The Effect of Planting Date on Thermal Indices and Dry matter Yield of Different Clover Species
الموضوعات :
Mohammad Zamanian
1
(Seed and Plant Improvement Institute, Agricultural Research, Education and Extension Organization (AREEO), Karaj, Iran)
Mona Poureisa
2
(Department of Agriculture, Payame Noor University Tehran-Iran)
Farid Golzardi
3
(Seed and Plant Improvement Institute, Agricultural Research, Education, Extension Organization, Karaj, Iran)
الکلمات المفتاحية: Trifolium, Growing degree-day (GDD), Growth rate, Heat use efficiency (HUE), Photothermal index (PTI),
ملخص المقالة :
This study aimed to investigate the changes in thermal indices of various clover genotypes under cold stress. A field experiment was conducted to evaluate the effect of different planting dates (14 Sep., 28 Sep., and 8 Oct.) and clover genotypes (late-maturity Persian clover, mid-maturity Persian clover, early-maturity Persian clover, berseem clover, red clover, and crimson clover). The results showed that delaying the planting date from September 14 to October 8 caused a significant decrease in growing degree-day (GDD), photothermal index (PTI), and heat use efficiency (HUE) in all studied genotypes. Early-maturity Persian clover and crimson clover had the lowest thermal requirements, while red clover had the highest GDD in all the investigated planting dates. During the first cut, the early-maturity Persian clover demonstrated the highest HUE (4.09 kg ha-1 °C days), followed by crimson clover. In contrast, red clover recorded the lowest HUE (1.43 kg ha-1°C days) on the last planting date. Early-maturity Persian clover and crimson clover may be preferred for forage production under cold stress due to their higher HUE values. The highest dry matter yield of the first cut (6300 kg ha-1) was obtained on the first planting date and by mid-maturity Persian clover, while the lowest yield (2429 kg ha-1) was obtained on the last planting date and by red clover. Overall, delayed planting dates resulted in accelerated development and decreased thermal requirements in clover species. The early-maturity genotypes were found to be more suitable for forage production under environmental stresses such as water shortages.
Aktar-Uz-Zaman, M., M. A. Haque, A. Sarker, M. A. Alam, M. M. Rohman, M. O. Ali, M. A. Alkhateeb, A. Gaber and A. Hossain. 2022. Selection of lentil (Lens culinaris (Medik.)) genotypes suitable for high-temperature conditions based on stress tolerance indices and principal component analysis. Life, 12 (11): 1719.
Alizadeh, M.A. and A.A. Jafari. 2011. Effect of cold temperature and growth degree-days on morphological and phonological development and quality characteristics of some ecotypes of Cocksfoot (Dactylis glomerata). Middle-East Journal of Scientific Research, 7 (4): 561-566.
Anil, K., V. Pandey, A.M. Shekh and M. Kumar. 2008. Growth and yield response of soybean in relation to temperature, photoperiod and sunshine duration at Anand, Gujarat, India. American-Eurasian Journal of Agronomy, 1 (2): 45-50.
Ashoori, N., M. Abdi, F. Golzardi, J. Ajalli and M.N. Ilkaee. 2021. Forage potential of sorghum-clover intercropping systems in semi-arid conditions. Bragantia, 80: e1421.
Bakhtiyari, F., M. Zamanian and F. Golzardi. 2020. Effect of mixed intercropping of clover on forage yield and quality. South Western Journal of Horticulture, Biology and Environment, 11 (1): 49-66.
Balazadeh, M., M. Zamanian, F. Golzardi and A. Mohammadi Torkashvand. 2021. Effects of limited irrigation on forage yield, nutritive value and water use efficiency of Persian clover (Trifolium resupinatum) compared to Berseem clover (Trifolium alexandrinum). Communications in Soil Science and Plant Analysis, 52 (16): 1927-1942.
Butler, T. J., G. W. Evers, M. A. Hussey and L. J. Ringer. 2002. Flowering in crimson clover as affected by planting date. Crop Science, 42 (1): 242-247.
Clapham, W. M. and J. M. Fedders. 2004. Modeling vegetative development of berseem clover (Trifolium alexandrinum L.) as a function of growing degree days using linear regression and neural networks. Canadian Journal of Plant Science, 84(2): 511-517.
