Research on the morphology, biology, productivity and yields quality of the Amaranthus cruentus L. in the southern part of Romania

Currently, according to the specialists in the field, Amaranthus species are part of alternative agricultural crops recommended for organic farming. In this context, our scientific approach is to analyse the adaptability of these species in the specific conditions of the southern part of Romania (Reviga village, Ialomita County). Thus, for two consecutive years, two varieties of Amaranthus cruentus, namely ‘Bolivia 153’ and ‘Golden Giant’, were studied regarding: morphology, biology, cultivation technology, plant productivity and quality of yields in the organic farming conditions. After the study period, the ‘Golden Giant’ variety was characterized by the following: 8 days sowing-emergence period; flowering start on 21 July; 124 days vegetation period; 839.3 Growing Degree Days (GDD) (Σ t °C > 15 °C); 23.24 g grains mass per plant; 1.375 g Thousand Weight Grains (TWG); 2,647 kg ha grains yields. By comparison, ‘Bolivia 153’ variety plants were presented as follows: 11 days sowing-emergence period; flowering start on 21 July; 127 days vegetation period; 842.4 GDD; 22.09 g grains mass per plant; 1.46 g TWG; 23.78 kg ha grains yields. In average, the chemical composition of Amaranthus cruentus grains was: 15.20% proteins; 51.70% starch; 5.96% lipids; 13.36% cellulose and 3.35% ash. In conclusion, the experimentation area proved to be favourable to Amaranthus cruentus cultivation, so that the tested varieties behaved well, had a fairly uniform emergences, and the good level of grains yields and quality.


