Growth and development of tomato se

Growth and development of tomato seedlings in sphagnum peat, vermiculite, and processed rice hull substrates
Matthew K. Nutt* and Michael R. Evans^
ABSTRACT
Tomato (Lycopersicum esculentum ‘Early Girl’) seedling growth was evaluated in substrates con¬taining varying proportions of ground rice hulls. Substrates were formulated containing 0, 30, 60, and 90% ground rice hulls with one-half of the treatments also treated with a surfactant. Seedling growth in two of the ground rice hull-containing substrates was generally similar to the two controls of 90% peat or 100% vermiculite. The germination percentages for all ground rice hull-containing substrates were similar to the two controls. Ground rice hulls are a viable alter¬native to peat and vermiculite seedling substrates.
Matthew K. Nutt is a senior majoring in horticultural science.
^ Michael R. Evans, faculty mentor, is an associate professor in the Department of Horticulture.

INTRODUCTION
Artificial substrates are most commonly used in greenhouse crop production (Nelson, 1998). These sub¬strates are made of various components blended in vary¬ing proportions to produce a substrate with physical and chemical properties suitable for its intended use (Blunt, 1988). These components may be naturally occurring, man-made, or a municipal or agricultural by-product. One of the commonly used natural components is Sphagnum peat (peat). Sphagnum peat is generally used in artificial substrates for its water- and nutrient-holding capacity. However, significant interest has been expressed in finding alternatives to peat due to environmental con¬cerns (Barkham, 1993; Buckland, 1993; Robertson, 1993) and costs associated with this component.
Some research has been completed in the use of municipal waste products such as waste paper products (Chong and Cline, 1993; Norrie and Gosselin, 1996), composted yard waste (Beeson, 1996), and municipal sewage sludge (Mori et al., 1981) as alternatives to peat. Additional research has been conducted on industrial and agricultural waste products. Some of these include coconut coir (Evans and Stamps, 1996), composted rice
hulls (Laiche and Nash, 1990), processed poultry feath¬ers (Evans, 2004), kenaf (Wang, 1994), and composted animal manures (Tyler et al., 1993).
Many of these alternative substrates were discarded due to their chemical or physical properties not meeting the needed properties for the substrate mix as used by the industry. Additionally, expense eliminated or great¬ly slowed others, such as ground bovine bone as a replacement for perlite (Evans, 2004).
Rice hulls are a by-product of the rice milling indus¬try in Arkansas and across the United States. It has been estimated that 31 million metric tons of fresh rice hulls are produced annually in the United States (Kamath and Proctor, 1998).
Fresh rice hulls have not been used in potting sub¬strates in the past because it was believed they caused nitrogen depletion. However, it was recently found that nitrogen depletion did not occur to any significant extent (Evans and Gachukia, 2004) when fresh rice hulls are used as a component in substrates. Furthermore, rice seeds have been a common contaminant of rice hulls and, therefore, created a weed problem (Evans and Gachukia, 2004). However, parboiled rice hulls were found to be free of viable weed seeds (Evans and Gachukia, 2004). 
All previous research conducted with rice hulls has replaced perlite and used whole parboiled fresh rice hulls to provide for drainage and air-filled pore space. Substrate particle size directly affects pore size. Large particles create large pores that drain and become air- filled after irrigation. Small particles create small pores that retain water for use by the plant. By grinding rice hulls, the particle size is reduced. The smaller-sized rice hull particles should create small pores that hold water. Thus, ground rice hulls (GRH) might be used as an alternative to peat. Further, grinding destroys any viable rice seed eliminating the weed problem and allowing for the use of non-parboiled hulls.
Surfactants are used in the horticultural industry to increase the water-holding capacity of substrates. These surfactants are used on many alternative substrates to increase water-holding capacity. Their use might allow for the use of other alternative substrates which might not otherwise be useful due to low water-holding capac¬ity. Ground rice hulls may not provide sufficient water¬holding capacity and therefore may require that a surfac¬tant be added to increase water-holding capacity.
The objective of this research was to determine if ground rice hull products could be used as an alternative to peat in the production of seedlings.
