Effect of Defoliation Time on Rye Yield and Its Quality under Dual-Purpose Cultivation for Roughage and Concentrate Production

Abstract

A dual-purpose cultivation system allows cereals to produce both roughage and concentrate during one growing season. To establish a cultivation system for rye, the appropriate time for foliage mowing was determined to ensure a yield of nutrient-rich roughage from the first crop and abundant grain from the second crop. This is because the stage of growth at defoliation affects the yield and quality of both crops. The experimental rye line ‘4R-504’ was grown in two successive cropping seasons; 2019/2020 and 2020/2021. Foliage was mowed at three different growth stages: the booting stage (BT), the early-heading stage (EH), and the fully heading stage (FH). Along with the growth stage, the plants grew taller, and the highest dry matter yield in the first crop was observed in FH (757 g m⁻²), which was 1.5 times higher than that in BT (480 g m⁻²). Although the nutritional value was higher in plants harvested at an earlier growth stage, the EH and FH plants showed a higher dry matter yield, resulting in a higher production of metabolizable energy per area. Plants that had been mowed earlier regrew vigorously and produced an abundant amount of grains in the second crop. BT showed the highest grain yield of 239 g m⁻², which corresponds to 60% of the yield from the unmowed control. FH produced grains of only 76 g m⁻², which barely met the requirement of the dual-purpose cropping system. To enhance the nutritional yield of roughage, it is recommended to harvest the first crop at the early heading stage. Conversely, to achieve a higher grain yield, defoliation should be carried out during the booting stage.

1. Introduction

The self-sufficiency rate for livestock feed in Japan, which includes both roughage and concentrate, is relatively low, at only 25% [1]. To reduce import dependence in livestock farming, the Ministry of Agriculture, Forestry and Fisheries of Japan has prioritized increasing fodder production [2,3]. In particular, there has been a growing need for intensive fodder production from paddies and common fields because the total area of artificial meadowland in the country has gradually decreased due to farmers retiring and abandoning cultivation [4].

In the northern region of Japan, farmers often cultivate fodder corn and cereals such as oat and barley for animal feed [5,6]. The foliage of these crops can be used as nutritious roughage, while their matured grains can provide valuable concentrate as a source of starch. In these crops, the translocation of nutrients stored in the vegetative parts to the grains occurs after the flowers have developed. Therefore, if the plants are harvested when they are fully mature, their nutritional value will deteriorate, rendering them useless as roughage [7,8]. Harvesting at an earlier stage can produce nutritious roughage; however, it will not result in any grain production, of course. This indicates that fodder corn and common cereals can only produce either roughage or concentrate during a single cropping, demonstrating a limited flexibility in production.

Rye (Secale cereale L.) is a tall-statured cereal primarily grown as a food crop in cool temperate regions. With its abundant biomass, the green foliage of rye is occasionally utilized as roughage, particularly in the production of silage [9]. Mature grains are also available as a concentrate that is rich in starch and minerals [10,11]. In addition, rye is also unique in its growth. If the foliage is mowed before the flowering stage, the stubble will regenerate and produce a second crop, which will eventually yield grain [12,13,14]. This practice can be utilized in implementing a dual-purpose cropping system, where the first crop is used for roughage and the subsequent second crop is used for concentrate (grains) [15].

Regarding the dual-purpose cropping system of cereals that has been practiced thus far, the main challenge has been determining when to defoliate the first crop [16,17,18]. Foliage removal at an earlier growth stage encourages rapid regrowth, resulting in a good grain yield in the second crop, while producing a small amount of roughage. Delaying the removal of forage achieves a high yield of roughage, but negatively affects the regrowth ability. In the case of rye, in order to obtain both high-nutrient foliage and a productive second crop, the tillering stage is considered to be the optimal time for defoliation [13,14,15]. Meanwhile previous attempts at the dual-purpose cropping system of rye were exclusively based on the assumption that the first crop would be utilized for grazing [14,19]. This implies that defoliation would be carried out during the vegetative growth stage when the plants are still small in size. In northern Japan, however, it is difficult to graze livestock on paddies or common crop fields due to the geographical distance between livestock farming areas and field cropping. As a result, the primary use of fodder cereals, such as rye, is for mowing. Therefore, the first crop harvest will inevitably take place after the initiation of the reproductive growth stage, when the plants have grown significantly large. It is considered that defoliation during the vegetative growth stage and reproductive growth stage exerts a different impact on subsequent growth and grain production of the aftermath. This study aimed to investigate the optimal timing for foliage mowing to maximize the yield of high-nutrient roughage from the first crop and abundant grain from the second crop. The goal is to establish a dual-purpose cropping system for rye.

