INFLUENCE OF SOWING DATES AND SEEDING RATES ON EGYPTIAN CLOVER FORAGE AND SEED YIELDS UNDER EL-SERW ENVIRONMENT

Azza Kh. M. Salem ; Mervat R. I. Sayed ; Sh. A. Aboelgoud

and Fatma S.H. Ismail

Forage Crop Res. Depart. Field Crop Res. Inst. Agri.Res. Center, Giza, Egypt.

Key Words:  Egyptian clover (Trifolium alexandrinum L.), sowing date, seeding rates, forage and seed yields.

ABSTRACT

Field experiments were conducted at the Experimental Farm Station of El-Serw, Domietta Governorate, Agriculture Research Center, Egypt during 2016/2017 and 2017/2018 winter seasons to evaluate the effect of different sowing dates (September 30^th, October 15^th, October 30^th and November 15^th) and seeding rates (20, 25, 30 and 35 kg fed^-1) on forage, quality and seed yields of Egyptian clover cv, Serw -1. The treatments were arranged in a randomized complete block in a split plot arrangement with three replications. The obtained results could be summarized as follows:

-Sowing dates had significantly affected plant height, dry leaves/stem ratio, number of stem m^-2, fresh and dry forage yields (ton fed^-1), crude and digestible protein% in both seasons. The highest value of this traits were obtained with sowing date in October 15^th, however minimum values were recorded with sowing date in November15^th.

-Seeding rates significantly affected plant height, dry leaves/stem ratio, number of stem m^-2, fresh and dry forage yields (ton fed^-1), crude and digestible protein% in both seasons. The results indicated that sowing Egyptian clover at the rate of 30 kg seed fed^-1 produced the highest averages of plant height, fresh and dry forage yields (ton fed^-1), crude protein (CP%) and digestible crude protein (DCP%) at all studied cuts in both seasons. Moreover, seed yield kg fed^-1 were significantly affected by seeding rates where the highest seed yield was recorded with 25kg fed^-1 seed rate compared with other seeding rates in combined analysis.

-The interaction among sowing dates and seeding rates was significantly affected each of fresh and dry and seed yields. The highest yields for fresh and dry, the percentage of crude and digestible protein were of October 15^th with 30 kg fed^-1. Whereas, the highest yield of seed was obtained with sowing date on October 30^th with 25kg seed rate fed^-1.

Egyptian clover (Trifolium alexandrinum L.) is the main and oldest cultivated winter forage leguminous crop in Egypt, which plays an important role in the agricultural system. Annually, less than two million feddans are planting with Egyptian clover. It produces highly palatable and succulent forage from four to six cuttings during the winter season. It is fed as green or dry (hay). 

Egyptian clover is the best crop for sustainable rotation with rice for salt-affected soils. It has a different advantages i.e. high nutritive value and crude protein content, high nutritional quality for animal feed, contributes to soil fertility and improved soil physical and chemical characteristics (El-Nahrawy, 2005).

Many efforts has been done to increase green yield of Egyptian clover and seed production by many prospects i.e. sowing dates, seeding rates, new cultivars, cutting schedules, fertilization, intercropping, seed mixture, salinity tolerance… ects.  The recommended sowing date in Egypt is from mid-September to mid- October. Sowing date and plant density are very important factors in crop production. The optimum sowing date and plant density paves the way for better-use of time, light, temperature, precipitation and other factors (Seyyed et al. (2012).

