The aim of this study was to evaluate the effect of sources and rates of organic waste and their interaction on the growth of Leucaena leucocephala (Lam.) de Wit, in the Southeast region of Piauí State. The treatments consisted of two sources (Copernicia prunifera (Mill.) H.E. palm residue and plant compound) and six organic waste rates. The study was conducted in the period of March-June 2011 and the following parameters were evaluated: stem diameter, height, number of leaves, shoot dry weight, root dry weight, total dry matter, root volume, shoot dry weight/root dry weight ratio, height/stem diameter ratio and the Dickson Quality Index. The Copernicia prunifera (Mill.) H.E. palm residue and plant compound showed a great potential to be used in the manufacture of substrates for the production of seedlings Leucaena leucocephala (Lam.) de Wit, since their initial development was influenced by the sources and proportions of these organic residues and by the interaction between these treatments. The substrate containing 50% of plant compound produced better quality of plants of Leucaena leucocephala (Lam.) de Wit in their initial development stage.

PALAVRAS-CHAVE RESUMO:O substrato é um dos fatores que exerce influência no desenvolvimento das mudas de espécies florestais. Inúmeros resíduos industriais e urbanos podem ser utilizados como fonte de nutrientes visando contribuir para a redução dos custos de produção de mudas e também podem ser uma saída para reduzir ou solucionar problemas ambientais. Objetivou-se avaliar a porcentagem e velocidade de emergência e o crescimento inicial de Sesbania virgata cultivada em substratos constituídos de diferentes resíduos orgânicos acrescidos de amostras de horizonte B de um Latossolo Amarelo. Os tratamentos foram constituídos das seguintes proporções: (v/v) de três resíduos (bagana de carnaúba, composto orgânico e palha de arroz): solo: 0:100; 20:80; 40:60; 60:40; 80:20, dispostos em delineamento inteiramente casualizado, em esquema fatorial (3 × 5), com 10 repetições. Foram avaliadas a porcentagem e a velocidade de emergência, variáveis relacionadas ao crescimento das plantas, suas relações, e o índice de qualidade de Dickson. As mudas de Sesbania virgata são responsivas à adição de resíduos orgânicos ao substrato constituído de amostras de subsolo, sendo que as melhores respostas foram obtidas quando se utilizou composto orgânico. A adição de palha de arroz ao substrato reduziu a porcentagem de emergência e o índice de velocidade de emergência das mudas de Sesbania virgata. As mudas cultivadas com os substratos constituídos de composto orgânico na proporção 88,48: 11,52 (composto orgânico:solo) apresentam maior índice de qualidade de Dickson, sendo, portanto, esta a proporção recomendada para a produção de mudas. : 0:100; 20:80; 40:60; 60:40; 80:20, disposed ABSTRACT: The substrate has great influence in forestall seedlings species development. Several industrial and urban wastes may be used as a source of nutrients to contribute to the reduction of seedling production costs and may help to reduce or solve environmental problems. This study aimed to evaluate the germination percentage, speed and initial growth of Sesbania virgata cultivated in substrates composed of organic residues plus samples horizon B of a yellow latosol. Treatments had the following proportions (v/v) of three residues (leave dust from carnauba, organic compound and rice husk): soil

The cover crop straw may cause changes in the microbial activity and population, with repercussions on environmental changes and on the C and N dynamics, providing important information for the planning of adequate land use in the Cerrado. The objective of this study was to evaluate the effect of straw of cover crops on the soil microbial attributes and quality of organic matter. Experimental units consisted of 100 g of sieved soil placed in small plastic cups mixed with straw from cover plants. Treatments were distributed in a CRD, in a factorial scheme of 7 x 7 + 1, with seven types of straw, evaluated at 7, 14, 21, 28, 42, 63 and 105 days after incubation, and control without straw, with three replicates. The qCO2 ranged from 0.1 (Crotalaria spectabilis at 14 days) to 5.1% (Cajanus cajan ‘IAPAR 43’ at 42 days). The organic carbon and nitrogen reservoir are differently affected by straw of legumes and grasses on the dates. The incorporation of Brachiaria brizantha and Mucuna aterrima had a positive impact on the microbial attributes until the 21st incubation (qCO2, Cmic and Nmic), with little loss of carbon dioxide and growth of the microbial population. All the evaluated species presented a potential to be used in crop rotation systems, enabling no-tillage systems in the Cerrado of Piauí. However, it is recommended to select species according to specific purposes. Thus, the use of cover crops is an important tool for increasing the biological quality of Brazilian northeastern cerrado soils.

Carbon and nitrogen from the soil microbial biomass play a significant role in the rotation of C and N, and promote nutrient cycling. Thus, the objective of this study was to evaluate changes in the soil microbial biomass with growing doses of cover plant straw species. The cover plants cultivated in the cerrado biome region were incorporated an Oxisol Ustox. The straw of each cover plant was incorporated at doses of 0; 10; 20 and 30 Mg ha-1. The soil basal respiration was determined by incubating, after 21 days. The microbial biomass carbon and nitrogen were determined by the method the microwave irradiation. The microbial biomass carbon and nitrogen contents in extracts were determined by the wet combustion method and Kjeldahl-N. The metabolic quotient was calculated as the ratio between soil basal respiration rate and microbial biomass C, and the microbial quotient as the ratio between soil microbial biomass C and total carbon of soil. The soil microbial population measured by the attributes of quality responds to the addition of the of grass and legume straws incorporated to the soil; The treatments that cause the greatest stress to the microbial population, at 21 days, mediated by the metabolic quotient, are guandu-anão at a dose of 10 Mg ha-1; Guandu-anão and Guandu fava-larga at 20 Mg ha-1 and Brachiária at a dose of 30 Mg ha-1; The best result regarding microbial attributes of soil quality evaluated was observed with the incorporation of all doses of the straw of Crotalaria-ocroleuca.