR-WR yield difference detected in the central region was likely the result of environmental conditions that favored canopy closure irrespective of row spacing. In contrast to the analysis of the experimental database, no consistent NR-WR yield differences were detected in the producer field database. We hypothesize that the apparent absence of a significant NR-WR effect in the producer dataset is likely associated with the background management used with narrow spacing, together with yield losses due to wheel damage and greater disease pressure. This complementary approach using both producer and experimental data can help evaluate if practices documented in experimental trials to enhance yield realize equivalent yield increases in producer fields and, if not, explore underlying causes for the discrepancy.

Morphological, biological, productive and qualitative characterization of 68 guar (Cyamopsis tetragonoloba (L.) Taub.) genotypes

Guar (Cyamopsis tetragonoloba (L.) Taub.) is a valuable industrial crop, widely cultivated in India and Pakistan for the high galactomannan content of its endosperm. The present multi-trait characterization of 68 guar genotypes was conducted to identify an ideotype combining desirable traits suitable for cultivation in a Mediterranean climate and that allows an easy harvest. Plant height, branch number, stem diameter, length of crop cycle, number of cluster, number of pods per plant, number of seeds per pod, 1000 seeds weight, seed production per plant, galactomannan and protein content were measured. In addition, correlations between morphological and productive traits were applied, calculating the relationships between traits, and giving biological meaning to the ideotype. To select high performance genotypes under Mediterranean climate, we mainly took into consideration non-branching (easy harvestability, uniformity of maturation) and short crop cycle genotypes with valuable productive and qualitative traits. From this viewpoint, the results showed that 17 genotypes resulted non-branching, 11 genotypes showed a short crop cycle and seven genotypes were characterized by a seed production greater than 50 g plant−1. Four of the 17 genotypes (PI 288757, PI 340263, NC70300525and PI 288745) possess all these desirable traits along with good seed production and therefore should be selected as multi-trait high performance genotypes. As far as the galactomannan and protein contents are concerned, a lower coefficient of variation emerged when compared to those of the morphological or productive traits. Correlation analysis showed that plant production was related to cluster number, number of pods per plant, seeds per pod, number of branches and length of crop cycle. Finally, an interesting negative association between galactomannan and protein content was found.

Assessing future meteorological stresses for grain maize in France

Recent climate change has already affected maize cropping in France allowing for example earlier sowing dates in southern France and the growth of early season varieties in northern parts of the country. The climate will continue to evolve as discussed in all IPCC reports and there is a need for farmers, seed companies and agricultural cooperative corporations to be able to anticipate those changes. The ambition of our work is to provide them with the means to get ready to adapt by analyzing a) the time evolution of meteorological stresses and certain management practices throughout the crop's growth cycle, b) the impacts of climate-induced changes in calculated sowing dates on those stresses and practices. We have applied the method we developed in a former paper to study the climatic suitability of maize in two contrasted areas of France, Ile-de-France in the North and Midi-Pyrénées in the South. Three climate change scenarios, two climate models and two maize varieties distinct in terms of precocity were used to try and ensure meaningful results. Whatever the scenario, model and variety, maize will be sown earlier than it is currently the case in both regions, especially in Midi-Pyrénées. Whatever the sowing date, rising temperatures in the future will be favorable for late varieties in the current cooler areas, and therefore even farmers in Ile-de-France will be able to grow varieties with a wide range of crop cycle length. However heat and water stress will increase in both regions between flowering and maturity, irrespective of the sowing date and scenario, thereby limiting the possibility to achieve potential yields. In Midi-Pyrénées compromises will need to be found between early sowing to minimize some later stress and increasing risks of frost during emergence, that do not currently exist.

Irrigation Water Effect In Soybean Crop In Uruguay

In the last 10 years, soybean crop area has increased strongly, being 309x103 ha in 2005 to over 106 ha in 2015. Uruguayan climate conditions allow the soybean sowing between October to December according to crop cycle, and its cycle is completed between March to April. However, the irregular rainfall throughout the crop cycle causes short periods droughts that may trigger an important yield decrease, depending on the stage crop. The supplemental irrigation allows to reduce the water deficit in particular crop periods, given to farmer a high and stability yield. The need to have a good farm irrigation strategy according to the different soybean cycle length is the main reason for soybean yield response studies under supplemental irrigation. The experiment was conducted at Salto (Northwest of Uruguay) during 2013-2014 crop season. Four soybean crop length cultivars (4990, 5500, 6.2i, 8000) were used. Two treatments were applied, rainfed and irrigation, with three replications randomized block design. Irrigation treatment received the 100% of maximum crop evapotranspiration according to FAO56. Crop cycle length was 140 days with a total rainfall of 575 mm. Sprinkler irrigation system was used with an average rainfall of 6.6 mm hour-1. The average water depth was 232 mm distributed in 7 irrigation events between December and January. Regardless of crop cycle, irrigation treatment showed a higher yield than rainfed treatment (differences about 80%). Long cycles soybean cultivars, irrespective of the irrigation treatments, reached a higher yield than the shorter ones (differences over 50% and 20% in rainfed and irrigation treatments, respectively). Therefore, in the North of Uruguay, soybean crop with long cycle, and under supplemental irrigation, should allow a greater yield to the farmers with the aim to reach a high profit margin.

