Sweet Pearl Millet Research Articles

Sweet Sorghum And Sweet Pearl Millet Carbohydrate Extraction and Preservation for Bioethanol Production and Bagasse Valorization: A Review

Highlights Sweet sorghum and sweet pearl millet are interesting feedstocks for ethanol production. Biomass and juice storage are key steps for carbohydrate preservation. Produced bagasse can be valorized in many ways, including as silage or for cellulosic ethanol production. Abstract. Sweet sorghum and sweet pearl millet have been considered as potential energy crops. They have many advantages in terms of ethanol production compared to corn and sugarcane, such as lower requirements for water and fertilizers, higher tolerance to drought, and lower competition with the food sector. Sweet sorghum and sweet pearl millet stems are rich in water-soluble carbohydrates (WSC) (sucrose, fructose, and glucose), and their biomass has to be crushed for juice extraction. However, the extraction efficiency of WSC varied widely depending on the press type used and the parameters considered during the pressing process (stripping stems from leaves or not, compressive force magnitude, smooth or grooved press rollers, number of times of biomass pressing, etc.). WSCs are easily degradable, causing technical challenges related to crop handling before pressing and juice storage thereafter. Some studies focused on stem preserving methods, whereas others dealt with extending the shelf life of the juice. To make the use of sweet sorghum and sweet pearl millet as energy crops more profitable, the bagasse (residue) generated from biomass pressing can be valorized in different ways, mainly as silage or for second generation ethanol production. The objective of this review was to assess the efficiency of different presses used for juice extraction and discuss various methods tested for WSC conservation from deterioration as well as possible bagasse valorization. Keywords: Bagasse, Carbohydrates, Ethanol, Press, Sweet pearl millet, Sweet sorghum.

Ensilability and Nutritive Value of Sweet Sorghum and Sweet Pearl Millet Bagasse as Affected by Different Methods of Carbohydrate Extraction for Eventual Ethanol Production

HighlightsJuice extraction resulted in a decrease in the nutritive value of the bagasse as compared with the initial biomass.Silages made from the second pressing bagasse were well conserved.Sweet sorghum silage has a better nutritive value than sweet pearl millet.Abstract. Pressing the biomass of sweet sorghum and sweet pearl millet in-field is one of the suggested options for bioethanol production. The extracted juice can be delivered to an ethanol plant, and the bagasse (pressing residue) can be used for ruminant feeding. Efficient carbohydrate extraction is highly important for good ethanol yield. However, enough carbohydrates must remain in the bagasse for its adequate conservation as silage. In this study, the ensilability and the chemical composition of the second pressing bagasse of sweet sorghum and sweet pearl millet were investigated. The bagasse was obtained following a second pressing of the first pressing bagasse after its impregnation with water based on three water:bagasse ratios (0.5, 1, and 1.5). Results indicated that water:bagasse ratio did not affect water-soluble carbohydrate (WSC) extraction for both crops. The second pressing bagasse of sweet sorghum and sweet pearl millet contained 80.5 ±4.6 and 60 ±4.6 g of WSC kg-1 dry matter (DM), respectively. The second pressing bagasse of both crops had reduced nutritive value compared to the initial biomass, i.e., higher neutral detergent fiber (NDF) and acid detergent fiber (ADF) concentrations along with lower non-structural carbohydrate (NSC) concentration, in vitro true digestibility of DM (IVTD), and in vitro NDF digestibility (NDFd). The second pressing bagasses of both crops also showed good ensilability, but sweet sorghum bagasse silages were of better nutritive value than sweet pearl millet bagasse silages (ADF = 446.2 ±3.7 vs. 463.2 ±3.7 g kg-1 DM, IVTD = 813.8 ±3.4 vs. 708.8 ±6.8 g kg-1 DM, and NDFd = 741.8 ±4.8 vs. 596.2 ±8.5 g kg-1 NDF, respectively). The water:bagasse ratio used for bagasse impregnation before the second pressing only affected the NDF concentration of silages, as a higher NDF concentration was obtained with a water:bagasse ratio of 1.5. Sweet sorghum and sweet pearl millet can be considered dual-purpose crops; the extracted juice can be fermented into ethanol, and the second pressing bagasse can be used to make good-quality silage. Keywords: Bagasse impregnation, Nutritive value, Silage, Sweet pearl millet, Sweet sorghum, Water-soluble carbohydrates.