2. Materials and Methods

2.1. Cultivation of Rye

The field experiments were conducted at the experimental field of Obihiro University of Agriculture and Veterinary Medicine, Obihiro, Hokkaido prefecture, Japan (42.9° N, 143.2° E, and 77.8 m above sea level), for two consecutive cropping seasons: 2019/2020 and 2020/2021. The soil type of the field was andosol with a pH range of 6.2–6.4, containing approximately 4 mg of available nitrogen, 40mg of available phosphate and 60 mg of exchangeable potassium per 100 g of soil. The climate at the field is characterized by an average annual temperature of 7.2 °C and an annual precipitation of 920 mm [20]. From late December to late March, the field was covered with approximately 50 cm of snow.

The unregistered experimental winter rye line ‘4R-504’ was used for the experiments. This line is suitable for fodder use due to its superior biomass productivity and abundance of tall tillers. Seed sowing took place on 28 September 2019 and 30 September 2020, respectively. The seeds were sown at a density of 100 seeds per square meter, with a planting interval of 4 cm and a row spacing of 25 cm. Planting density was determined based on the results of preliminary tests, which showed that the dense planting of more than 120 plants per square meter led to expected lodging in our region. Prior to basal fertilization, 100 g m⁻² of calcium carbonate was applied for soil amendment. The soil was then fertilized with 40 g m⁻² of nitrogen (N), 15 g m⁻² of phosphorous pentoxide (P₂O₅), and 10 g m⁻² of potassium oxide (K₂O), which is the standard application rate for common wheat in the Obihiro region.

To determine how the growth stage at defoliation, and harvest of the first crop, affect the yield and quality of both the first and second crops, the foliage was mowed at three different growth stages: booting stage, early-heading stage, and fully heading stage. Definitions of each growth stage in this study were as follows. Booting stage: the panicle in the sheath rises to just below the flag leaf but is not visible (Zadoks’ growth stage 45). Early-heading stage: approximately 30% of the plants developed initial panicles (Zadoks’ growth stage 53). Full-heading stage: all the plants have panicles but do not initiate anthesis (Zadoks’ growth stage 60) [21]. Plants mowed at the booting stage, early-heading stage, and fully heading stage were conveniently expressed as BT, EH, and FH, respectively. All the leaves and culms were mowed by hand using a sickle at a height of 15 cm above the soil level. After mowing, top-dressing of N was applied at a rate of 40 g m⁻² to promote regrowth. Plants grown conventionally for grain and left unmowed during their growth were used as the control. Grains were harvested from all plants at their mature stage. Threshed seeds were dried in a ventilating oven at 45 °C until they reached a water content of approximately 13%. The fields were designed by arranging the control, BT, EH, and FH in a randomized block design with 8 replicates for each year. Each plot was formed by five ridges of 6 m long (1 m × 6 m).

2.2. Measurements

Culm length, number of tillers, and dry matter (DM) yield were recorded for the first crop. Culm length was determined by measuring the distance from the soil level to the base of the flag leaf (BT) or the panicle base (EH and FH) of the tallest tiller on two randomly selected plants per plot. Harvested plant bodies were dried in the ventilating oven at 70 °C for 3 days and ground to a powder with an average particle size of 1 mm using a cyclone mill (CT293 Cyclotex^TM, FOSS, Hillleroed, Denmark) for nutritional analyses. Nutritional values such as ash content, organic cellular contents (OCC; non-structural sugars, proteins, starches, fat, etc., in cytoplasm), organic cell wall (OCW), organic a-fraction in OCW (Oa; cell wall digestible with cellulase), and organic b-fraction in OCW (Ob; cell wall indigestible with cellulase) were analyzed using the amylase/actinase/cellulase enzymatic method [22,23]. Total digestible nutrition (TDN) was estimated using the following equation developed by Abe et al. [24]:

TDN (%) = 1.111 (OCC + Oa) + 0.605 Ob − 18

Metabolizable energy (ME) was estimated using the following equation [25]:

ME (Mcal kg⁻¹ DM) = −1.849 + 0.0557 OCC + 0.0558 Oa + 0.0330 Ob

Then, the production of ME per unit area (MEP) was predicted by multiplying the ME and DM yield.