Introduction
The economic, social and political evolution of human society in the last decades has brought to the fore the question of natural resources, scientists increasingly asking the extent to which these resources will be able to support economic development in the future and will provide food for a growing population, and will contribute to the eradication of underdevelopment (FAO, 2017). The accentuation of major socio-economic phenomena (demographic explosion, tendency of natural resources depletion, deterioration of the quality of the environment, pollution), have led to search and to find the alternative solutions for a sustainable perspective of the environment and biodiversity (Haros and Schoenlechner, 2017). In this context, the organic farming system is also included, as an alternative system of agricultural production, which respects the environment, biodiversity and natural resources. Also, alternative crops promoted by organic farming system are based on these principles and represent an alternative of the plant species commonly cultivated by farmers. An alternative crop could be defined as an agronomic crop not usually grown in a geographic reason, selected for use due to potential high sale value or specialized benefit to the farming system (Isleib, 2012). A crop can be very common in one geographic area and considered an alternative in another (Isleib, 2012). Crop diversity is a key tenet of organic agriculture. Having multiple crops that fill distinct niches in an agroecosystem improves the ability to manage weeds, diseases and insect pests as well as potentially improving the environmental performance of the cropping system (Duwayri, 2001). Research can help overcome production and market obstacles that enable the successful introduction of alternative crops (FAO, 2017). Risk reduction through diversification (related to climatic and biotic vagaries, particularly in fragile ecosystems and commodity fluctuations) by expanding locally adapted or introducing novel varieties and related production systems, will contribute to improved food security and income generation for resource poor farmers and protect the environment (Duwayri, 2001). In this sense, Amaranthus species with Chenopodium quinoa, represented the most popular alternative crop species. These species have the centres of origin in South America and were brought in Europe by the Spanish conquistadors, as an ornamental plant (16th century). Until the sec. XIX the Amaranthus species were used as an ornamental plant, but also for the consumption of green leaves, in most areas with tropical climate, and in Africa it became an important vegetable (Cole, 1979). Amaranth is a crop with high potential for economic exploitation similar to maize, wheat, sorghum, barley, rice, and soybean (Innovation NRCACT, 1984;Rastogi and Shukla, 2013;Akin-Idowu, 2017). Amaranth has an excellent nutritional value and high genetic and phenotypic diversity. Their valuable nutritional content, their adaptability to harsh environments, their diversity of uses, and the food culture and traditions associated with these grains, are at the basis of their extensive use in the Andes over centuries (Giuliani et al., 2012). Amaranthus species have different uses: mixtures of cereals for bread or for breakfast, crêpes, pastries, cakes, as raw material in the industry (syrups, diet products, starch, and oil), salads. They can be used as an excellent feed for animals, but also as medicinal plants, in digestive disorders or as a disinfectant (Toader and Roman, 2011).
Amaranthus species is considered to potentially offer an alternative crop in temperate and tropical climate (Das, 2016). In recent decades, amaranth grain has been extensively studied for its remarkable nutritional profile and agricultural characteristics, e.g., having a short cultivation period and being drought resistance (Najdi Hejazi et al., 2016). Introduction of amaranth as a human food has been slow, but today it is produced and used as a grain or leafy vegetable in India, China, Southeast Asia, Mexico, the Andean highlands in South America and the United States (Robert, 1996). The Nebraska panhandle has become the most concentrated area of production of grain amaranth in the US (Rani, 2017). This statement is supported because the crop is easy to cultivate and is not pretentious with the cultivation conditions, it can also be used as a flour for obtaining pasta, but also for extracting lysine and tryptophan, starch, oil squalane, substances needed for the drug or cosmetics industry (Alvarez-Jubete et al., 2010). The leaves can be consumed as a soup, but also for the extraction of proteins, dyes or inflorescences can be used for various decorations (Toader and Roman, 2011). Amaranthus grains have a high nutritional value due to the presence, in a large quantity, of important biochemical compounds for human nutrition and health (Nadathur, 2016). Most of the biochemical components (proteins, lipids, minerals, vitamins), are present in greater quantity, compared to other species (Nadathur, 2016). Orona-Tomayo and Paredes-Lopez, in 2017, reported that, for the different Amaranthus species, proteins can reach up to 19.3%, even 20%; the richness of the essential amino acids was also highlighted: 5-7% lysine (g 100 -1 g protein), 3-4% tryptophan, 3-4% leucine, which gives it a high nutritional value compared to the conventional cereals (Orona-Tamayo and Paredes-Lopez, 2017).
Information about the phenological growth stages of crops is fundamental and useful to agriculture. These researches can provide valuable data for the planning, organization and timely execution of certain agricultural activities such as those of prevention and protection that require detailed information on the specific vegetation phases of a crop (the appearance of the inflorescences, the flowering, the stages of maturity, etc.). These data can be used in mathematical modelling, which can predict the timing of phenological events according to certain conditions: temperature, precipitation, duration of sun shine, etc (Tonnang et al., 2018, Erten et al., 2014. However, details about the growth and development of amaranth is fundamental to its cultivation, but reports on the phenological growth stages, development, and the life cycle of amaranth are limited (Martínez-Núñeza et al., 2019;Artemyeva et al., 2019). The importance of this research derives from the improve knowledge about ecology, biology and productivity of Amaranthus cruentus in South part of Romania, also about possibility to introduce of this plant in crops rotation system of organic farming.

Experimental design
The research was organized with the purpose of studying the morphology, biology, productivity and yields quality of Amaranthus cruentus species, respectively, two varieties, 'Bolivia 153' and 'Golden Giant',in terms of adaptability to the organic farming conditions of Romanian, in 2017-2018 period.
The experimental field belongs to a farm in Reviga village (44°41'34''N 27°06'26''E) (Ialomita County), in South part of Romania. The sites were managed according to organic agriculture guidelines (EC 834/2007 andEC 889/2008). The farm soil was analysed by Ialomita County Office of Pedological and Agrochemistry Studies. The pH of soil was weakly acidic oscillating between 6.1-6.5, in average 6.3. Total soluble salts for the analysed samples indicate soil without salinization problems (non-saline soils, with values <0.100%). Mineral nitrogen represents the amount of soil content in changeable and accessible form nitric and ammoniacal nitrogen. The results indicate normal soil supply in mineral N (8.4 g 100 g -1 of soil). The supply in Kalium (K) (potentially assimilable) extractable in Aluminium of the soil is very good for the analysed samples (> 200 K ppm). Content in humus was medium supplied for the analysed soil (2.1-4.0% humus).
The biological material for sowing came from Germany, certified by the inspection and certification body for organic agriculture system. The previous crops were peas (Pisum sativum, pulses crops category) to benefit from the nitrogen fixed by this plant. No other fertilizer was applied. The soil tillage consisted in a disking after the harvesting of the previous crop and the release of vegetal debris, followed by the plowing at 25-30 cm depth. In the spring, the field was disked, followed by the preparation of the germinal bed with the combiner, at a depth of 6-8 cm.
The sowing was done by hand, in 20 of April for both years, at a depth of 1-2 cm. The area of the plot was 5 m-2 (2.5 m long, 2 m wide). The experiment was organised by Randomized Block Design Method, in four replications. The density was 100,000 grains ha -1 , with 50 cm between plants rows. During on the vegetation period the weed control was executed manually. Other pest or diseases not observed. The harvesting was made manually.