Optimization of Water-Soluble Carbohydrate Extraction from Sweet Sorghum and Sweet Pearl Millet Biomass

The interest for sweet sorghum and sweet pearl millet use as potential feedstocks for bioethanol production has markedly increased in the last few years due to the high concentration in fermentable carbohydrates in their juice. The bottleneck of this production is the carbohydrate extraction process that needs to be optimized. The main objective of this study was therefore to determine the effect of operating conditions on water-soluble carbohydrate (WSC) extraction from the biomass of both species. For this purpose, two chopping modes of the biomass (coarse and fine) were investigated. Furthermore, the biomass was subjected to a second pressing after impregnation with water. In this context, the effects of four water:bagasse ratios (0.5, 1, 1.5, and 2) and three water temperatures (25, 45, and 65 °C) were evaluated. The initial biomass WSC concentration was 180 g kg−1 DM for sweet sorghum and 125.7 g kg−1 DM for sweet pearl millet. After the first pressing, these concentrations decreased by 63 and 56%, respectively. For the second pressing, the efficiency of WSC extraction was more influenced by the water:bagasse ratio than by the chopping mode and the water temperature. For an economic and energetic sustainable extraction process of carbohydrates, a coarse chopping, and a second pressing after impregnation with a water:bagasse ratio of 1 at 25 °C are therefore recommended to improve residual carbohydrate extraction. Under these conditions, the WSC extraction yields reached 83 and 78% for sweet sorghum and sweet pearl millet biomass, respectively.

Forage yield, nutritive value, and ensilability of sweet pearl millet and sweet sorghum in five Canadian ecozones

Sweet pearl millet [Pennisetum glaucum (L.) R. Br.] and sweet sorghum [Sorghum bicolor (L.) Moench], previously tested for ethanol production, were evaluated as high sugar crops for animal feeds to possibly replace silage corn (Zea mays L.). We compared the forage yield, nutritive value, and ensilability of one hybrid of sweet pearl millet and two of sweet sorghum to a locally adapted silage corn hybrid in five Canadian ecozones. Forage yields of sweet pearl millet and sorghum were similar to that of silage corn in the Boreal Shield, Mixedwood Plain, and Atlantic Maritime ecozones, greater in the Prairies, and lower in the Pacific Maritime ecozone. Across sites, forage dry matter concentration was less for sweet pearl millet (289 g kg−1) and sweet sorghum (245 g kg−1) than for silage corn (331 g kg−1). Sweet pearl millet had a lower total digestible nutrient (TDN) concentration (452 g kg−1 DM) and aNDF digestibility (NDFd) than sweet sorghum and silage corn along with greater neutral detergent fibre (aNDF) and water-soluble carbohydrate (WSC) concentrations than silage corn. Sweet sorghum had greater aNDF and WSC, lower starch, and similar TDN (534 g kg−1 DM) concentrations, but greater NDFd compared with silage corn. Sweet pearl millet and sorghum fermented as well as silage corn, reaching low pH values and acceptable concentrations of lactic and volatile fatty acids. Sweet sorghum is therefore a viable alternative to silage corn in Canada except in the Pacific Maritime ecozone, but early-maturing hybrids with acceptable DM concentration at harvest are required.

Nutritive value of sweet pearl millet and sweet sorghum as influenced by N fertilization

Increasing N fertilization decreased the in vitro digestibility of dry matter (IVTD) and neutral detergent fiber (NDF) but increased N concentration of sweet sorghum [Sorghum bicolor (L.) Moench] and sweet pearl millet [Pennisetum glaucum (L.) R.Br.] in eastern Canada. Sweet sorghum had lower NDF, acid detergent fiber, and N concentrations, and greater IVTD than sweet pearl millet.

Water-Soluble Carbohydrate Extraction from Sweet Pearl Millet and Sweet Sorghum Biomass as Affected by Bagasse Impregnation