Under climatic condition change, potential seed yield following forage season is largely affected by the length of vegetation season (Sardana and Norwal, 2000).  Delay in sowing from 1^st October to 15^th November decreased fresh and dry forage yields but increased the seed yield (Virendra et al., 2000). Sowing Egyptian clover on the 15^th of November gives more fresh forage and seed yields than sowing on the 1^st December (Usmani-Khalil et al., 2001). Abdel- Gawad, (2003) found that theplanting date in Oct. 11^th produced higher fresh and dry yield than that of Nov.4^th. Also, he stated that, crude protein percentage for the tested varieties and accessions ranged from 16.72-17.5% and 25.02-26.49% for crude fiber and there was positive correlation between dry matter yield and digestible crude protein. Bakheit et al. (2012) reported that the highest number of heads and seeds head^-1, 1000-seed weight and seed yield were obtained when sowing on the first of October than first of November or December. They added that high temperature during the growing season of Egyptian clover may affect the seasonal distribution of both forage and seed yields. Kandil and Sharief (2016) stated that early planting on Mid-September maximize forage production per unit area and enhancing forage quality. Bakheit et al. (2017) showed that the sowing dates had a significant differences on plant height, leaf/stem ratio, fresh and dry forage yields. Also, the tallest plant was obtained from the plants sown on 15^th of October. The fresh forage yield significant decreased as sowing date were delayed, meanwhile, the dry forage yield increased as planting date was delayed. Mohamed et al. (2017) revealed that the highest number of seeds/ inflorescence, 1000-seed weight and seed yield were obtained from sowing on the 15^th September. This result due to seedproduction istaking place during the period from April to the Mid-June. The results revealed that growth as well as fodder and seed yield traits of Egyptian clover were significantly influenced by sowing dates. (Parvez et al., 2017) and Surinder et al. (2019) showed thatamong different sowing time, maximum plant height, green and dry fodder yield significantly higher on September10^th, whereas number of heads per plant, number of seeds per head and seed yield were significantly higher with sowing date  on  October 20^th. 

Current climatic conditions towards warming especially in Egypt are expected to prolong the changes in the summer season and shortens the winter season and extended in temperature during which Egyptian clover in grown. Thus, it was thought desirable to change the planting date of Egyptian clover to avoid the high temperature effects at the beginning of the full season (Mohamed et al., 2017).

As the recommended sowing date of Egyptian clover is fluctuated between the last week of September to mid October and according to weather changes, sowing dates of Egyptian clover and seeding rates should be investigated to obtain the highest yield of forage, seed and quality taking into consideration planting dates of summer season crops as well as the farmers engagements and field activities. Hence, the objective of this study was to investigate the optimum sowing date and seeding rate to obtain high forage yield, seed and high quality under the environment of El-Serw.     

The present investigation was carried out at the Experimental farm of El-Serw Agricultural Research Station, A.R.C,  Damietta Governorate, Egypt during the two successive winter seasons of 2016/2017 and 2017/2018, respectively. The objectives of the current investigation aimed to study the effect of sowing dates and seeding rates on forage and seed yields of Egyptian clover variety Serw -1. Physical and chemical properties of the experimental site in the two growing seasons are shown in Table (1) which was determined according to Page et al. (1982).

Table (1): Physical and chemical properties of soil in the experimental site  (average of the two seasons).

The experimental design was a randomized complete block in a split plot arrangement with three replications. Four sowing dates (September 30^th, October 15^th, October 30^th andNovember 15^th) located to main plots and seeding rates (20 , 25, 30 and 35 kg fed^-1. of Egyptian clover) were allocated to sub-plots. The sub-plot area was 12 m² (3 X 4m). The preceding summer crop was rice in both seasons. Recommended agricultural practices were done, i.e., recommended fertilizer rates, during seed bed preparation, seeds were inoculated with appropriate Rhizobia (Okadin) before planting, calcium superphosphate (15.5% P₂O₅) was incorporated into soil surface a rate of 150 kg fed^-1. Furthermore, 24 kg K₂O fed^-1 as potassium sulfate 48% K₂O added just before sowing. Nitrogen fertilizer was added as ammonium nitrate (33.5%N) as activation dose of 15 kg N fed^-1 as an encouraging dose after seed germination and before the first irrigation. Irrigation was practiced as traditional furrow irrigation, and the crop was kept weed free by hand and not use pesticides and fungicides. All cultural practices were maintained at optimum level for maximum Egyptian clover productivity. Cutting dates, cutting periods, number of cutting, forage- season length (days), seed harvesting date and period of seed development are shown in Table 2. Temperature data during the study period including maximum and minimum daily temperature measured from sowing date to mean date of physiological maturity in each season and planting data (Table 3).

