Top Dry Mass Research Articles

Produtividade de fitomassa e relação C/N de monocultivos e consórcios de guandu-anão, milheto e sorgo em três épocas de corte

Objetivou-se com este trabalho avaliar o rendimento de fitomassa, o acúmulo de N e a relação C/N da matéria vegetal produzida em monocultivos e consórcios de guandu-anão (Cajanus cajan), sorgo (Sorghum bicolor) e milheto (Pennisetum glaucum), em três épocas de corte. O experimento foi realizado em Presidente Prudente (SP), entre março e julho de 2006. Utilizou-se o delineamento experimental em blocos aos acaso, no esquema fatorial, com os seguintes tratamentos: monocultivos de sorgo, guandu-anão e milheto, e consórcios de sorgo + guandu-anão, milheto + guandu-anão e milheto + sorgo, com épocas de corte aos 30, 60 e 90 dias após a semeadura. O milheto é mais expressivo quanto à rapidez de crescimento nos primeiros 60 dias após a semeadura, de tal forma que domina o guandu-anão e o sorgo em consórcio, e produz mais fitomassa nas culturas consorciadas do que em monocultivo. O corte ou manejo das culturas consorciadas de milheto + guandu-anão e sorgo + guandu-anão no ambiente de safrinha, deve ser realizado aos 60 e 90 dias após a semeadura, respectivamente. Na consorciação de sorgo + guandu-anão há maior sincronismo de crescimento entre ambas as espécies, o que favorece o equilíbrio na composição da fitomassa da cultura de cobertura. Nos consórcios de guandu-anão com as gramíneas ocorrem maiores acúmulos de N nas palhadas do que no monocultivo de guandu-anão, e menores valores de relação C/N em relação aos monocultivos de milheto e sorgo.

Effects of partial root-zone drying on yield, tuber size and water use efficiency in potato under field conditions

Water resources are limited for irrigation worldwide; therefore, there is a need for water-saving irrigation practices to be explored. Partial root-zone drying (PRD) is a new water-saving irrigation strategy being tested in many crop species. Experiments were conducted in potato ( Solanum tuberosum L. cv. Folva) under open field conditions in 2004 and under a mobile rainout shelter in 2005. Two subsurface irrigation treatments were studied: full irrigation (FI) receiving 100% of evaporative demands, 50.1 and 201 mm of irrigation water in the 2 years, to keep it close to field capacity; and PRD, which received 21.7 and 140 mm of irrigation in 2004 and 2005 respectively. Due to rain in 2004, the PRD treatment was imposed over a short period only during the late tuber filling and maturing stages. In 2005, the PRD treatment was imposed during the whole period of tuber filling and tuber maturation. The PRD treatment was shifted from one side to the other side of potato plants every 5–10 days. Especially in 2005 it was apparent that stomatal conductance was generally lower in the PRD than in the FI plants, whereas leaf water potential tended to be lower in only a few instances. During the treatment period, plants were harvested five times, and no significant difference was found between the treatments in leaf area index, top dry mass and tuber yield. At final harvest, tubers were graded based on size into four classes C 1–C 4, of which the yield of the important marketable class (C 2) was significantly higher (20%) in the PRD than in the FI treatment. Compared with FI, the PRD treatment saved 30% of irrigation water while maintaining tuber yield, leading to a 61% increase of irrigation water use efficiency. The limited data of 2004 support these results. In summary, PRD is a promising water-saving irrigation strategy for potato production in areas with limited water resources.

Early rooting of dormant hardwood cuttings ofPopulus: analysis of quantitative genetics and genotype × environment interactions

Rooting of hardwood cuttings is under strong genetic control, although genotype × environment interactions affect selection of promising genotypes. Our objectives were (1) to assess the variation in rooting ability among 21 Populus clones and (2) to examine genotype × environment interactions to refine clonal recommendations. The clones belonged to five genomic groups ((Populus trichocarpa Torr. & Gray × Populus deltoides Bartr. ex Marsh.) × P. deltoides 'BC'; P. deltoides 'D'; P. deltoides × Populus maximowiczii A. Henry 'DM'; P. deltoides × Populus nigra L. 'DN'; and P. nigra × P. maximowiczii 'NM'). Cuttings, 20 cm long, were planted in Iowa and Minnesota in randomized complete blocks at 1.2 m × 2.4 m spacing, across three planting dates during 2001 and 2002. We measured nine belowground and aboveground traits from harvested cuttings after 14 days of growth. Percent rooting ranged from 22% to 86%. Broad-sense heritability for root and top dry mass ranged from 0.09 to 0.11 and 0.31 to 0.38, respectively. There were genotype × environment interactions for most traits, with belowground growing degree-days accounting for >54% of environmental variation. Clonal rooting was stable, except at Westport, Minnesota, during 2002, when root growth was relatively poor.