<abstract> <b><sc>Abstract.</sc></b> The extraction of the sugary juice from sweet sorghum and sweet pearl millet biomass is a major step for first-generation bioethanol production. However, an important amount of water-soluble carbohydrates (WSC) remains in the bagasse following a single pressing of the biomass in-field. Therefore, bagasse impregnation is required to collect residual carbohydrates. This study investigated the effects of bagasse impregnation liquid (water or juice from the first pressing of the biomass) and three impregnation durations (0, 30, or 60 min) for a second pressing on the WSC concentrations of the biomass, the bagasse, and the juice of sweet sorghum and sweet pearl millet. Our results showed that the impregnation duration had no effect on WSC concentration in the biomass, bagasse, and juice. However, water was more efficient than the first-pressing juice in extracting the residual WSC remaining in the biomass after the first pressing. The use of water for bagasse impregnation allowed extraction of a total of about 36% and 47.5% of WSC from sweet sorghum and sweet pearl millet biomass, respectively, compared to 28% and 41% when the first-pressing juice was used. Sweet sorghum and sweet pearl millet juice extracted from the biomass impregnated with water contained 21% and 28.5% more WSC, respectively, than the juice extracted from the biomass impregnated with the first-pressing juice. When pressing is carried out in-field, impregnation of the bagasse with water for a second pressing is highly recommended for more residual WSC extraction. However, the required quantity of water needs to be optimized.

Storage time effects on the soluble sugars concentration and pH of sweet pearl millet and sweet sorghum juice

Juice of sweet pearl millet and sweet sorghum can be extracted by mechanical pressing and then fermented to produce bioethanol. Since the juice contains a significant amount of soluble sugars, delays between the juice extraction and its transformation may be critical as sugars can degrade quickly. The main objective of this study was to determine the impact of storage time on sweet pearl millet and sweet sorghum juice pH and soluble sugars concentration. In 2013, the juice extracted from both crop species was stored at ambient temperature or under 4°C in a refrigerator up to 72 h. Juice was sampled every 24 h. In the 2014 experiment, the juice was stored at ambient temperature for 12 h and sampling was made after 0, 2, 4, 7, 8, 10, and 12 h. Obtained results showed that when the juice was refrigerated at 4oC, the pH and soluble sugars concentration remained stable throughout the 72 hours of storage. At ambient temperature, the total soluble sugars concentration significantly decreased during the first 24 h of storage of sweet sorghum juice (-17%) and between the first 24 to 48 h of sweet pearl millet juice (-29%). However, the total soluble sugars concentration did not vary in the juice of both crop species during the first 12 h of storage at ambient temperature. Producers have therefore up to a 12h-storage delay at ambient temperature after extraction before the need of a transformation process or the addition of preservation agents to avoid sugar degradation of the juice of both crop species.

Extraction of the Sugary Juice from Sweet Pearl Millet and Sweet Sorghum Using a Hydraulic Press and a Four-Roller Press

<abstract> <b><sc>Abstract.</sc></b> Sweet sorghum and sweet pearl millet have good agro-industrial potential because they can be used as energy crops, using the sugary juice contained in their stalks to produce bioethanol, while the bagasse (pressing residues) can be used as animal feed. However, the process of extracting the juice and consequently the sugar from the biomass of these crops needs to be explored. For this study, two experimental presses, a four-roller press and a hydraulic press, were designed and built at the Department of Soils and Agri-Food Engineering of Université Laval, in Quebec, Canada. With bioethanol production in mind, an experiment was carried out using the hydraulic press to investigate the effects of stalk chopping mode (fine vs. coarse) and various compressive forces, as well as a comparison between the two presses, to determine the more suitable press for extracting the sugary juice from these crops with or without leaves. The roller press gave good results with sweet sorghum, as no significant difference between the presses was found in the volume of juice extracted if the leaves were removed prior to extraction. However, the hydraulic press was more suitable than the roller press for extracting juice from sweet pearl millet. Chopping mode did not have any effect on the volume of juice extracted. Leaves should be removed prior to pressing with the roller press. When using the hydraulic press, leaf removal was necessary only with sweet sorghum. An estimated ethanol yield of 1956 L ha^-1 could be achieved using the hydraulic press to extract the juice from sweet sorghum without leaves.

Impact of Storage Time on the Juice and Sugars Extracted from Chopped and Whole Stalk Sweet Pearl Millet and Sweet Sorghum Biomass

Since they have a high concentrations of fermentable sugars, sweet pearl millet and sweet sorghum are two interesting crops for bioethanol production. However, if the juice is not extracted from the biomass immediately after harvest, the biomass has to be transported and stored for further juice extraction. This delay could affect the amount of juice extracted and its sugar concentration. This paper presents the results of 3 years of experiments where different storage modes (chopped and whole stalks) and various storage time (0 to 14 days) were applied on two different crop species (sweet pearl millet and sweet sorghum). Storing sweet pearl millet as whole stalks for 2 weeks resulted in a water-soluble carbohydrate (WSC) concentration decrease of 52 %, while no significant decrease of the WSC concentration was observed for sweet sorghum. Whole stalks storage is much more efficient than storing the biomass chopped to avoid a rapid sugar loss. However, more juice can be extracted from stored chopped biomass than from stored whole stalks biomass. If the juice cannot be extracted quickly after the harvest, the biomass can be stored as whole stalks to avoid rapid sugar deterioration, especially for sweet sorghum.