Potential Yield of Contrasting Soybean Maturity Groups in Southern Uruguayan Conditions

Soybean potential yield (Glycine max (L.) Merr.) is determined by temperature, radiation, photoperiod and genotype in every location. The variability of potential yields is strongly associated with changes in available solar radiation through years. Selection of management practices that lead to maintaining high yields are: genotype, sowing date and row spacing. Sowing date enables coupling solar radiation offer with the crop stages were yield is defined. Furthermore, potential yield for every environment depends on genotype. Selection of the maturity group (MG) defines the initiation of the reproductive period, which conditions the nod number, the maximum leaf area index (LAI) and the environmental conditions during grain filling. Additionally, growth habit of each genotype is also related to potential yield. Early sowing date allows the expression of the greatest differences among MG. A crop growth simulation study showed that the average potential productivity of early maturing cultivars (MG from III to V) achieved higher yields than later maturing cultivars (MG from V to VII) at early sowing date conditions in Uruguayan latitudes. Later maturing cultivars localize their critical period when daily radiation curve declines (late January - February) and consequently the growth rate during reproductive stage is not maximized. The objective of this study was to determine the potential crop growth and yield of different MG in two ambient crated by early and mid sowing date, at southern Uruguayan latitudes. The experiment was carried out during summer 2014-2015. Contrasting MG -from III to VII-were tested on two sowing dates: 15/10 and 15/11. Different growing variables were measured during the growing season: evolution of the intercepted solar radiation, biomass (B), soil water content, number of pods per square meter and crop yield. Results showed that early maturing cultivars expressed higher yields in both sowing dates. The yield on mid-October sowing date ranged from 5400 to 6300 kg ha-1 for early maturing cultivars and 4600 to 5600 kg ha-1 for later maturing cultivars. For mid November sowing date the yields ranged from 4600 to 5200 kg ha-1 for early maturing cultivars and 3800 to 5500 kg ha-1 for later maturing cultivars. However, evolution of LAI and B was similar among MG. The main difference showed was accumulated biomass at initial reproductive stage. Daily water uptake did not differ among MG; nevertheless, total water uptake responded positively to the increase of the crop cycle length. The highest potential yield for season 2014-2015 was reached with early maturing cultivars. Results showed that yields could be maximized with management practices as supplementary irrigation and the use of short MG sowed in October. The use of these practices lead to obtain over 6000 kg ha-1 crop yield combined with high water productivity.

Determinación de las etapas de inicio de macollamiento, inicio de primordio, floración y madurez en la planta de arroz, con el sistema S, V y R correlacionado con la sumatoria térmica

En el cultivo del arroz, la temperatura es uno de los factores de clima que ejerce mayor efecto sobre el crecimiento, desarrollo y producción de la planta; la acumulación de calor constituye la energía necesaria para completar un determinado estado fenológico. Se determinó en plantas de arroz las etapas de inicio de macollamiento, inicio de primordio, floración y madurez de cosecha, empleando el sistema S, V y R, propuesto recientemente por Counce et ál. (2000), que consiste en el conteo del número de hojas completamente desarrolladas; además, se correlacionó con los grados día acumulados que la planta presentaba en ese momento, para estimar con cuántos grados día se iniciaba una etapa fenológica; este parámetro está relacionado con la temperatura promedio diaria y una temperatura base de 10ºC. Para el inicio de macollamiento la planta necesitó de 140,9 grados día; en inicio de primordio 1268,9; para floración 1746,0; y completó su ciclo con un total de 2333,2 grados día. El estudio permite concluir que, para una variedad de ciclo largo (130-135 días), cuando la acumulación de grados día sea igual o similar a los datos anteriores, la planta está iniciando una de las etapas fenológicas mencionadas; no obstante, se debe calibrar cada una de las variedades de mayor uso por el productor, debido a que entre ellas existen diferencias en duración del ciclo de cultivo.