Collecting data, measurements and methods
During the vegetation period until harvesting, phenological observations and biometric measurements of Amaranthus plants were made on the dynamics (at each 8-10 days). Determinations concerned: emergence date, plants height, nodes of stem, leaves formation and their number, Leaf Area Index, appearance data of inflorescence, flowering, maturity and crop density.
Growing Degree Days (GDD) has been used to calculate the durations and thermal requirements for each phenophase. "To calculate the daily thermal units, the equation of Gilmore and Rogers (1958) was used (GGD = [(Tmax + Tmin) 2 -1 ]− Tb), where Tmax-Tmin are daily maximum and minimum air temperatures, respectively, Tb is the base temperature, evaluated at 15 °C (Gilmore and Rogers, 1958)". The maximum and minimum daily temperatures were obtained from Ialomita weather station. The average multiannual temperature was 10.5 °C, with 1.0 °C higher than Romania's average multiannual temperature of 9.5 °C. The hottest month of the years was July, with a monthly average of 22.1 °C, followed by August with 21.1 °C, and the coldest was January with -3.0 °C. Separately by years it is found that in the years of experimentation, the temperatures have registered great differences in comparison with the multiannual monthly averages. Thus, for the year 2017-2018, the values of the average monthly temperature were recorded with 2.0-6.5 °C higher than the multiannual average. The warmest month was June, with the average temperature higher by 6.5 °C than the multiannual average; at a slight difference were the temperatures in July, with 5.7 °C and August, with 4.5 °C (Figure 1). For the second year of the research (2018) the annual amount of rainfall was 561.3 mm, slightly higher than the multiannual average of 556.1 mm. In this agricultural year the richest precipitations were recorded in May (73.4 mm), more with 5.7 mm, followed by December (72.6 mm), with 35.9 mm more than the average, multiannual monthly. The amount of precipitation in October, November and December was 172 mm, compared to 113.1 mm, which was the multiannual average. The smallest quantities were registered in February (24.8 mm) with a deficit of 7.3 mm compared to the multiannual average and September (24.7 mm), with a minus of 8.9 mm (Figure 2). 10 plants from each plot were used for determinations of productivity elements in laboratory. Have been eliminated the marginal plants to avoid the possible errors. After manually harvesting, in laboratory was made the number and quantity of grains per plants and TWG. For the TWG determination was used the standard method with 2 repetitions of 500 pure seeds.
Chemical analyses of grains were performed in Yields Quality Laboratory of Crop Science Department, Faculty of Agriculture, University of Agronomic Sciences and Veterinary Medicine of Bucharest. The equipment was a spectrophotometer (Instalab 600) calibrated by a company from Novisad (Serbia) to determine the content of dry matter, crude protein, starch, lipids, cellulose and ash. The Instalab 600 uses Near Infrared (NIR) technology and a statistical math treatment to predict the percent of constituent concentration within a sample.

Statistical procedures
Data presentation was done by processing the media for replications and for years. Significant statistical differences were determined by the Fisher's least significant differences (LSD) test and also the Student Neuman Keuls (SNK) test with the ARM 8.5 program.

Dynamics of plants height
From the analysis of the data contained in Table 1,  In terms of the dynamics of plant growth in height, some differences between varieties were found. Further, until maturity, the growth was 22.9 cm, with an average rate of 0.54 cm day -1 in the case of the 'Bolivia 153' variety, and 18 cm, with an average rate of 0.43 cm day -1 , in the case of the 'Golden Giant' variety.