Root Traits and Carbon Input in Field‐Grown Sweet Pearl Millet, Sweet Sorghum, and Grain Corn

Little information exists on root morphological characteristics of agricultural crops under field conditions, which can be a major determinant of plant N uptake efficiency and C input to soil. Sweet pearl millet [Pennisetum glaucum (L.) R.BR.] and sweet sorghum [Sorghum bicolor (L.) Moench] are envisioned as energy crops in eastern Canada, to complement corn starch ethanol. The aims of this study were to characterize and compare root biomass and root traits of field‐grown sweet pearl millet, sweet sorghum, and grain corn (Zea mays L.), and to estimate their annual C input to soil. At two sites in eastern Canada, root samples recovered from 30‐cm deep soil cores in sandy loams were weighed and scanned. Image analysis was performed with the WinRhizo software. Roots and shoots were analyzed for C concentration. Estimated C input to soil at harvest was higher for corn (243 g C m−2) than for sorghum and millet (197 and 131 g C m−2, respectively). In contrast, millet and sorghum had the greatest specific root lengths (83, 39, and 22 m g−1 for millet, sorghum, and corn, respectively), and a larger contribution of very fine roots (&lt;0.5 mm diam.) to the total root surface (60–63% for millet and sorghum, and 45–55% for corn). The longer and finer roots of millet and sorghum could contribute to their high N uptake efficiency. However, compared to grain corn, their lower C input to soil needs to be recognized to ensure a balanced C budget.

Designing a prototype of press tool for the in-field pressing of sweet sorghum and sweet pearl millet biomass

Designing a prototype of press tool for the in-field pressing of sweet sorghum and sweet pearl millet biomass

Designing a prototype of press tool for the in-field pressing of sweet sorghum and sweet pearl millet biomass

Designing a prototype of press tool for the in-field pressing of sweet sorghum and sweet pearl millet biomass

Design and Testing of a Four-Roller Press to Extract Sugary Juice from Sweet Sorghum and Sweet Pearl Millet Biomass

<abstract> Sweet pearl millet and sweet sorghum have great potential for bioethanol production, because the sugary juice contained in their stalks can be extracted and eventually fermented to produce ethanol while the pressing residues can be used as livestock feed. However, the juice extraction process needs to be optimized. With a view to an in-field extraction process, a four-roller press was designed and built at the Department of Soils and Agri-Food Engineering of Université Laval, in Quebec, Canada. Three different roller speeds and one or two pressing runs were tested for extracting the juice from sweet pearl millet and sweet sorghum biomass. The results showed that the roller press might not be suitable for extracting the juice from sweet pearl millet, given the average moisture extraction of only 6.2% for that crop, in comparison with 24.6% for sweet sorghum. However, a slower roller speed, as well as multiple pressing runs, increased juice extraction by 51%. These two independent variables did not have any significant impact on the juice sugar concentration. With this specific roller press, it is therefore recommended to press the sweet sorghum biomass more than once at the slowest speed to extract the maximum amount of juice and therefore of sugar.

Sweet pearl millet and sweet sorghum have high nitrogen uptake efficiency under cool and wet climate

Nitrogen use efficiency is a key factor for the economic and environmental sustainability of farms. It comprises the ability for crops to recover applied fertilizer N in their aboveground biomass, called fertilizer N uptake efficiency (NupE). Sweet pearl millet (Pennisetum glaucum (L.) R.BR.) and sweet sorghum (Sorghum bicolor (L.) Moench) are C4 annual crops known for their capacity to produce high yield under N-limiting conditions, suggesting high NupE. A field study was conducted for 2 years on sandy loam soils in eastern Canada. The NupE was determined using a 15 N-tracing approach. Compar- isons were made for both species in regards to their response to (1) increasing mineral N rate (0-160 kg N ha -1 ), (2) mineral versus organic N (liquid swine and dairy cattle manures), and (3) single versus split N application. For mineral N treatments, NupE ranged from 54 to 82 %, which is greater than values generally reported for conventional crops such as corn. Moreover, NupE increased with N rates. These findings suggest than both species expressed N luxury consumption. The NupE was lower with organic than with mineral N, and a larger proportion of N remained in the soil, suggesting that N immo- bilization occurred. The presumed losses (unrecov- ered 15 N) were\24 kg N ha -1 in all mineral and most organic N treatments. Splitting N application had little effect on NupE. Our results confirm that sweet pearl millet and sweet sorghum are highly efficient at recovering fertilizer N and, with adequate residue management, may represent a low environmental risk.