Dinari, A., F. Meighani and M. Farzami Sepehr. 2013. Effects of salt and drought stress on germination and seedling growth of Avena fatua and Phalaris minor. Iranian Journal of Plant Physiology, 3 (2): 665-671.
Iannucci, A., M. R. Terribile and P. Martiniello. 2008. Effects of temperature and photoperiod on flowering time of forage legumes in a Mediterranean environment. Field Crops Research, 106 (2): 156-162.
Jan, B., M. A. Bhat, T. A. Bhat, M. Yaqoob, A. Nazir, M. A. Bhat and A. T. K. Zuan. 2022. Evaluation of seedling age and nutrient sources on phenology, yield and agrometeorological indices for sweet corn (Zea mays saccharata L.). Saudi Journal of Biological Sciences, 29(2): 735-742.
Kingra, P.K. and P. Kaur. 2012. Effect of dates of sowing on thermal utilization and heat use efficiency of groundnut cultivars in central Punjab. Journal of Agricultural Physics, 12 (1): 54- 62.
Kumar, R., M. Kaundal, S. K. Vats and S. Kumar. 2012. Agrometeorological indices of white clover (Trifolium repens) in western Himalayas. Journal of Agrometeorology, 14 (2): 138-142.
Mirahki, I., M.R. Ardakani, F. Golzardi, F. Paknejad and A. Mahrokh. 2023. Yield, water use efficiency and silage feeding value of sorghum cultivars as affected by planting date and planting method. Gesunde Pflanzen, 75: 1-11. https://doi.org/10.1007/s10343-022-00822-z.
Nematollahi, D., H. R. Eisvand, A.M. Modares Sanavi, N.Akbari and A. Ismaili. 2017. The effects of various levels of water deficit stress on forage yield and physiological characteristics of four cultivars of clover (Trifolium spp) under low input condition. Iranian Journal of Plant Physiology, 7 (3): 2125-2134.
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Papastylianou, P.T. and D. Bilalis. 2011. Flowering in Sulla and Persian clover as effected by sowing date in a Mediterranean environment. Australian Journal of Crop Science, 5 (10): 1298-1304.
Shahrusvand, S., H. Eisvand, F. Nazarian and M. Feizian. 2020. The Soybean photosynthesis response, yield, and grain quality affected by vermicompost and sulfur. Iranian Journal of Plant Physiology, 10 (3): 3233-3241.
Shamsi, K., S. Kobraee and B. Raseki. 2011. The effect of different planting densities on seed yield and quantitative traits of rainfed chickpea varieties. African Journal of Agricultural Research, 6 (3): 655-659.
Singh, M.P., L. Lallu and N.B. Singh. 2014. Thermal requirement of Indian mustard (Brassica juncea) at different phonological stages under late sown condition. Indian Journal of Plant Physiology, 19 (3): 238-243.
Zamanian, M. 2018. Effect of low temperature stress on physiological characters of Persian clover species. Journal of Plant Process and Function, 6 (19): 181-192
Zamanian, M., M. Poureisa and A. Baghbani-Arani. 2021a. Changes in soluble carbohydrate and starch concentration and root morphological characteristics in clover Trifolium spp. genotypes under cold stress. Iranian Journal of Plant Biology, 13 (1): 83-106.
Zamanian, M., M. Poureisa and A. Baghbani-Arani. 2021b. Change of fatty acid profiles in clover genotypes induced by cold stress. Journal of Plant Process and Function, 10 (43): 65-74.