MATERIALS AND METHODS
Rice hulls were acquired from Riceland Foods (Stuttgart, Ark.) and ground in a Wiley Hammer Mill (Arthur H. Thomas Co., Philadelphia, Penn.). This process created a product in which 98% of the particles were less than or equal to 2.0 mm in size (Fig. 1). The ground rice hulls (GRH) either remained untreated or were treated with the surfactant Soax (Scotts, Marysville, Ohio) at the recommended label rate.
Substrates were formulated by blending the GRH, peat, and perlite (4 to 6 mm). All substrates contained 10% per¬lite and 30, 60, or 90% GRH with the remainder being peat. Calcitic limestone was added to the peat to adjust its pH to approximately 5.5. Two control treatments were evaluated. One control consisted of 90% peat and 10% perlite with no surfactant. An additional control substrate of 100% vermiculite was also included.
Substrates were placed into five-cell-by-five-cell mini-plug trays, made from round #273 (5 ml volume per plug cell) plug trays. One tomato seed (‘Early Girl’) was plant¬ed per cell. Plug trays were then transferred to a bi-wall polycarbonate-glazed greenhouse. The low-temperature set point was 18°C. Light levels averaged 250 |^mol . sec-1 . m-2 at 12 h. The trays of substrates were misted once or twice daily to ensure a constantly moist substrate required for germination. All trays were misted at the same time, thus applying the same amount of water to all substrates. The mini-plug trays were fertilized with a 25 mg . L-1 nitro¬gen solution using N-P-K 15-5-15 Excel (Scotts, Marysville, Ohio) with every misting from the start of the third week until the experiment was terminated at the end of the fifth week. There were eight treatments with three replications, with a tray being a replication. The replica¬tions were placed on the greenhouse bench in a random pattern.
An analysis of variance was run to establish if there were significant differences in seedling germination and growth among the different substrates. A least significant difference mean separation test (a = 0.05) was used to ascertain which means were significantly different.
RESULTS AND DISCUSSION
Seedlings grown in vermiculite had higher per-tray fresh shoot weights than seedlings grown in all other sub¬strates (Table 1). Seedlings grown in the 90% GRH with¬out surfactant and 60% GRH with surfactant had similar fresh shoot weights as the 90% peat substrate. All other GRH-containing substrates had lower fresh shoot weights than the 90% peat control.
Vermiculite, 90% GRH without surfactant, and 90% peat all had similar per-tray fresh root weights (Table 1). The 30% GRH with surfactant, 60% GRH without surfac¬tant, and 90% GRH with surfactant had lower fresh root weights per tray than the 90% peat control.
Seedlings grown in 90% GRH without surfactant, 60% GRH with surfactant, 90% peat, and 100% vermicu¬lite all had similar dry shoot weights. The 90% GRH with surfactant, 60% GRH without surfactant, and 30% GRH with surfactant had similar dry shoot weights per tray but were significantly lower than the controls. All seedlings had similar per-tray dry root weights regardless of the substrate. The germination percentage was similar for all substrates except the 30% GRH with surfactant, which was significantly lower than the 90% peat or 100% ver¬miculite controls.
Fresh shoot weights per plant for vermiculite and 90% GRH without surfactant were similar (Table 2). The fresh shoot weights per plant were similar for seedlings grown in 90% peat, 90% GRH without surfactant, and 60% GRH with surfactant. However, the 90% peat and 60% GRH with surfactant were significantly lower than ver¬miculite. Seedlings grown in 30% GRH-without-surfac- tant, 60% GRH-without-surfactant, 30% GRH-with-sur- factant, and 90% GRH-with-surfactant substrates had lower per-plant fresh shoot weights than those grown in the 90% peat and vermiculite controls (Table 2).