At the time of the final harvest, the culm length and number of tillers were recorded again in each plot. The regrowth rate was calculated for the dual-cropped plots using the following equation:

$$\mathrm{R}\mathrm{e}\mathrm{g}\mathrm{r}\mathrm{o}\mathrm{w}\mathrm{t}\mathrm{h} \mathrm{r}\mathrm{a}\mathrm{t}\mathrm{e}\left(\mathrm{\%}\right)=\frac{\mathrm{N}\mathrm{o}.\mathrm{t}\mathrm{i}\mathrm{l}\mathrm{l}\mathrm{e}\mathrm{r}\mathrm{s} \mathrm{a}\mathrm{t} \mathrm{t}\mathrm{h}\mathrm{e} \mathrm{s}\mathrm{e}\mathrm{c}\mathrm{o}\mathrm{n}\mathrm{d} \mathrm{c}\mathrm{r}\mathrm{o}\mathrm{p}}{\mathrm{N}\mathrm{o}.\mathrm{o}\mathrm{f} \mathrm{t}\mathrm{i}\mathrm{l}\mathrm{l}\mathrm{e}\mathrm{r}\mathrm{s} \mathrm{a}\mathrm{t} \mathrm{t}\mathrm{h}\mathrm{e} \mathrm{f}\mathrm{i}\mathrm{r}\mathrm{s}\mathrm{t} \mathrm{c}\mathrm{r}\mathrm{o}\mathrm{p}}\times 100$$

Threshed and dried seeds were screened using a sieve with a mesh size of 2.2 mm. Then, the seeds that remained on the sieve were used to measure grain yield, 1000 grain weight, and protein content. Protein content was estimated using a near-infrared transmittance grain analyzer (Infratec^TM 1241, FOSS, Hillleroed, Denmark).

2.3. Statistical Analysis

To ensure a normal distribution and equal variance, an arcsine transformation was applied to the nutrient data of the first crops [26]. All data were analyzed using a two-way analysis of variance (ANOVA), with years and harvest time of the first crop as the main variable factors. In the absence of interaction or random block effects, the variances were combined with the total error variance, and the effects of the main factors were retested. When significant effects of the main factors were detected, the Bonferroni post hoc comparison test was performed to compare the means between plants or years at the 5% level. The statistical software package SPSS ver. 22^TM (IBM Corporation, Armonk, NY, USA) was used for analyses.

3. Results

3.1. Weather Condition of Two Experimental Periods

The climate record, taken by a data logger (ATOMOS41/ZL6^TM, METER Group, Pullman, WA, USA) set at the experimental field, indicated that the daily average temperature, effective accumulative temperature, and cumulative precipitation during the sowing period until to the beginning of continuous snow cover (30 September to 15 December) were 5.8 °C, 241.2 °C, and 195.5 mm in 2018, and 5.2 °C, 222.3 °C, and 207.5 mm in 2019, respectively. In both years, the weather conditions before snowfall were similar, and the plants developed a comparable number of leaves and tillers in the first week of December. During the snow melting period until the final harvest began (1 April to 15 August), the daily average temperature and effective accumulative temperature did not differ significantly between the two years (15.1 °C and 1454.3 °C in 2019; 14.9 °C and 1422.3 °C in 2020). However, in 2020, there was a period of hot weather, with temperatures above 25 °C, that lasted for several consecutive days at the end of July. This caused the second crop to burn up prematurely. The period from late June to mid-July in 2020, when the second crops were in the panicle emergence stage, was characterized by low precipitation, approximately half of the normal amount for that time of year.

3.2. Growth and Yield of the First Crop

Harvest day, culm length, number of tillers, and DM yield in the first crop are shown in

Table 1. Harvest date and means of culm length, number of tillers and dry matter (DM) yield in the first crop of the dual-purpose cropping rye.

Year	Treatment	Harvest Date	Culm Length (cm)	No. of Tillers (m−2)	DM Yield (g m−2)
2018/2019	BT	20 May	82.7 c	844	518 c
	EH	26 May	100.1 b	817	698 b
	FH	31 May	108.5 a	798	754 a
2019/2020	BT	24 May	78.5 n	761	442 n
	EH	30 May	101.7 m	751	638 m
	FH	4 June	115.1 l	698	759 l
Total	2018/2019		97.2	820 p	656 p
	2019/2020		98.4	737 q	613 q
	BT		80.7 z	802	480 z
	EH		100.9 y	784	668 y
	FH		111.8 x	748	757 x
ANOVA	Year		ns	**	**
	Treatment		**	ns	**
	Interaction		**	ns	ns

Values followed by different letters within columns of same year or same treatment are significantly different at p = 0.05 according to Bonferroni post hoc comparison test. ns = not-significant; ** = significant at p = 0.01.

