Orchid growth and nutrition in response to mineral and organic fertilizers

Orchid fertilization is fundamental for a satisfactory plant growth and development for commercial orchid production as well as in collections. Mineral and/or organic sources can be used for fertilization. The objective of this study was to evaluate the effect of the use of organic and/or mineral fertilizers on the nutrition and growth of orchid (Laelia purpurata 'werkhanserii' x L. lobata 'Jeni') seedlings in greenhouse. The following fertilizers were tested: an NPK fertilizer + micronutrients; a Ca source in the form of calcium nitrate; two organic fertilizers, one prepared with a mixture of bone meal, castor meal and ash, and a similar commercial fertilizer. The organic fertilizers were distributed on the surface of the pots every two months and the minerals were applied weekly to the substrate in 25 mL aliquots of a solution containing 1 g L-1 of the respective fertilizer. The plant response to the application of mineral together with organic fertilizer was better, with higher dry matter production than by the isolated application of each fertilizer (organic or mineral). The treatments with calcium nitrate + NPK fertilizer did not differ significantly from the use of NPK fertilizer, probably due to the S deficiency detected in a mineral analysis of the tissues. Commercial organic fertilizer had a very elevated B level, leading to toxicity symptoms, reduced growth and necrotized tips of the older leaves in all fertilized treatments.

NPK fertilization on initial growth of physic nut seedlings in Quartzarenic Neossol

Balanced fertilization is important for plant growth. There is little information on physic nut (Jatropha curcas L.) and tests with the fertilization of the species are very recent. This study evaluated the initial growth of physic nut seedlings in response to NPK rates to Quartzarenic Neossol in a greenhouse and estimated P and K critical soil levels and N, P and K in shoot dry matter after 120 days of evaluation. The treatments were arranged in a randomized, fractional factorial design (4 x 4 x 4)½, totalizing 32 treatments with three replicates, 96 experimental plots and N rates (0, 75, 150 and 300 mg dm-3) as urea; P rates (0, 45, 90 and 180 mg dm-3) as triple superphosphate and K rates (0, 50, 100 and 200 mg dm-3) as potassium chloride. After 120 days, the plants were harvested and some variables evaluated: plant height, stem diameter, shoot and root dry weight, macro and micronutrient levels in plant shoots, and soil chemical properties. The physic nut seedlings responded to NPK fertilizer in the initial growth phase; the response to N was negative. The recommended P and K rates were 25 and 67 mg dm-3, respectively. The critical levels, corresponding to the recommended P rate were 13 and 74 mg dm-3 for K in soil (Mehlich-1). The N, P and K levels in the shoot dry matter of physic nut were 37.4, 2.1 and 35.7 g kg-1, respectively.

Root growth of tomato seedlings intensified by humic substances from peat bogs

Peats are an important reserve of humified carbon in terrestrial ecosystems. The interest in the use of humic substances as plant growth promoters is continuously increasing. The objective of this study was to evaluate the bioactivity of alkaline soluble humic substances (HS), humic (HA) and fulvic acids (FA) isolated from peats with different decomposition stages of organic matter (sapric, fibric and hemic) in the Serra do Espinhaço Meridional, state of Minas Gerais. Dose-response curves were established for the number of lateral roots growing from the main plant axis of tomato seedlings. The bioactivity of HA was greatest (highest response in lateral roots at lowest concentration) while FA did not intensify root growth. Both HS and HA stimulated root hair formation. At low concentrations, HS and HA induced root hair formation near the root cap, a typical hormonal imbalance effect in plants. Transgenic tomato with reporter gene DR5::GUS allowed the observation that the auxin-related signalling pathway was involved in root growth promotion by HA.

Growth, nodulation and nitrogen fixation of cowpea in soils amended with composted tannery sludge

Tannery wastes generation is increasing every year and a suitable method for tannery sludge management is necessary in order to decrease this environmental problem. The composting is recognized as a suitable method for sludge recycling.. The effect of tannery sludge compost (TSC) rates on growth, nodulation and N fixation of cowpea was investigated. Sandy and clayey soils were amended with TSC at rates of 0, 7.5, 15, 30, and 60 t ha-1. The shoot dry weight of cowpea plants 45 days after emergence (DAE) was greater in the TSC-amended than in the unamended soil. In the sandy soil, nodule dry weight increased with TSC application 45 DAE. In the clayey soil, 45 DAE, nodule dry weight decreased with TSC amendment levels greater than 7.5 t ha-1 compared to the unamended control. The application of TSC increased N accumulation in the cowpea plants. The results suggest that cowpea responds differently to TSC depending on the amendment rate and initial soil type.

Soil physical properties and sugarcane root growth in a red oxiso

Sugarcane, which involves the use of agricultural machinery in all crop stages, from soil preparation to harvest, is currently one of the most relevant crops for agribusiness in Brazil. The purpose of this study was to investigate soil physical properties and root growth in a eutroferric red Oxisol (Latossolo Vermelho eutroférrico) after different periods under sugarcane. The study was carried out in a cane plantation in Rolândia, Paraná State, where treatments consisted of a number of cuts (1, 3, 8, 10 and 16), harvested as green and burned sugarcane, at which soil bulk density, macro and microporosity, penetration resistance, as well as root length, density and area were determined. Results showed that sugarcane management practices lead to alterations in soil penetration resistance, bulk density and porosity, compared to native forest soil. These alterations in soil physical characteristics impede the full growth of the sugarcane root system beneath 10 cm, in all growing seasons analyzed.