The average fresh root-weights per plant for seedlings grown in the two controls of 90% peat or 100% vermicu- lite were similar to the 90% GRH without surfactant. All other seedlings grown in GRH-containing substrates had similar average fresh root-weights per plant and were sig¬nificantly

Kết quả (Việt) 1:

Tăng trưởng và phát triển của cà chua cây giống giống rong thủy đài than bùn, vermiculite và chế biến gạo thân chấtMatthew K. Nutt * và Michael R. Evans ^TÓM TẮTSự phát triển cây giống cà chua (Lycopersicum dớn 'Đầu cô gái') được đánh giá trong con¬taining chất nền khác nhau tỷ lệ đất gạo vỏ. Chất nền đã được xây dựng có chứa 0, 30, 60, và 90% đất gạo vỏ với một nửa của phương pháp điều trị cũng được điều trị bằng một chất. Cây giống tăng trưởng năm hai trong đất gạo thân có chứa chất là thường tương tự như các điều khiển hai của 90% than bùn hay 100% vermiculite. Tỷ lệ nảy mầm cho tất cả đất gạo thân có chứa chất được tương tự như các điều khiển hai. Đất gạo vỏ là một alter¬native khả thi để than bùn và vermiculite cây giống chất nền.Matthew K. Nutt là một cấp cao majoring trong khoa học làm vườn.^ Michael R. Evans, cố vấn khoa, là một phó giáo sư trong vùng rau quả. GIỚI THIỆUArtificial substrates are most commonly used in greenhouse crop production (Nelson, 1998). These sub¬strates are made of various components blended in vary¬ing proportions to produce a substrate with physical and chemical properties suitable for its intended use (Blunt, 1988). These components may be naturally occurring, man-made, or a municipal or agricultural by-product. One of the commonly used natural components is Sphagnum peat (peat). Sphagnum peat is generally used in artificial substrates for its water- and nutrient-holding capacity. However, significant interest has been expressed in finding alternatives to peat due to environmental con¬cerns (Barkham, 1993; Buckland, 1993; Robertson, 1993) and costs associated with this component.Some research has been completed in the use of municipal waste products such as waste paper products (Chong and Cline, 1993; Norrie and Gosselin, 1996), composted yard waste (Beeson, 1996), and municipal sewage sludge (Mori et al., 1981) as alternatives to peat. Additional research has been conducted on industrial and agricultural waste products. Some of these include coconut coir (Evans and Stamps, 1996), composted rice hulls (Laiche and Nash, 1990), processed poultry feath¬ers (Evans, 2004), kenaf (Wang, 1994), and composted animal manures (Tyler et al., 1993).Many of these alternative substrates were discarded due to their chemical or physical properties not meeting the needed properties for the substrate mix as used by the industry. Additionally, expense eliminated or great¬ly slowed others, such as ground bovine bone as a replacement for perlite (Evans, 2004).Rice hulls are a by-product of the rice milling indus¬try in Arkansas and across the United States. It has been estimated that 31 million metric tons of fresh rice hulls are produced annually in the United States (Kamath and Proctor, 1998).Fresh rice hulls have not been used in potting sub¬strates in the past because it was believed they caused nitrogen depletion. However, it was recently found that nitrogen depletion did not occur to any significant extent (Evans and Gachukia, 2004) when fresh rice hulls are used as a component in substrates. Furthermore, rice seeds have been a common contaminant of rice hulls and, therefore, created a weed problem (Evans and Gachukia, 2004). However, parboiled rice hulls were found to be free of viable weed seeds (Evans and Gachukia, 2004). All previous research conducted with rice hulls has replaced perlite and used whole parboiled fresh rice hulls to provide for drainage and air-filled pore space. Substrate particle size directly affects pore size. Large particles create large pores that drain and become air- filled after irrigation. Small particles create small pores that retain water for use by the plant. By grinding rice hulls, the particle size is reduced. The smaller-sized rice hull particles should create small pores that hold water. Thus, ground rice hulls (GRH) might be used as an alternative to peat. Further, grinding destroys any viable rice seed eliminating the weed problem and allowing for the use of non-parboiled hulls.Surfactants are used in the horticultural industry to increase the water-holding capacity of substrates. These surfactants are used on many alternative substrates to increase water-holding capacity. Their use might allow for the use of other alternative