SOWING WINDOWS FOR A SPRING CROP INTRODUCED IN RICE CULTIVATION AREAS AFFECTED BY LOW TEMPERATURE AND RADIATION

SUMMARYIn mountainous areas of Continental South East Asia, double cropping in the irrigable valleys and terraces is often promoted as a way to increase farmers’ income while alleviating the pressure of agriculture on fragile slopes. However, cold temperature and low global radiation may constrain this strategy. Lethally cold events may occur, and increases in crop cycle length may jeopardize the correct timing of the main rice crop, taking place in summer. The model PYE (potential yield estimator) simulating the impact of temperature and radiation on the development and yield of annual crops was adapted to account for the range of temperature occurring in the area under study. It was calibrated against experimental data for the three crops that are most often considered as spring crops in the irrigable land of the northern mountains of Vietnam: rice, soybean and maize. Then a virtual experiment was designed in order to simulate various scenarios combining crop species and sowing date with climatic data accounting for variability of climate across years, location and elevation. Completed with a sensitivity analysis, it allowed to define favourable ‘sowing windows’ for non-water limited environments, based on the three following criteria: high average yield, low incidence over years of lethally cold events and low incidence over years of delays in the maturity of the spring crop. The length of this sowing window varied greatly across the scenarios tested. The widest was obtained for the case of soybean whatever the location and elevation, which makes it the less risky of the tested options. The approach followed proved effective to identify favourable and unfavourable environments in order to help better targeting the policy in support to the introduction of a spring crop in the mountains of Vietnam.

Nitrate leaching from forage legume crops and residual effect on Italian ryegrass

Forage legumes can improve the N-efficiency of crop systems but also increase environmental pollution. This research investigated the NO3-N leached during the growth cycle of four forage legume crops and of barley and evaluated their residual effect on yield, N uptake and nitrate leaching of Italian ryegrass. For all crops, the nitrate leaching losses concentrated in the four months after seeding and accounted for over 78% of total N leached. On a yearly basis, nitrate leaching from legumes increased with the decrease in crop cycle length from 18 (alfalfa) to 47 kg N ha -1 (field bean). All legumes had a significant residual effect on forage and N yield of Italian ryegrass. In terms of both forage yield and nitrogen content, the beneficial effects of preceding legume crops ranked in the order: alfalfa > red clover = sulla > field bean, and was higher for N content than for dry matter.

Irrigation Water Effect In Soybean Crop In Uruguay

In the last 10 years, soybean crop area has increased strongly, being 309x103 ha in 2005 to over 106 ha in 2015. Uruguayan climate conditions allow the soybean sowing between October to December according to crop cycle, and its cycle is completed between March to April. However, the irregular rainfall throughout the crop cycle causes short periods droughts that may trigger an important yield decrease, depending on the stage crop. The supplemental irrigation allows to reduce the water deficit in particular crop periods, given to farmer a high and stability yield. The need to have a good farm irrigation strategy according to the different soybean cycle length is the main reason for soybean yield response studies under supplemental irrigation. The experiment was conducted at Salto (Northwest of Uruguay) during 2013-2014 crop season. Four soybean crop length cultivars (4990, 5500, 6.2i, 8000) were used. Two treatments were applied, rainfed and irrigation, with three replications randomized block design. Irrigation treatment received the 100% of maximum crop evapotranspiration according to FAO56. Crop cycle length was 140 days with a total rainfall of 575 mm. Sprinkler irrigation system was used with an average rainfall of 6.6 mm hour-1. The average water depth was 232 mm distributed in 7 irrigation events between December and January. Regardless of crop cycle, irrigation treatment showed a higher yield than rainfed treatment (differences about 80%). Long cycles soybean cultivars, irrespective of the irrigation treatments, reached a higher yield than the shorter ones (differences over 50% and 20% in rainfed and irrigation treatments, respectively). Therefore, in the North of Uruguay, soybean crop with long cycle, and under supplemental irrigation, should allow a greater yield to the farmers with the aim to reach a high profit margin.

Determination of maize crop coefficients in humid climate regime using the eddy covariance technique

Italy is one of the most important maize producers in the EU, and the Po Valley plain in northern Italy is the largest maize area in the country, with over 1millionha planted. Water consumption for maize is very high because the crop covers almost 30% of the agricultural land of the plain and is irrigated mainly by border irrigation. Conversion to more efficient methods is currently under discussion for many areas. Whatever the irrigation method adopted, an accurate knowledge of maize irrigation requirements is essential to improving irrigation scheduling and water use planning on a regional scale. The FAO-56 “single crop coefficient” procedure is currently the most widely used procedure for the estimation of crop irrigation requirements. However, in the last 15 years, many authors have shown that FAO-56 crop coefficients, even if adjusted to account for local conditions (climate, soil, irrigation and crop management), may differ by up to ±40% from experimentally determined values. In this study, Kc was derived as the ratio of the actual crop evapotranspiration in well-watered conditions (ETc), as measured by the eddy covariance technique at two maize fields over three years, to the reference crop evapotranspiration ETo. The crop cycle length ranged from 136 to 146 days, depending on the year and the harvesting date, and the accumulated growing degrees-days (GDD) varied from 1590 to 1730°C for silage and grain maize, respectively. The average locally developed Kc values for initial, middle and late growing seasons were 0.33, 0.99 and 0.89–0.35 (the Kc-end value depends on the harvesting time). The experimental Kc-mid was 15% lower than the FAO-56 value adjusted for local conditions. Average seasonal ETc values were 430 and 400mm for grain and silage second-crop maize, respectively