Response of sweet potato cultivars to acid soil infertility factors. I. Effects of solution pH on early growth

Sweet potato [Ipomoea batatas (L.) Lam.] is cultivated on soils varying widely in chemical properties, but relatively little is known about the effects of pH on the growth of this crop. In commercial and subsistence agriculture, sweet potato is propagated mostly from stem cuttings. This paper reports effects of a range of pH treatments (3.5–8.0) in flowing solution culture on early growth from cuttings of 15 sweet potato cultivars. Root growth was either greatly reduced or inhibited at pH 3.5. Increasing the pH to 4.0 markedly increased root development. Further increases in solution pH from 4.0 to 8.0 did not appear to affect root growth in most cultivars. Top growth in most cultivars showed a tendency to increase when pH was increased from 3.5 to 5.5 before declining with further increases in solution pH. The sweet potato cultivars studied differed widely in their tolerance to low pH, producing 16–48% of maximum top dry mass at pH 3.5. Tissue analysis from selected cultivars showed that K and Ca appeared to be limiting at pH 3.5, while P may have been deficient at pH 8.0. Results of this study indicate that low pH per se does not appear to be a major factor responsible for poor sweet potato yields in acid soils.

Biostimulants and Soil Amendments Affect Two-year Posttransplant Growth of Red Maple and Washington Hawthorn

Humate-based products have been aggressively marketed as biostimulants that increase plant growth. Little data are available on their effect on tree establishment or their interaction with fertilizer and irrigation regimes. This experiment tested several types of biostimulants on posttransplant growth of Acer rubrum L. (red maple) and Crataegus phaenopyrum (Blume) Hara (Washington hawthorn) trees, both with and without irrigation and fertilization. Soil treatments were applied at planting as: 1) control (native backfill only); 2) compost (native backfill + yard-waste compost); 3) peat (native backfill + Canadian sphagnum peat); 4) granular humate, 100 g/tree; 5) granular humate, 200 g/tree; and 6) liquid humate +, a proprietary liquid mixture of humate, kelp extract, thiamine, and intermediate “metabolites.” Irrigation regime × soil treatment interaction was significant for red maple, but soil treatments did not increase height, stem diameter, top dry mass, or root length. For Washington hawthorn, soil treatments did not increase height, stem diameter, or root length, but top dry mass in all treatments as a group and in humate-treated trees in particular was greater than that of controls. Roots of peat-treated trees of both species were longer than those in other treatments. Granular humate applied at 200 g/tree increased total root length more than did 100 g/tree in Washington hawthorn but not in red maple. Fertilizing at planting with N at 14.5 g·m-2 had no effect on any parameter measured for either species.

Biostimulants and Soil Amendments Affect Two-year Posttransplant Growth of Red Maple and Washington Hawthorn

Humate-based products have been aggressively marketed as biostimulants that increase plant growth. Little data are available on their effect on tree establishment or their interaction with fertilizer and irrigation regimes. This experiment tested several types of biostimulants on posttransplant growth of Acer rubrum L. (red maple) and Crataegus phaenopyrum (Blume) Hara (Washington hawthorn) trees, both with and without irrigation and fertilization. Soil treatments were applied at planting as: 1) control (native backfill only); 2) compost (native backfill + yard-waste compost); 3) peat (native backfill + Canadian sphagnum peat); 4) granular humate, 100 g/tree; 5) granular humate, 200 g/tree; and 6) liquid humate +, a proprietary liquid mixture of humate, kelp extract, thiamine, and intermediate “metabolites.” Irrigation regime × soil treatment interaction was significant for red maple, but soil treatments did not increase height, stem diameter, top dry mass, or root length. For Washington hawthorn, soil treatments did not increase height, stem diameter, or root length, but top dry mass in all treatments as a group and in humate-treated trees in particular was greater than that of controls. Roots of peat-treated trees of both species were longer than those in other treatments. Granular humate applied at 200 g/tree increased total root length more than did 100 g/tree in Washington hawthorn but not in red maple. Fertilizing at planting with N at 14.5 g·m-2 had no effect on any parameter measured for either species.