Table 2: Date of sowing, cutting dates, cutting periods, number of cuttings, forage season length (days), seed harvesting date and period of seed development.

Table (3): Weather data* for El-Serw region during 2017/2018 and 2018/2019 growing seasons.

* Source: Meteorological authority, El-Serw, Egypt.

A-Yields and its attributes:-

1- Plant height (cm).

2- Leaves/ stem %: By dividing the dry weight of leaves over dry weight of stem.

3- Number of stem m^-2

4-Fresh forage yield (ton fed^-1): Plots were hand clipped and weighed in kg plot^-1, then adjusted into ton fed^-1

5- Dry forage yield (ton fed^-1) (fed= feddan = 4200m²): Sub samples of 1 kg plant were dried at 105 ^OC till constant weight and dry matter percentage (DM%) was estimated then dry forage yield (ton fed^-1) was calculated by multiplying fresh forage yield (ton fed^-1) X dry matter percentage, which calculated as:

                   (Weight of dry plants)/ (Weight of fresh plants) X100.

At harvest, a sample of ten heads were obtained from each treatment to calculate the number of heads/m², weight of heads m^-2, number of seeds head^-1, 1000-seed weight as a mean of such treatment and seed yield determine by seed weight kg/ plot and transformed to seed yield kg /fed.

 B-Chemical constituent: Plants samples of each cut in both years were analyzed in the

Forage Crops Research Dep. Lab at Giza to determine:

Fresh samples (250gm) were dried at 70 ^OC until weight constancy.

1-Crude protein percentage (CP %): N content in forage was determined by the Microkelahl method (A.O.A.C., 2005) and then crude protein percentage (CP%). The (CP) content was calculated from the N content (CP = N × 6.25) (Bozkurt and Kaya, 2010).

2-Digestible crude protein (DCP %) was calculated as

DCP= (CP X 0.9115) - 3.62) according to Mcdonald et al. (1994).

3-Crude fiber percentage (CF%): Forage samples were digested in sulpheric acid and sodium hydroxide (1.25N), and crude fiber was determined by the method of A.O.A.C. (2005).

Statistical Analysis:                                                                                                         

Data were statistically analyzed according to Snedecor and Cochran (1990) and treatment means were compared by least significant difference test (LSD) at 0.05 level of significance. Bartlett’s test was done to test the homogeneity of error variance. The test was not significant for all assessed traits, so, the two season’s data were combined.

RESULTS AND DISSCUSION

A- Growth characters   

Data of combined analyses for plant height, dry leaves / stem % and number of stemm-² are presented in Table 4.

Table 4. Plant height (cm), dry leaves/ stem ratio (%) and number of stems/m²of Egyptian clover as affected by sowing dates and seeding rates (combined analyses of 2016/2017 and 2017/2018 seasons).

S₁=September 30^th, S2 = October 15^th, S3= October 30^th, November 15^TH,  R₁=20 kg fad^-1,    R₂= 25kg fad^-1,  R₃=30 kg fad^-1,  R₄=35 kg fad^-1

Results indicated that significant differences were found in the plant height, leaves /stem % and number of stemm^-2 (Table 4).The results over four or three cuts depicted that the Egyptian clover produced much higher plants (70.49cm) when planting was carried out in October 15^th; followed by plants planted in September 30^th and October 30^th as average of 68.09 cm and 66.79 cm, respectively. Delayed planting to November 15^th resulted in a considerable adverse impact on this parameter, where plant height of 64.02 cm was monitored. The Egyptian clover showed maximum growth performance up to October 15^th and plant height decreased gradually with each fortnight delay in sowing. Similar results have been reported by Bakheit et al. (2017).

Significant differences were found among treatments for leave/stem ratio character where, the results exhibited maximum dry leaves/stem % (37.7) when sowing was done in October 30^th; followed by 36.0% in case of planting in October 15^th. Delaying planting to Egyptian clover planted delayed in November 15^th resulted in a considerable negative effect with average of 28.9 %. The results showed that the Egyptian clover plants had maximum leaves bearing when sowing was done in October 30^th, while percent reduced regularly with delay in sowing. Similar results have been reported by Bakheit et al. (2017).