. In both years, the first crops were harvested sequentially from late May at five- or six-day intervals. Along with the growth stage, the plants grew taller, and the average culm length over two years was longer in the following order: FH (111.8 cm), EH (100.9 cm), and BT (80.7 cm). Many of the vegetative tillers in rye senesced and disappeared after the booting stage. The number of tillers tended to decrease as the growth stage progressed, although the differences between plants in both years were not statistically significant. The first crop that was harvested in the later growth stage had a higher DM yield. The highest DM yield (757 g m⁻²) was observed in FH, which was 1.5 times higher than that in BT (480 g m⁻²). The number of tillers and DM yield were higher in 2018/2019 than in 2019/2020. The earlier spring thaw in 2019 may be one reason for these results.

3.3. Nutritional Values of the First Crop

Nutritional values of the first crops obtained through enzymatic analysis are presented in

Table 2. Nutritional values and metabolizable energy production in the first crop of dual-purpose cropping rye.

				OCW (%)				MEP
Year	Treatment	Ash (%)	OCC (%)	Oa	Ob	Oa + Ob	TDN (%)	(Mcal m−2)
	BT	9.0 a	34.6 a	16.1 a	40.3 c	56.5 c	61.9 a	1.19 b
2018/2019	EH	8.5 a	29.9 a	11.8 ab	49.8 b	61.6 b	57.6 b	1.52 a
	FH	7.7 b	23.6 b	11.1 b	57.7 a	68.8 a	54.6 c	1.48 a
	BT	9.6 l	38.1 l	17.8 l	34.5 n	52.3 c	64.2 l	1.28 m
2019/2020	EH	8.9 m	28.9 m	16.2 l	46.0 m	62.2 b	59.2 m	1.49 l
	FH	8.2 n	23.4 n	12.7 m	55.7 l	68.4 a	55.0 n	1.52 l
Total	2018/2019	8.4 q	29.3	13.0 q	49.3 p	62.3	58.1	1.43
	2019/2020	8.9 p	30.2	15.6 p	45.4 q	61.0	59.2	1.40
	BT	9.3 x	36.4 x	17.0 x	37.4 z	54.4 z	63.1 x	1.24 y
	EH	8.7 y	29.4 y	14.0 y	47.9 y	61.9 y	58.4 y	1.51 x
	FH	7.9 z	23.5 z	11.9 z	56.7 x	68.6 x	54.8 z	1.50 x
ANOVA	Year	**	ns	**	**	ns	ns	ns
	Treatment	**	**	**	**	**	**	**
	Interaction	ns	ns	ns	ns	ns	ns	ns

Values followed by different letters within columns of same year or same treatment are significantly different at p = 0.05 according to Bonferroni post hoc comparison test. ns = not-significant; ** = significant at p = 0.01. OCC = Organic cellular contents; OCW = Organic cell wall; Oa = Organic a-fraction in OCW; Ob = Organic b-fraction in OCW; TDN = Total digestible nutrition; MEP = Metabolizable energy production per unit area.

. In both years, OCC, the aggregation of soluble organic matter in the cell was higher in plants harvested at earlier stages. The average OCC over two years in BT was 36.4%, which is more than 10 percentage points higher than that in FH (23.5%). On the contrary, the total OCW (Oa + Ob) increased during the growth stage. Among the components of OCW, the proportion of the indigestible fraction, Ob, changed as it grew and increased in the following order: BT (37.4%), EH (47.9%), and FH (56.7%). A higher TDN was recorded in plants harvested at earlier stages, with the highest value being 63.1% in BT. On the other hand, EH (1.51 Mcal m⁻²) and FH (1.50 Mcal m⁻²), which showed the higher dry matter production, achieved a higher MEP.

3.4. Growth of the Second Crop and Grain Yield

In both years, the control was harvested on 28 July. Approximately two weeks later, the plants in the dual-cropped plots reached maturity and were harvested together on 12 August 2019 and 11 August 2020, respectively. The culm length, number of tillers, and regrowth rate are shown in

Table 3. Means of culm length and number of tillers at the final harvest, and regrowth rate in the second crop of dual-purpose cropping rye.