Dynamics of nodes formation
The formation of nodes at 'Bolivia 153' variety took place during 71 days of vegetation, in which 12 nodes of stem were formed, with an average rhythm of 5.91 days node -1 . The first node was observed after 11 days from emergence, when 7.9 GDD were accumulated, and the intervals between the formation of nodes 2 and 5 were on average 7 days node -1 , with an average consumption of 28.37 GDD node -1 . In parallel with the intense increase in height of the stem, the rate of node formation also became more alert, so that the following 5 nodes at intervals of 3.6 days node -1 , with an average thermal consumption of 27.46 GDD node -1 . Node formation continued for another 14 days, resulting 2 nodes, at an interval of 7 days node -1 and with an average heat consumption of 69.9 GDD node -1 (Table 2).

Dynamics of leaves formation
The dynamics of leaves formation is presented in Table 3.
The plants of the 'Golden Giant' variety formed during 75 days of vegetation and after a thermal consumption of 452.6 GDD, 13 nodes, with an average rhythm of 5.76 days node -1 .
The formation of the first node, for 'Golden Giant' variety, was noted 13 days after emergence, after a thermal consumption of 14.1 GDD, and the following 4 nodes were formed within a period of 25 days, with an average rhythm of 6.25 days node -1 and an average consumption of 28.62 GDD node -1 . The formation of nodes 6-9 was staggered over 12 days, the average rhythm being 3 days node -1 and the thermal consumption of 12.6 GDD node -1 . The process of node formation continued for another 20 days, resulting 4 nodes, with an average rhythm of 5 days node -1 . In the case of the 'Bolivia 153' variety, the leaves formation (36 leaves in total) was carried out over a period of 92 days of vegetation, in which the thermal accumulation was 568.3 GDD; the average rate was 2.55 days leaf -1 and the average heat consumption was 15.68 GDD leaf -1 . On May 12, after 11 days from emergence, Amaranthus plants belong to the 'Bolivia 153' variety had 2 leaves, with a leaves area of 1.1 cm-2 plant -1 ; after 29 days, the number of leaves reached 11 leaves, with an area of 529.3 cm-2 plant -1 , resulting in an average rate of 2.63 days leaf -1 and an average consumption of 12.42 GDD leaf -1 . There were 29 days when the rate of leaf development was more alert. In this interval, 19 leaves were formed, with an average rate of 1.52 days leaf -1 and a thermal consumption of 13.8 GDD leaf -1 ; at the end of this interval, the Leaf Area Index was 2543.7 cm-2 plant -1 . The maximum value of the leaves surface, of 3,401.6 cm-2 plant -1 , was reached 21 days later, when the plants had a total of 36 leaves (Table 3).  Regarding the dynamics of leaves formation for the 'Golden Giant' variety, it can be emphasized that the more alert rate was noticed during the period June 10-July 16, in which 23 leaves were formed. In this interval the sum of the useful temperatures was 319 GDD, resulting an average of 1.60 days leaf -1 formation rate and a consumption of 13.86 GDD leaf -1 . On May 12 (after 8 days after emergence) the Leaf Area Index was 0.9 cm-2 plant -1 , then, as the vegetation advanced, the leaf area evolved upwards, so that on June 3 or after the accumulation of 101.1 GDD the leaf surface reached 115.9 cm-2 plant -1 ; a month later, on July 1, a leaf area of 2,034.6 cm-2 plant -1 was determined, and a maximum leaf area of 3,357.7 cm-2 plant -1 was reached on August 7, after accumulating 640.7 GDD.

Dynamics of inflorescence formation, flowering and grains formation
Under the conditions of 2017 year, the inflorescence appeared on the 'Bolivia 153' variety plants after 56 days after emergence or 248.3 GDD accumulations, while on the 'Golden Giant' variety plants, the beginning of the inflorescence formation was noted after 58 days after the emergence, and a thermal accumulation of 291.2 GDD. The beginning of flower opening was started after 22 of days for 'Bolivia 153' variety and 23 days for 'Golden Giant' variety. The maturity stages developed during 35 of days for ''Bolivia 153' variety and 9 days faster for the 'Golden Giant' maturity. The full maturity means 842.4 GDD of 'Bolivia 153' variety and 839.3 GDD of 'Golden Giant' variety (Table 5).