Response to Nitrogen of Sweet Pearl Millet and Sweet Sorghum Grown for Ethanol in Eastern Canada

Sweet pearl millet [Pennisetum glaucum (L.) R.BR.] and sweet sorghum [Sorghum bicolor (L.) Moench] are considered for ethanol production in eastern Canada, but their response to N fertilization is not well established. Our objectives were (i) to compare both species for dry matter (DM), water-soluble carbohydrate (WSC), and estimated ethanol yields and (ii) to determine their response to mineral N rate (0, 40, 80, 120, and 160 kg N ha−1), (iii) mineral vs. organic N (liquid swine and dairy manures at 80 kg total N ha−1), and (iv) single vs. split N application (80 kg ha−1 mineral N). The two species were grown for 2 years on sandy loams in two ecozones (Mixedwood Plains [MWP] and Boreal Shield [BS]) with contrasting temperature regime. Both species responded similarly to mineral N fertilization, with maximum WSC yield at 86 kg N ha−1 at MWP and 91 kg N ha−1 at BS, and maximum DM yield at 121 kg N ha−1 at MWP and 107 kg N ha−1 at BS. Mineral N fertilization at 80 kg ha−1 resulted in higher DM and WSC yields than the manures, which showed fertilizer N equivalences varying from 15 to 52 %. Splitting mineral N rate between seeding and the four-leaf stage did not improve yield compared to a single application. Sweet sorghum had higher averaged WSC concentration and yield than sweet pearl millet (249 vs. 134 g WSC kg−1 DM; 3.41 vs. 2.02 Mg WSC ha−1) and appears more promising for ethanol production in eastern Canada.

Sugar Yield of Sweet Pearl Millet and Sweet Sorghum as Influenced by Harvest Dates and Delays Between Biomass Chopping and Pressing

Bagasse remaining after extracting the juice from crop biomass for ethanol production could be preserved as silage and used in animal feedstock, but the nutritive and conservation attributes of bagasse silage from sweet sorghum (Sorghum bicolor (L.) Moench) and sweet pearl millet (Pennisetum glaucum (L.) R.Br) are not well known. We evaluated the nutritive and conservation attributes of silages made with the bagasse of two species (sweet pearl millet and sweet sorghum) harvested on two dates (August and September) at two sites in Quebec (Canada) and ensiled after four delays between biomass chopping and pressing (0.5, 2, 4, and 6 h). Bagasse silages made in laboratory silos were considered well preserved (pH ≤ 4.0, NH3-N 30 g kg−1 DM, no propionic and butyric acids) regardless of species, harvest date, or delay between biomass chopping and pressing. Sweet pearl millet and sweet sorghum bagasse silages had similar total N concentration, in vitro true digestibility of dry matter (IVTD), and in vitro neutral detergent fiber digestibility (NDFD). Bagasse silage made from biomass harvested in August rather than in September had a 4 % greater concentration of total N, a 4 % greater IVTD, and a 8 % greater NDFD. The delay between biomass chopping and pressing did not affect the nutritive and conservation attributes of silages. Juice extraction from the biomass of sweet pearl millet and sweet sorghum did not impair attributes of good silage fermentation but it reduced its nutritive value.

Compressive Forces and Harvest Time Effects on Sugars and Juice Extracted from Sweet Pearl Millet and Sweet Sorghum

Abstract. In Canada, bioethanol is mainly produced from corn or wheat. Other alternative crops, such as sweet sorghum and sweet pearl millet, have been investigated in the province of QuA©bec, Canada, since they both have minimal fertilizer and water requirements. The objective of this study was to investigate the effects of compressive force and harvest time on the volume and sugar concentration of juice extracted from finely chopped biomass of sweet pearl millet and sweet sorghum. Trials using a specific screw press, both crop species, two harvest times, and three compressive forces were conducted at two experimental sites. Results showed that a compressive force between 310 and 379 kPa was adequate for juice extraction. Overall, a maximum of 632 mL juice kg -1 biomass was extracted from sweet sorghum, compared to 509 mL kg -1 from sweet pearl millet. The screw press succeeded in extracting 63.3% and 74.9% of the moisture from the biomass of sweet pearl millet and sweet sorghum, respectively. Compressive force had no effect on the sugar concentration of both crop juices. However, the juice extracted with the screw press contained large quantities of unwanted residues. Sugar concentration of the juice was greatest at one of the two sites when the biomass was harvested and compressed in the afternoon. However, the harvest time had no effect on juice extraction at either site. Sweet sorghum contained significantly more sugars than sweet pearl millet and tended to contain more sucrose than glucose and fructose. This study demonstrates that sweet sorghum and sweet pearl millet are good sources of fermentable sugars. However, further research is needed to refine the harvesting and juice extraction processes.