substrates which might not otherwise be useful due to low water-holding capac¬ity. Ground rice hulls may not provide sufficient water¬holding capacity and therefore may require that a surfac¬tant be added to increase water-holding capacity.The objective of this research was to determine if ground rice hull products could be used as an alternative to peat in the production of seedlings.MATERIALS AND METHODSRice hulls were acquired from Riceland Foods (Stuttgart, Ark.) and ground in a Wiley Hammer Mill (Arthur H. Thomas Co., Philadelphia, Penn.). This process created a product in which 98% of the particles were less than or equal to 2.0 mm in size (Fig. 1). The ground rice hulls (GRH) either remained untreated or were treated with the surfactant Soax (Scotts, Marysville, Ohio) at the recommended label rate.Substrates were formulated by blending the GRH, peat, and perlite (4 to 6 mm). All substrates contained 10% per¬lite and 30, 60, or 90% GRH with the remainder being peat. Calcitic limestone was added to the peat to adjust its pH to approximately 5.5. Two control treatments were evaluated. One control consisted of 90% peat and 10% perlite with no surfactant. An additional control substrate of 100% vermiculite was also included.Substrates were placed into five-cell-by-five-cell mini-plug trays, made from round #273 (5 ml volume per plug cell) plug trays. One tomato seed (‘Early Girl’) was plant¬ed per cell. Plug trays were then transferred to a bi-wall polycarbonate-glazed greenhouse. The low-temperature set point was 18°C. Light levels averaged 250 |^mol . sec-1 . m-2 at 12 h. The trays of substrates were misted once or twice daily to ensure a constantly moist substrate required for germination. All trays were misted at the same time, thus applying the same amount of water to all substrates. The mini-plug trays were fertilized with a 25 mg . L-1 nitro¬gen solution using N-P-K 15-5-15 Excel (Scotts, Marysville, Ohio) with every misting from the start of the third week until the experiment was terminated at the end of the fifth week. There were eight treatments with three replications, with a tray being a replication. The replica¬tions were placed on the greenhouse bench in a random pattern.An analysis of variance was run to establish if there were significant differences in seedling germination and growth among the different substrates. A least significant difference mean separation test (a = 0.05) was used to ascertain which means were significantly different.
RESULTS AND DISCUSSION
Seedlings grown in vermiculite had higher per-tray fresh shoot weights than seedlings grown in all other sub¬strates (Table 1). Seedlings grown in the 90% GRH with¬out surfactant and 60% GRH with surfactant had similar fresh shoot weights as the 90% peat substrate. All other GRH-containing substrates had lower fresh shoot weights than the 90% peat control.
Vermiculite, 90% GRH without surfactant, and 90% peat all had similar per-tray fresh root weights (Table 1). The 30% GRH with surfactant, 60% GRH without surfac¬tant, and 90% GRH with surfactant had lower fresh root weights per tray than the 90% peat control.
Seedlings grown in 90% GRH without surfactant, 60% GRH with surfactant, 90% peat, and 100% vermicu¬lite all had similar dry shoot weights. The 90% GRH with surfactant, 60% GRH without surfactant, and 30% GRH with surfactant had similar dry shoot weights per tray but were significantly lower than the controls. All seedlings had similar per-tray dry root weights regardless of the substrate. The germination percentage was similar for all substrates except the 30% GRH with surfactant, which was significantly lower than the 90% peat or 100% ver¬miculite controls.
Fresh shoot weights per plant for vermiculite and 90% GRH without surfactant were similar (Table 2). The fresh shoot weights per plant were similar for seedlings grown in 90% peat, 90% GRH without surfactant, and 60% GRH with surfactant. However, the 90% peat and 60% GRH with surfactant were significantly lower than ver¬miculite. Seedlings grown in 30% GRH-without-surfac- tant, 60% GRH-without-surfactant, 30% GRH-with-sur- factant, and 90% GRH-with-surfactant substrates had lower per-plant fresh shoot weights than those grown in the 90% peat and vermiculite controls (Table 2).
The average fresh root-weights per plant for seedlings grown in the two controls of 90% peat or 100% vermicu- lite were similar to the 90% GRH without surfactant. All other seedlings grown in GRH-containing substrates had similar average fresh root-weights per plant and were sig¬nificantly