1405
The effect of planting date on thermal indices and dry matter yield of different clover genotypes
Mohammad Zamanian*, Mona Poureisa, and Farid Golzardi
Seed and Plant Improvement Institute, Agricultural Research, Education, and Extension Organization (AREEO), Karaj, Iran
________________________________________________________________________________
Abstract
This study aimed to investigate the changes in thermal indices of various clover genotypes under cold stress. A field experiment was conducted to evaluate the effect of different planting dates (14 Sep., 28 Sep., and 8 Oct.) and clover genotypes (late-maturity Persian clover, mid-maturity Persian clover, early-maturity Persian clover, berseem clover, red clover, and crimson clover). The results showed that delaying the planting date from September 14 to October 8 caused a significant decrease in growing degree-day (GDD), photothermal index (PTI), and heat use efficiency (HUE) in all studied genotypes. Early-maturity Persian clover and crimson clover had the lowest thermal requirements while red clover had the highest GDD in all the investigated planting dates. During the first cut, the early-maturity Persian clover demonstrated the highest HUE (4.09 kg ha-1 ℃ days), followed by crimson clover. In contrast, red clover recorded the lowest HUE (1.43 kg ha-1 ℃ days) on the last planting date. Early-maturity Persian clover and crimson clover may be preferred for forage production under cold stress because of their higher HUE values. The highest dry matter yield of the first cut (6300 kg ha-1) was obtained on the first planting date and by mid-maturity Persian clover while the lowest yield (2429 kg ha-1) was obtained on the last planting date and by red clover. Overall, delayed planting dates resulted in accelerated development and decreased thermal requirements in clover species. The early-maturity genotypes were found to be more suitable for forage production under environmental stresses such as water shortages.
Keywords: trifolium, growing degree-day (GDD), growth rate, heat use efficiency (HUE), photothermal index (PTI)
Zamanian, M., M. Poureisa, and F. Golzardi. 2024. 'The effect of planting date on thermal indices and dry matter yield of different clover genotypes'. Iranian Journal of Plant Physiology 14(1), 4787- 4798.
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____________________________________ * Corresponding Author E-mail Address: m.zamanian@areeo.ac.ir Received: January, 2021 Accepted: June, 2023
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Climate is one of the uncontrollable factors that significantly influence the growth and development of crops (Dinari et al., 2013; Shahrusvand et al., 2020; Pakbaz et al., 2022). Temperature, among other climatic factors, has the most substantial impact on crop development, phenological stages such as flowering, and crop yield (Iannucci et al., 2008). Crops require a certain amount of heat to reach each developmental stage, as per the principle of thermal stability (Nleya et al., 2020; Mirahki et al., 2023). Given the variability of day length and daily temperature, the use of thermal indices, particularly GDD are necessary to estimate crop phenological stages (Butler et al., 2002). Therefore, it is crucial to determine the thermal indices of different phenological stages to exploit the maximum potential of crop production (Mirahki et al., 2023). Growing degree-day (GDD), photothermal index (PTI), and heat use efficiency (HUE) are the most important thermal indices, calculated based on temperature and day length, and are used to predict the phenological stages and yield of crops (Butler et al., 2002; Iannucci et al., 2008; Kumar et al., 2012; Aktar-Uz-Zaman et al., 2022).
Papastylianou and Bilalis (2011) reported that Persian clover requires 322 to 379 ℃ days fewer GDD and 144 to 173 ℃ days day-1 fewer PTI to reach the early and full flowering stages than Sulla. Shamsi et al. (2011) reported that different phenological stages of chickpea varieties require specific amounts of GDD and HUE. Alizadeh and Jafari (2011) found that Dactylis glomerata ecotypes had a higher heat requirement at the vegetative growth stage than at the flowering stage under cold stress, indicating no effect of cold on the amount of GDD required at the seedling and vegetative growth stages. Kingra and Kaur (2012) reported that HUE increased from vegetative growth to grain filling and physiological maturity in peanuts. They also found that delayed planting reduced HUE, with the highest and lowest values of HUE related to the first and last planting dates, respectively. The PTI decreased gradually from emergence to maturity, with the highest amount occurring at the emergence stage and the lowest at the maturity stage. Also, among the three planting dates, the highest and lowest PTI were recorded for January 1 and July 10, respectively (Kingra and Kaur, 2012). Anil et al. (2008) investigated the growth and yield responses of soybean to temperature and photoperiod and found that HUE increased with increasing crop age and delayed planting. Butler et al. (2002) conducted a study on the effect of planting date on the thermal indices of various cultivars of crimson clover and found that Tibbee required fewer GDD and PTI units than Columbus. The study also revealed that delayed planting date resulted in decreased GDD and PTI values (Butler et al., 2002). In a more recent study, Jan et al. (2022) found that transplanting 22-day-old seedlings and applying poultry manure resulted in higher HUE, indicating a more efficient use of thermal energy for biomass production. Sarparast and Alipour Nakhi (2021) investigated the impact of different planting dates ranging from July 23 to September 6 on the thermal indices of fava bean and found that the highest HUE was observed in crops planted on August 6, indicating that this may be the optimal planting date to maximize the thermal efficiency of fava bean production.