Year	Treatment	Culm Length (cm)	No. of Tillers (m−2)	Regrowth Rate (%)
	Control	143.1 a	875 a	-
2018/2019	BT	131.6 b	485 b	57.5 a
	EH	128.6 b	430 c	52.6 b
	FH	120.9 c	339 d	42.4 c
	Control	172.6 l	766 l	-
2019/2020	BT	132.6 m	433 m	57.5 l
	EH	120.7 n	335 n	44.6 m
	FH	117.2 n	288 o	41.3 n
Total	2018/2019	131.2 q	532 p	50.8 p
	2019/2020	135.7 p	455 q	47.6 q
	Control	157.9 w	821 w	-
	BT	132.1 x	459 x	57.2 x
	EH	124.7 y	382 y	48.6 y
	FH	119.4 z	313 z	41.8 z
ANOVA	Year	**	**	*
	Treatment	**	**	**
	Interaction	*	ns	ns

Values followed by different letters within columns of same year or same treatment are significantly different at p = 0.05 according to Bonferroni post hoc comparison test. ns = not-significant; * = significant at p = 0.05; ** = significant at p = 0.01.

. All plants in the dual-cropped plots were smaller than those in the control at the mature stage. The average culm length of the second crop ranged from 119.4 cm (FH) to 132.1 cm (BT) over 2 years, which was significantly shorter than that of the control (157.9 cm). The number of tillers in the second crop ranged from 313 m⁻² (FH) to 459 m⁻² (BT), which was also lower than that in the control (821 m⁻²). Good regrowth was observed in plants that were defoliated at earlier stages. BT exhibited the highest regrowth rate, averaging 57.2% over two years, and produced a second crop with more tillers compared to EH and FH.

The grain yield was significantly lower in the second crops than in the control (411 g m⁻²,

Table 4. Means of grain yield, 1000 grain weight and protein content at the final harvest.

Year	Treatment	Grain Yield (g m−2)	1000 Grain Weight (g)	Protein Content (mg g−1)
	Control	407 a	48.1 a	119.1 b
2018/2019	BT	283 b	33.5 b	118.8 b
	EH	141 c	29.8 c	123.4 a
	FH	78 d	26.9 d	125.3 a
	Control	416 l	50.8 l	125.7 n
2019/2020	BT	195 m	31.4 m	127.2 mn
	EH	124 n	28.7 n	130.0 m
	FH	74 o	27.4 o	141.7 l
Total	2018/2019	227 p	34.6	121.6 q
	2019/2020	202 q	34.6	131.2 p
	Control	411 w	49.5 w	1224 z
	BT	239 x	32.4 x	123.0 z
	EH	132 y	29.2 y	126.7 y
	FH	76 z	27.2 z	133.5 x
ANOVA	Year	*	ns	**
	Treatment	**	ns	**
	Interaction	ns	**	**

Values followed by different letters within columns of same year or same treatment are significantly different at p = 0.05 according to Bonferroni post hoc comparison test. ns = not-significant; * = significant at p = 0.05; ** = significant at p = 0.01.

). Among the second crops, BT showed the highest grain yield of 239 g m⁻² over two years, which corresponded to 60% of the control. On the other hand, FH produced grains of only 76 g m⁻² on the regenerated plants, which was less than 20% of the control. On average, the 1000 grain weight in the second crops ranged from 27.2 g (FH) to 32.4 g (BT) over two years, which was also lower than the control (49.5 g; Table 4). The protein content of the grains was the lowest in the control (122.4 mg g⁻¹) and BT (123.0 mg g⁻¹). Among the second crops, the protein content was higher in plants where the first crop had been mowed at a later stage.

4. Discussion

The dual-purpose cropping system enables the production of both roughage and concentrate during a single growing season. From an economic standpoint, farmers could potentially earn two sources of income by cultivating a single crop species. Double-cropping system is another promising strategy for producing both roughage and concentrate within a year [27,28,29]. This system involves growing two different crops consecutively on the same field, such as winter cereal and maize or sorghum. A double-cropping system can achieve higher biomass yields compared to the single cropping of respective crops and also establish diversification of the feed produced. However, farmers would have to invest additional time and labor for plowing and seeding twice a year [27]. A dual-purpose cropping system, where roughage and concentrate can be obtained from a single plant, is considered to be more efficient in terms of labor savings [30].