Productivity elements and grains yields
Following the analysis of the productivity elements, the 'Bolivia 153' variety has a number of 13,660 grains per plant, with a mass of 18.23 g plant -1 ; 15,876 grains plant -1 were determined at the 'Golden Giant' variety, their grains mass being 21.75 g plant -1 , in 2017. In 2018, the values were superior at all indexes. TWG was 1.41 g of the 'Bolivia 153' variety, being characterized by slightly larger grains, with TWG of 1.45 g, while the 'Golden Giant' variety formed smaller grains, with a TWG of 1.37 g (Table 6).  Rusu et al. (2009) and Marin et al. (2011), obtained 2,530.36 kg ha -1 of the grains production of Amaranthus sp. on the Somesan Plateau, out of the 12 Amaranthus varieties studied, 7 recorded grains productions over 4,000 kg ha -1 (4 varieties belonging to A. cruentus L. and 3 varieties of A. hypochondriacus L.) (Rusu et al., 2009;Marin et al., 2011).
In our experiments, the grains yields were, in average, 2,002 kg ha -1 in 2017 and 3,023 kg ha -1 in 2018. Regarding grains yields, the 'Golden Giant' variety surpassed the 'Bolivia 153' variety distinctly significant in both 2017 and 2018 years with 91 kg ha -1 , respectively 179 kg ha -1 (Table 7). Also, the same variety has a good production in 2018. Also, in 2018, this variety behaved well, significantly exceeding the average. Chemical composition and quality yields The values for protein content were on average 16.11%. Higher protein content was determined for the 'Golden Giant' variety (17.03%) and lower in the 'Bolivia 153' variety (15.38%) ( Table 8). The starch content was on average 51.7%, with values ranging from 51.0% in the 'Golden Giant' variety to 52.4% in the 'Bolivia 153' variety. Regarding lipids, 'Bolivia 153' is best presented with a content of 6.11%, compared to the 'Golden Giant' variety, at which 5.81% lipids were determined. The cellulose content was on average 13.36%, a higher value, 15.05%, being registered in the 'Golden Giant' variety, and the ash content was on average 3.3%, the highest value, of 3.4%, being analysed in the 'Bolivia 153' variety.
In average, the protein production per ha was 404.9 kg ha -1 . Something more being obtained from the 'Golden Giant' variety, i.e. 530.3 kg ha -1 , and less from the 'Bolivia 153' variety, respectively, 280.0 kg ha -1 (Table  9). The high protein content of the 'Golden Giant' variety is noticeable, of over 16% in 2017 and over 17% in 2018. This proves the superiority of the grains of this variety which exceeded the average very significantly in both years of experimentation compared to the common wheat which has on average around 12-14%.

Conclusions
On average, for two years of experiments, the two varieties of Amaranthus were sowing in the second decade of April (April 17-19), plants emerged after 12-15 days, during the first decade of May and flowering in the last decade of June. From a morphological point of view, amaranth plants were characterized by: 149.8-166.7 cm of height plants; 12-13 steam nodes per plant; 36-38 leaves per plant and 3,301.6-3,357.7 cm-2 plant -1 Leaf Area Index. The harvest maturity was reached in the first decade of September, after 124-127 days of vegetation, in which 839.3-842.4 GDD were accumulated. The productivity elements showed: 92,000-98,000 plants per ha -density of plants; 18.23-31.63 g grains plants -1 ; 1.37-1.59 g TWG. In terms of chemical composition, amaranth grains contain on average: 15.20-17.03% proteins; 51.45-53.2% starch; 6.41-7.11% lipids; 5.05-6.67% cellulose; 3.10-3.41% ash. In both years of research, the most productive variety proved to be the 'Golden Giant' variety, which yield was over 3,000 kg ha -1 and around 400 kg ha -1 proteins. Regarding organic agriculture technology for growing, it is recommended to sow the Amaranthus cruentus varieties in the second half of April, at the distance 50 cm between rows and density of 100,000 grains ha -1 . For weed control, repeated weeding will be applied whenever necessary, manual or mechanical. In conclusion, Amaranthus species reflect a good ability to adapt to the conditions of south part of Romania, and cultivation in organic agriculture conditions, with good yields and high level of quality grains.