Clover holds a crucial position in forage production in Iran (Bakhtiyari et al., 2020; Ashoori et al., 2021), and therefore, determining its accurate ecological requirements is essential for successful crops and maximum forage production (Balazadeh et al., 2021). Estimating the growth period of different clover species based on thermal indices is crucial in identifying suitable areas for cultivation and developing effective crop management strategies. The objective of the present study was to estimate the thermal indices that affect the phenological stages and yield of clover genotypes at different planting dates in a semi-arid region of Iran, with the aim of optimizing climatic factors for higher forage production.
Materials and Methods
Fig. I. Daily maximum and minimum air temperatures (°C) and precipitation (mm) during the growing seasons Table 1 Number of frost days and number of sunny days during the growing seasons
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Table 2 Physico-chemical properties of soil at the experimental site during two growing seasons
EC: electrical conductivity, O.M.: organic matter, N: total nitrogen, P: available phosphorus, K: available potassium
Table 3 Name and origin of clover genotypes
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A field experiment was conducted as split plots based on a randomized complete block design with four replications. Planting date was considered the main factor, with three levels (14 September, 28 September, and 8 October), and clover genotypes were considered as the sub-factor, with six levels (late-maturity Persian clover, mid-maturity Persian clover, early-maturity Persian clover, berseem clover, red clover, and crimson clover). Table 3 presents the characteristics of the clover genotypes. Each plot consisted of four rows measuring 0.5 m wide and 10 m long. Persian and red clover were sown at a rate of 20 kg ha-1 while berseem and crimson clover were sown at a rate of 25 kg ha-1. According to the soil analysis result, 90 kg P2O5 ha-1 and 40 kg N ha-1 were supplied before planting. The criteria for the occurrence and recording of each stage of growth and forage yield harvest at each planting date were the mean of those stages in each plot. The GDD was calculated by recording the growth stages and having day-night time temperatures. The two-year average of the number of days and temperatures required for each growth stage was the criterion for GDD. The GDD was calculated using the following formula (Singh et al., 2014):
GDD = Σ {[(Tmax + Tmin) / 2] –Tbase}
where Tmax, Tmin, and Tbase are the daily maximum and minimum temperatures and also the base temperature (5 ℃), respectively. The following formulas were used to measure PTI (℃ days day-1) and HUE (kg ha-1/℃ days) indices (Singh et al., 2014):
HUE = Dry matter yield / GDD
PTI = GDD / Growth days
The effective temperature summation method was employed in this study, where temperatures below 5 and above 30 ℃ were considered ineffective and assigned values of 5 and 30 ℃, respectively (Nleya et al., 2020). Bartlett's test results indicated homogeneity of experimental error variances over two years, and therefore, combined analysis of variance was performed. Since the interaction between year and treatment on traits was not significant, an average of the two seasons was reported, with the year treated as a random effect. Statistical analysis was carried out using SAS 9.1 statistical software, and mean values were compared using the LSD method at the 5% probability level.
Results
Growing degree days (GDD)
Fig. II. Growing degree-day (GDD) in clover genotypes
Fig. III. Growing degree-day (GDD) in different planting dates |
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Analysis of variance of thermal indices as affected by experimental treatments
* and **: significant at the 5% and 1% probability levels, respectively.
Table 5 Mean comparison of growing degree-days (GDD, ℃ days) required for forage production of clover genotypes in different cuts
In each column and for each factor, means followed by the same letters are not significantly different at the 5% probability level.
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Fig. IV. Interaction effect of planting date and genotype on the growing degree-days of clover Table 6 Mean comparison of photo thermal index (PTI, ℃ days day-1) for forage production of clover genotypes in different cuts
In each column and for each factor, Means followed by same letters are not significantly different at the 5% probability level.