Concerning stems/m² the highest significant number of stems per m² was obtained in October 15^th (225.3). The number of stems m² in the first sowing date in September 30^th (221.0) was significantly lower than that of   October 15^th and higher than that of October 30^th (217.5). It seems the magnitude of weather conditions within the different sowing dates would have significant effect on yield components such as number of stems per m² with regard to Tables (3 and 4). Furthermore, sowing Egyptian clover during the month of October proved to be most efficient for plant growth characters, while delayed planting to November did not prove beneficial for these traits in agree in agreement with the results have been reported by Bakheit et al. (2017).

2. Effect of seeding rates:

The results in Tables (4) revealed that plant height, dry leaves /stem % and number of stem m^-2 were significantly affected by the different seeding rates in all cuts in combined. Plant population is an important growth parameter, where the optimum plant population is necessary to have better stand and yield. Results showed that seeding rate at 30 kg fed^-1 produced the significant highest plants (70.83cm) more than those at 20, 25 and 35 kg fed^-1 with 7.96, 5.84 and 3.24%, respectively. It appears that the increase in plant height following theincrease in plant density was related to the increase in the inter-plant competition over light, water and nutrients. Under these conditions, plant height increases when environmental parameters such as moisture and soil fertility do not limit the growth of plants (Imam and Ranjbar, 2000). Moreover, the decrease in light penetration into middle and lower layers of canopy decreases auxin decomposition and thus, plant height increases as mentioned by Kandil et al. (2005), Bakheit et al. (2012) and Seyyed et al., 2012). With respect to leaves/stem ratio, Seed rate of 20kg fed^-1 produced the maximum ratio 36.2% whereas minimum dry leaves/stem ratio at 32.0% were recorded in seed rate of 35kg fed^-1. All the treatments differed significantly from each another. According to the obtained results, increasing seedingrates from 20 to 30 kg seed fed^-1 caused significant increases in number of stems m^-2 as the highest mean were resulted from using 30 kg seed fed^-1 at all cuts in combined over seasons (Table 4) in agreement with Kandil et al. (2004).  It seems like that the increase of sowing density over 30kg fed^-1 caused significant decrease of number of stems per m². These results are in agreement with what reported by (Kandil, et al., 2004).

The interaction between sowing dates and seeding rates on growth characters exhibited significantly effect on plant height, dry leaves stem % and number stem m^-2 at all studied cuts in combined seasons. The highest plants were recorded when Egyptian clover was sown at October 15^th and seeding rate of 30kg fed^-1, while the lowest values of this character was showed at November 15^th and 20kg fed^-1 seed rate. Similar resultswere obtained by Bakheit et al. (2012).

Data recorded the highest significant value of leaves/stem ratio at sowing data of October 30^th and 20kg fed^-1 seed rate. Similar results were obtained by Bakheit et al. (2012).

 With respect to the number of stems m^-2, data revealed that the highest significant value was recorded when Egyptian clover was sown at October 15^th and applying 30kg fed^-1 seed rate as average of four cuts in combined. Similar results were obtained by Bakheit, et al., (2017).

Fresh and dry forage yields (ton fed^-1):

1. Effect of sowing dates:

Results in Table (5) show that the second sowing date recorded significant higher fresh and dry forage yields than the other sowing dates over seasons and revealed that delay in sowing from October 15^th to October 30^th up to November 15^th decreased total fresh and dry yields by 18.7 and 44.59% for fresh yield and by 5.86 and 8.04% for dry yield, respectively (Table 5). Forage yields decreased with delaying sowing mainly due to the shorter duration of the production season in the later sowing dates, as mentioned by Badawy et al. (2016) and Bakheit et al. (2017). The availability of more cuts could be obtained due to the longer period of growing seasons when cultivation is been carried out between mid September and October where the environment condition at the period of seedling development is mush suitable, as reported by Seyyed et al. (2012).  Moreover, the significant decrease when sowing was at Nov. 15^th was due to the short duration of growth which reflected in less number of cuts comparing to other sowing dates which confirm the results of Sardana and Narwal (2000) and Abdel-Gawad (2003). The results show a change in ecosystem because the general recommendation in relation to sowing date of Egyptian clover October 15^th produced a remarkable high crop yield over the recommended date of sowing; while sowing in November was not beneficial so far the fresh fodder yield per feddan is concerned. The results of the study are in accordance with those of Din et al. (2015) who concluded that Egyptian clover sowing must not be delayed beyond October and also delay of sowing and shortening the growing season decreased the amount of radiation intercepted during the growing season and thus total fresh and dry yield of Egyptian clover. Yield loss due to unfavorable sowing date has been reported in many researchers such as Rastegar (2004).