Sweet Pearl Millet Yields and Nutritive Value as Influenced by Fertilization and Harvest Dates

Sweet pearl millet [Pennisetum glaucum (L.) R.Br.] can be used for ethanol production from the extracted juice with residues used as livestock feed, but optimal fertilization and harvest dates are unknown for this “sugary stem” hybrid developed from forage pearl millet. We evaluated the effects of five equally spaced N fertilization rates (0–200 kg ha−1), K fertilization rates of 0 and 66 kg ha−1, and four harvest dates (approximately every 15 d from early or mid‐August in 2007 and 2008) on water soluble carbohydrate (WSC) concentration and yield, dry matter (DM) yield, and nutritive value of sweet pearl millet, at two sites with 2300 to 2500 and 2900 to 3100 crop heat units (CHU) in Québec, Canada. Delaying harvest dates increased DM (22–99%) and WSC yields (98–173%), and WSC concentration but decreased N concentration by 36% and neutral detergent fiber digestibility (dNDF) by 19%. Increasing N fertilization increased DM and WSC yields, and N concentration, but had no effects on WSC concentration, and decreased dNDF moderately. Potassium fertilization had limited effects on DM and WSC yields, WSC concentration, and on most attributes of nutritive value. Fertilization with 78 to 90 kg N ha−1 and an accumulation of 2100 to 2200 CHU corresponding to harvest dates in September are required to maximize WSC yield (1.86–2.83 Mg ha−1) of sweet pearl millet in eastern Canada. Maximizing WSC yield with the goal of producing ethanol, however, would result in reduced nutritive value.

Yield and Composition of Sweet Pearl Millet as Affected by Row Spacing and Seeding Rate

Sweet pearl millet [Pennisetum glaucum (L.) R. BR.] seems promising for ethanol production, but optimal cropping practices are unknown for the cool and humid conditions of eastern Canada. We evaluated the effects of two row spacings (18 and 36 cm) and four seeding rates (5, 10, 15, and 20 kg ha−1) on biomass dry matter (DM) yield, water soluble carbohydrate (WSC) concentration and yield, and nutritive value of sweet pearl millet at two sites in Québec, Canada. Increasing seeding rates decreased biomass DM and WSC yields at Sainte‐Anne‐de‐Bellevue but had a limited effect at Saint‐Augustin‐de‐Desmaures. Hence, a seeding rate of 5 kg ha−1 resulted in maximum biomass DM (12.4–19.1 Mg ha−1) and WSC (1.56–2.64 Mg ha−1) yields. Row spacing did not affect biomass DM and WSC yields at Saint‐Augustin‐de‐Desmaures but biomass DM yield was greater at a row spacing of 18 cm at Sainte‐Anne‐de‐Bellevue. The WSC concentrations in leaves and stems were inconsistently affected by seeding rate but were not affected by row spacing. The WSC concentrations were greater in stems (140.7–162.4 g kg−1 DM) than in leaves (35.7–48.1 g kg−1 DM). Increasing the seeding rate generally decreased N concentrations of leaves and stems and digestibility of neutral detergent fiber (NDF) but increased concentrations of acid detergent fiber and NDF. Row spacing did not affect any nutritive value attributes. Seeding at 5 kg ha−1 with a row spacing of 18 cm maximize biomass and WSC yield with minimal effect on forage nutritive value of sweet pearl millet.

SELECTION OF SUPERIOR SWEET PEARL MILLET FODDER TYPES BY HETEROSIS

Superior fodder sweet pearl millet types were selected by heterosis study from 76 crosses (crossing 4 lines and 19 testers in a L x T mating design). The cross 843 A x L 90 is the earliest fodder type and the cross 732 A x VVJ 2 is considered to be the best for the straw yield. The cross LII Ax L90 is considered to be the best sweet type as it recorded the highest total soluble solids value.