Many of the gramineous plants, including forage grasses and cereals, undergo vertical growth after panicle formation and reach their maximum height during the flowering stage [31,32,33]. Therefore, foliage mass will increase during the flowering stage [34,35]. In the case of timothy, a major temperate forage grass in the Hokkaido area, the dry matter weight of the aboveground body increases by as much as 1.5 times from the booting stage to the full-heading or flowering stage [36,37,38]. Rye also grew taller and produced more foliage as it continued to grow. In the results of this study, the crop growth rate during the booting stage to full-heading stage was calculated to be a high value of 25.1 g m⁻² day⁻¹, averaged over two years. The dry matter (DM) yield of the first crop increased by approximately 1.4 times during the 6-day period from the booting stage to the early-heading stage. It then increased by about 1.1 times during the 5-day period from the early-heading stage to the full-heading stage. In terms of yield, the full-heading stage was determined to be the appropriate time to harvest the first crop among the growth stages defined in this study.

The productivity of forage crops must be measured not only by weight but also by the amount of nutrients produced [39,40]. Common forage grasses tend to decline in nutritional value and rumen digestibility as the panicles emerge from the sheath. This is because nutrient components, such as soluble carbohydrates and proteins, are transferred to the reproductive organs, which become stiff and indigestible [34,38,41]. Festulolium, a temperate perennial forage, exhibited a decrease in the quantity of organic cell content or cellulase digestible fiber in the foliage after panicle emergence. Instead, it rapidly increased the amount of non-digestible fiber. Aa a result, the total digestible nutrients (TDN) at the full-heading stage were approximately 5 percentage points lower compared to the booting stage [42]. Similarly, as the rye grew, the nutritive components (OCC and Oa) decreased sharply, while the non-nutritive component (Ob) increased. As a result, TDN was approximately 9 percentage points lower in FH compared to BT. The translocation of nutrient components to reproductive organs was enhanced during panicle emergence [38,43], and this physiological process was more prominent in annual cereals, such as rye, than in perennial grasses [35,44,45]. Delaying harvesting until the heading stage resulted in a greater yield of herbage, but it also decreased the nutritional quality as roughage. Nevertheless, EH and FH produced a higher metabolic energy per unit area compared to BT. The decline in nutritional value observed in the first crop was compensated for by the increase in yield. In terms of nutrient production, the early-heading stage or the full-heading stage was determined to be the appropriate time to harvest the first crop, as defined in this study.

After the onset of reproductive growth, grass plants generally show improved regrowth when their foliage is harvested at an earlier stage. During this stage, a substantial amount of the nutrients are retained in the stubble and roots [46,47,48], while the relationship between the time of defoliation and the vigor of regrowth is obscure in winter cereals during the tillering stage [14,49,50]. In this study, defoliation was applied during the reproductive growth stage, and the plants that were mowed earlier exhibited vigorous regrowth. As evidenced by the changes in the nutrient values of the first crops, BT preserved a larger proportion of the nutrients in the vegetative organs compared to EH and FH. This led to an ample supply of resources for vigorous regrowth. However, regardless of the timing of defoliation, the size of the second crop was significantly smaller than that of the control.

Previous studies on dual-purpose cropping systems of cereals, which assumed that the foliage was used for grazing at the tillering stage, reported that the body mass and grain productivity of the second crop were comparable to those of the non-grazed control [14,51,52]. In this study, however, even though BT showed the better regrowth ability compared to the other dual-cropped plants, it yielded significantly less grain than the control. The impact of defoliation may be more significant if plants experience defoliation during the reproductive stage compared to the vegetative growth stage. As for FH, the grain yield was too low to meet the objective of the dual-purpose cropping system, which aims to produce grain in the second crop. In order to practice the dual-purpose cropping of rye, the first crop must be harvested at least until the early-heading stage. Compared to the control and BT, EH had a higher protein content in the grains. Given the smaller grain size of EH, the lower translocation of carbohydrates into the grain can be attributed to the higher protein content expressed as w/w, rather than an increase in protein production [14,53]. Further investigation is needed to determine the quality of EH’s grain as a starch resource concentrate. Based on the quantity and quality of the grains of the second crop, the appropriate time for harvesting the first crop, as defined in this study was considered to be the booting stage.

5. Conclusions

This study demonstrated the feasibility of the dual-purpose cropping of rye, even when the foliage was mowed during the reproductive growth stage. However, a five-day delay in defoliation resulted in a significant difference in the yield and quality of the first crop, as well as in the regrowth and grain production of the second crop. In order to establish a dual-purpose cultivation system that utilizes foliage for mowing, it is necessary to harvest the first crop before it reaches the full heading stage. If farmers prioritize roughage production, the most preferable period for harvesting the first crop, among the growth stages examined in this study, would be the early-heading stage in terms of the higher TDN and MEP yields. On the other hand, if the priority is given to concentrate production (grain), it is preferable to harvest the first crop at the booting stage when higher regrowth ability and grain yield can be expected.