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Fig. V. Photo thermal index (PTI) in clover genotypes
Fig. VI. Photo thermal index (PTI) in different planting dates |
Photo thermal index (PTI)
Fig. VIII. Heat use efficiency (HUE) in clover genotypes
Fig. IX. Heat use efficiency (HUE) in different planting dates
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Fig. VII. Interaction effect of planting date and genotype on the photo thermal index of clover Table 7 Mean comparison of heat unit efficiency (HUE, kg ha-1 / ℃ days) in forage production of clover genotypes in different cuts
In each column and for each factor, means followed by same letters are not significantly different at the 5% probability level.
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Heat use efficiency (HUE)
Fig. X. Interaction effect of planting date and genotype on the heat use efficiency of clover Table 8 Mean comparison of dry matter yield (kg ha-1) of clover genotypes in different cuts
In each column and for each factor, means followed by same letters are not significantly different at the 5% probability level.
Fig. XI. Interaction effect of planting date and genotype on the dry matter yield of clover
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Dry matter yield
The dry matter yield was significantly influenced by planting date, genotype, and planting date × genotype interaction, as shown in Table 4. The mid-maturity Persian clover, berseem clover, and red clover cultivars exhibited the highest dry matter yields in the first, second, and third cut, respectively, with yields of 5265, 7038, and 3346 kg ha-1, respectively (Table 8). Berseem clover had the highest total yield (13429 kg ha-1) while the mono-cut species had the lowest yield, as shown in Table 8. The results also revealed that delaying the planting date had a negative impact on the dry matter yield, with yield decreasing and reaching a minimum on the last planting date (Fig. XI). The highest forage yield in the first cut was obtained by planting the mid-maturity Persian clover on the first planting date while the lowest yield was recorded in red clover and the last planting date. Notably, the delay in planting had the most significant negative effect on the yield of red clover, with each day of delay resulting in a decrease by approximately 120 kg ha-1 in dry matter yield (Fig. XI).
Discussion
The obtained results revealed a strong impact of planting date, genotype, and their interaction on the GDD, PTI, HUE and dry matter yield in clover genotypes. Findings clearly highlight the importance of these factors in optimizing forage production, with clear implications for crop management practices (Butler et al., 2002; Kumar et al., 2012). According to our results, there is a distinctive differentiation among clover genotypes based on their GDD requirements, where the genotypes can be grouped into late-, mid-, and early-maturity groups (Aktar-Uz-Zaman et al., 2022). Red clover, with the highest GDD requirement across all cuts, and Persian clover cv. KPC-PL require the maximum heat for forage production, placing them in the late-maturity group. This indicates that these genotypes might be more suitable for regions with longer growing periods and higher temperatures (Clapham and Fedders, 2004). Conversely, early-maturity Persian clover cv. KPC-PE and crimson clover cv. Alborz1, with the least heat requirements, fall into the early-maturity group, implying a potential advantage in cooler climates or shorter growing seasons (Zamanian et al., 2021b). The data also illustrates an inverse relationship between planting date and GDD, with later planting dates causing reduced thermal requirements in all studied genotypes. This was most prominent in crimson clover and Persian clover cv. KPC-PE, highlighting the adaptability of these genotypes to colder conditions or late planting scenarios (Butler et al., 2002). Early-maturity cultivars generally need lower temperatures for flowering compared to late-maturity genotypes. For this reason, early genotypes can also be used for fodder production in cold and semi-cold regions (Papastylianou and Bilalis, 2011). Similar to the present study, Butler et al. (2002) reported that Tibbee cultivar of crimson clover required fewer GDD than other genotypes, and delaying the planting date resulted in reduced GDD values across all cultivars.