Response of Shade Trees Grown in In-ground Containers to Three Container Substrates

Abstract Two-year-old branched seedling whips of green ash, Fraxinus pennsylvanica Marsh. and European birch, Betula pendula Roth, were grown for two seasons (1991 and 1992) in 38-liter (# 10) rigid, plastic, in-ground containers in three different substrate treatments: 10%, 50% and 100% soil, containing 10:30:60, 50:30:20, or 100:0:0 of field soil:sphagnum peat:ground pine bark, respectively. Trees were also planted directly into the soil (field-grown) to serve as a baseline control treatment. Top dry mass, trunk diameter and root dry mass in 1991 and 1992 and two size categories of root dry mass (<3 and 3<6 mm) in 1991 were consistently greatest for container-grown trees in the 10% soil treatment and least in the 100% soil treatments. Corresponding results for the 50% soil treatment were intermediate between the other treatments or similar to the 10% soil treatment. In 1991, the top dry mass and trunk diameter of both species grown in containers with 10% soil and in 1992, the top dry mass of ash, in the same treatment, were greater than those of field-grown trees.

Short and Long-Term Effects of Treeshelters on the Root and Stem Growth of Ornamental Trees

Short-term (aerated solution culture and container nursery) and long-term (landscape) experiments were conducted to study the effect of treeshelters on the root and shoot growth of several ornamental trees {Sequoia sempervirens (D. Don) Endl., Quercus lobata Nee, Quercus agrifolia Nee, Lagerstroemia indica L. 'Watermelon Red', Ginkgo biloba L, Platanus racemosa Nutt., Fraxinus latifolia Benth. and Populus euamericana cv. Giacometti). In general, plants grown in treeshelters were taller and some had reduced caliper growth. Treeshelters reduced top dry mass of F. latifolia, P. racemosa, Q. agrifolia, Q. lobata and P. euamericana and also reduced root dry mass, root:shoot ratio, total root length and total root area for all species/cultivars except Q. agrifolia. The results are explained on the basis of the microenvironment in/ around treeshelters, photosynthetic partitioning and immobilization of plants growing in shelters. Management challenges and potential usefulness of treeshelters in landscape transplanting are also discussed.

Impact of Pinching Method and Number of Cuttings on Growth of Eight Florist Azalea Cultivars

During Fall 1995–Winter 1996, rooted cuttings of eight Rhododendron Simsii cultivars—Dorothy Gish, Jacinth, Paloma, White Gish, Friedhelm Scherrer, Gloria, Helmut Vogel, and Inga were transplanted July 1995 into 10.5-cm pots. A treatment consisted of one, two or three cuttings per pot. Cuttings were pinched either mechanically using a hedge clipper (control) or chemically with Off-Shoot-O at rates of 63.5 or 111.1 mL·L–1 of water or with Atrimmec at 20 mL·L–1 of water. Pinching treatments were repeated three times during the experimental period. New secondary shoots developed more rapidly after a mechanical pinch than after a chemical pinch. Moreover, greater foliage damage was observed on plants pinched with Off-Shoot-O. Growth measurements (height and diameter of plants, top dry mass, number of days to reach anthesis and visual quality) will be presented.

Influence of Compost Aging and Fertilizer Regimes on the Growth of Bedding Plants, Transplants and Poinsettia

Abstract Rooted cuttings of poinsettia (Euphorbia pulcherrima Willd. ex Clotzsch ‘Amy’) and seedlings of bibb lettuce (Lactusa sativa L.), baldhead cabbage (Brassica oleracea L. var. Capitata), sweet william (Dianthus barbatus L.) and pansy (Viola & Wittrockiana Gams.) were grown in Sunshine Mix and 7 experimental media containing 30-day-old (“New”) or 90-day-old (“Aged”) cocompost (polymer dewatered sewage sludge composted with processed garbage), perlite or vermiculite, and peatmoss. Plants were fertilized biweekly with water soluble fertilizer of 25N-2.2P-16.6K (25-5-20) at 250 ppm of N applied at 0, 1 or 2 wks after transplanting. The growth of all species did not vary with compost age. Dianthus and pansy plants grown in 50% “New” compost and dianthus grown in 25% “New” compost produced significantly lower top dry mass than those grown in Sunshine Mix. All other treatments for cabbage, lettuce, dianthus and pansy showed no significant difference in top growth from those grown in Sunshine Mix. Poinsettia plants grown in Sunshine Mix produced greater total growth than all other treatments except those grown in equal portions of “New” compost, peat and perlite. Lettuce and cabbage leaf tissue contained cadmium levels less than 0.5 ppm regardless of compost level.