S₁=September 30^th, S2 = October 15^th, S3= October 30^th, November 15^TH,  R₁=20 kg fad^-1,    R₂= 25 kg fad^-1,  R₃=30 kg fad^-1,  R₄=35 kg fad^-1

Data in Table (5) express that, there was significant effect among seeding rates on both fresh and dry yields fed ^-1 of Egyptian clover at all studied cuts in combined. The increase in seeding rate up to 30 kg fed^-1 had a positive effect on total fresh and dry forage yields in combined, so that total fresh yield at the rate of 30 kg seeds fed^-1 produced the highest values and increases over the other treatments by 18.79, 4.47 and 42.81% for 20, 25 and 35 seeds kg fed^-1, respectively, and for total dry yield were 18.97, 5.56 and 14.34% for 20, 25 and 35, receptively. The increases in forage yield with higher seeding rates up to 30kg attributed to high values of plant height and number of stem m^-2 as indicated in Table (4). Fresh and dry yields were significantly lower than other rates when seed rate was increased to 35kg. These findings are in accordance with those stated by Sardana and Narwal (2000) and Kandil et al. (2004).

3. Effect of the interaction:

The interaction between sowing dates and seeding rates (Table 5) exhibited significantly effect on fresh and dry forage yields (ton fed^-1) at all studied cuts in combined seasons. The highest fresh and dry yields (ton fed^-1) were obtained when Egyptian clover was sown in October 15^th with seeding rate of 30 kg fed^-1 (45.26 ton fed^-1) significantly higher than what obtained from other dates of cultivation combined with different rates of seeds under El-Serw environment. The lowest yields were achieved (20.7 t.fed^-1) when sowing date was (Nov. 15^th) combined with 20kg fed ^-1 seeding rate. The obtained results is almost true, as it is agree with what revealed by Abdel-Gawad (2003) and Kandil et al. (2004) stated that the maximum forage yield of Egyptian clover was achieved when it was cultivated at seeding rate of 30 kg fed^-1 in the mid of October under the environment of Dakahlia Gov. which located near by Domieta Gov. which almost have the same environment.

C-Chemical constituents:-

Results in Table (6) showed the effect of sowing dates and seeding rates on crude protein, digestible crude protein and crude fiber %.

1. Effect of sowing dates:

The results showed that crude protein, digestible crude protein and crude fiber percentages of Egyptian clover were significantly affected by sowing dates (Table 6). Over both seasons the highest value of crude protein and digestible crude protein was recorded up to October 15^th, While, decreased gradually with each fortnight delay in the sowing. Means comparison indicated that with the delay in sowing date, crude protein was decreased by 12.45 and 16.86% at the sowing dates of September 30^th and October 15^th compared with the sowing date of November 15^th, respectively (Table 6). The significant decrease in crude protein caused by the delay in sowing can be associated with lower temperatures at the third and fourth sowing dates which limited their growing period and assimilate-building. DCP% behaved the same trend of CP % in combined. Similar finding was reported byPea and Bin (2001) and Abdel-Gawad (2003).

Table 6. Crude protein (CP%), digestible crude protein (DCP %)) and crude fiber (CF%) of Egyptian clover as affected by sowing dates and seeding rates (combined of 2016 / 2017 and 2017/2018 seasons)

S₁=September 30^th, S2 = October 15^th, S3= October 30^th, November 15^TH,  R₁=20 kg fad^-1,    R₂=  25kg fad^-1,  R₃=30 kg fad^-1,  R₄=35 kg fad^-1