The PTI results further expand our understanding of the genotype and maturity differences. Red clover and late-maturity Persian clover consistently showed the highest PTI, suggesting a greater ability to utilize longer periods of light and heat for growth (Iannucci et al., 2008). Conversely, early-maturity Persian clover and crimson clover had the lowest PTI, aligning with their lower GDD requirements. Delayed planting was found to reduce PTI in all genotypes, and this reduction was more pronounced in early-maturity cultivars. The decrease in PTI resulting from delayed planting has been reported by both Butler et al. (2002) and Kumar et al. (2012). In terms of HUE, early-maturity Persian clover and crimson clover demonstrated superior heat use efficiency in the first cut, potentially enabling them to optimize growth under lower temperatures (Kumar et al., 2012; Zamanian et al., 2021b). However, this advantage was not consistent across all cuts, indicating the dynamic nature of HUE across the growing season. Delayed planting was found to reduce HUE, with the third planting date being most affected, reinforcing the importance of careful timing in planting decisions (Kumar et al., 2012). One of the reasons for the low thermal requirements of crimson clover and early-maturity Persian clover is the short duration of their growth period, earliness, and producing only one cut forage per season (Bakhtiyari et al., 2020; Zamanian et al., 2021a). Accordingly, crimson clover and early-maturity Persian clover could be cultivated in areas with water deficit for fresh forage production during spring (Zamanian et al., 2021b). In the first cut, red clover had the highest GDD and the lowest dry matter yield due to their long vegetative growth and lack of stem production (Balazadeh et al., 2021), which resulted in lowest HUE. However, , this trend reversed in the second cut and berseem clover reached a higher rate due to faster growth than other genotypes (Nematollahi et al., 2017). Also, in red clover, due to a more balanced growth rate and forage production in spring and summer (more cuts), HUE showed a more balanced trend than all other genotypes in all cuts (Zamanian, 2018). Similar to the results of the present study, Kingra and Kaur (2012) reported that the HUE decreased in delayed planting, so that the highest and lowest HUEs were recorded at the first and last planting dates, respectively (Kingra and Kaur, 2012). Meanwhile, Anil et al. (2008) reported that HUE and PTI increase with the aging of the plant and the delay in the planting of soybean in warm regions. Therefore, thermal indices may be different based on the species and climatic conditions.
The analysis of dry matter yield further emphasized the impact of genotype and planting date. Mid-maturity Persian clover, berseem clover, and red clover cultivars exhibited the highest yields in the first, second, and third cut, respectively. The variation in yield among different clover cultivars in different cuts can be attributed to several factors, including their growth habits, nutrient requirements, and environmental adaptability (Zamanian, 2018; Balazadeh et al., 2021). The highest total yield was achieved by berseem clover, whereas mono-cut species yielded the least. Berseem clover tends to have a more prostrate growth habit and is better adapted to mid-season production (Clapham and Fedders, 2004). This means that it may not produce as much in the first cut, but can excel in the second cut when conditions are more suitable for its growth (Ashoori et al., 2021; Balazadeh et al., 2021).
Delaying the planting date negatively impacted the dry matter yield of all genotypes, emphasizing the importance of optimal planting timing for maximizing yield. Delayed planting can result in a shorter growing season for the plants, which means they have less time to grow and produce biomass (Nleya et al., 2020; Mirahki et al., 2023). If the plants are also exposed to the first cold of the season during this shortened growing period, it can further reduce their ability to produce dry matter (Alizadeh and Jafari, 2011; Zamanian et al., 2021a). Notably, red clover was the most affected by delayed planting, experiencing a substantial decrease in dry matter yield with each day of delay. These results collectively underscore the significance of genotype and planting date choice in optimizing forage production (Mirahki et al., 2023). They highlight the adaptability of different clover genotypes to various temperature conditions and planting scenarios, providing valuable guidance for farmers and crop managers in their decision-making processes (Balazadeh et al., 2021). Future research should delve deeper into understanding the underlying mechanisms responsible for these observed differences, which would facilitate the development of optimized cropping systems.
Conclusion
The present study highlights the significant influence of the interaction between planting date and genotype on the thermal requirements and dry matter yield of clover. Specifically, the early-maturity Persian clover cv. KPC-PE and crimson clover cv. Alborz1 had lower GDD and PTI across all the planting dates investigated. These results indicate that cultivating early-maturity cultivars could be advantageous for fodder production in areas with a short growing season or under conditions of delayed planting. Furthermore, timely planting is crucial for late cultivars such as red clover, which require more time to establish properly. Delayed planting of late-maturity genotypes, particularly red clover, in autumn cultivation is risky in cold regions due to their high thermal requirement. Therefore, the heat requirement of the studied cultivars should be considered when selecting appropriate species for cultivation, and delayed planting of late-maturity genotypes should be avoided in cold regions. Crimson clover and early-maturity Persian clover genotypes had a minor thermal requirement, and thus, these species can be used in crop rotation systems to produce fodder in short intervals between the cultivation of two main crops. Furthermore, these species are suitable for fodder production in areas facing water shortage crisis, as autumn cultivation provides the possibility of using rain and green water while minimizing pressure on underground water resources.
This study proposes that autumn cultivation of early-maturity clover cultivars can be a practical solution to meet the country's need for fresh fodder in the early growing season. This strategy optimally utilizes available water for spring cultivation while providing fresh fodder and minimizing the pressure on underground water resources. Thus, the findings of this study have important implications for the development of sustainable and efficient forage production systems. Overall, the study suggests that if there is a sufficient growing season, berseem clover and late-maturity Persian clover, with the production of three cuts of forage, are optimal choices, and should be planted without delay, ideally in mid-September. However, in situations where the growing season is limited, or there is an urgent need for fodder, or a forced delay in planting, it is better to choose crimson clover and early-maturity Persian clover. Nonetheless, similar to late-maturity cultivars, it is still advisable to plant early-maturity cultivars as soon as possible.
References
Aktar-Uz-Zaman, M., M. A. Haque, A. Sarker, M. A. Alam, M. M. Rohman, M. O. Ali, M. A. Alkhateeb, A. Gaber and A. Hossain. 2022. Selection of lentil (Lens culinaris (Medik.)) genotypes suitable for high-temperature conditions based on stress tolerance indices and principal component analysis. Life, 12 (11): 1719.
Alizadeh, M.A. and A.A. Jafari. 2011. Effect of cold temperature and growth degree-days on morphological and phonological development and quality characteristics of some ecotypes of Cocksfoot (Dactylis glomerata). Middle-East Journal of Scientific Research, 7 (4): 561-566.
Anil, K., V. Pandey, A.M. Shekh and M. Kumar. 2008. Growth and yield response of soybean in relation to temperature, photoperiod and sunshine duration at Anand, Gujarat, India. American-Eurasian Journal of Agronomy, 1 (2): 45-50.
Ashoori, N., M. Abdi, F. Golzardi, J. Ajalli and M.N. Ilkaee. 2021. Forage potential of sorghum-clover intercropping systems in semi-arid conditions. Bragantia, 80: e1421.
Bakhtiyari, F., M. Zamanian and F. Golzardi. 2020. Effect of mixed intercropping of clover on forage yield and quality. South Western Journal of Horticulture, Biology and Environment, 11 (1): 49-66.
Balazadeh, M., M. Zamanian, F. Golzardi and A. Mohammadi Torkashvand. 2021. Effects of limited irrigation on forage yield, nutritive value and water use efficiency of Persian clover (Trifolium resupinatum) compared to Berseem clover (Trifolium alexandrinum). Communications in Soil Science and Plant Analysis, 52 (16): 1927-1942.
Butler, T. J., G. W. Evers, M. A. Hussey and L. J. Ringer. 2002. Flowering in crimson clover as affected by planting date. Crop Science, 42 (1): 242-247.
Clapham, W. M. and J. M. Fedders. 2004. Modeling vegetative development of berseem clover (Trifolium alexandrinum L.) as a function of growing degree days using linear regression and neural networks. Canadian Journal of Plant Science, 84(2): 511-517.
Dinari, A., F. Meighani and M. Farzami Sepehr. 2013. Effects of salt and drought stress on germination and seedling growth of Avena fatua and Phalaris minor. Iranian Journal of Plant Physiology, 3 (2): 665-671.
Iannucci, A., M. R. Terribile and P. Martiniello. 2008. Effects of temperature and photoperiod on flowering time of forage legumes in a Mediterranean environment. Field Crops Research, 106 (2): 156-162.
Jan, B., M. A. Bhat, T. A. Bhat, M. Yaqoob, A. Nazir, M. A. Bhat and A. T. K. Zuan. 2022. Evaluation of seedling age and nutrient sources on phenology, yield and agrometeorological indices for sweet corn (Zea mays saccharata L.). Saudi Journal of Biological Sciences, 29(2): 735-742.
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