Marcos Vinicios Garbiate

Decomposição e liberação de nutrientes de resíduos culturais de crambe e nabo forrageiro

This study aimed to evaluate the decomposition and nutrient release from crop residues of fodder radish and crambe in the implementation of no-tillage system. The experiment was conducted in a Distroferric Red Latossol with 762g kg-1 of clay. The experimental design was randomized blocks with four replications. The treatments were applied in split plots, considering the species of cover crops (radish and crambe) as the main plots and harvest dates of decomposition bags (0, 15, 30, 45, 60, 75 days after management) as subplots. The cover crops were treated 60 days after management, in full bloom. Radish presented a dry mass production of 5586kg ha-1 and crambe of 2688kg ha-1. The kinetics of residue decomposition had a behavior similar to the dynamics of nutrient release, with an initial rapid phase followed by a slower one. The K, P and Mg are released more quickly for subsequent crops. The increased speed of nutrients release by crops occurred around 15 days after the biomass management.

Erosão em entre sulcos em área cultivada com cana crua e queimada sob colheita manual e mecanizada

Although a number of studies related to environmental issues address air pollution, the increased use of biotechnology and mechanical harvesting of sugar cane, less attention has been paid to the negative environmental impacts caused by laminar erosion. This study aimed to determine the levels of organic matter (OM) and nutrients (P, K, Ca and Mg) in sediment and runoff water from interrill erosion from different sugarcane harvest systems (green and burnt cane), on a loamy Dystrophic Red Latosol (Oxisol). The treatments consisted of burnt cane harvested by hand, mechanical harvesting of green cane and mechanical harvesting of burnt cane. A portable rainfall simulator was calibrated to apply rainfall of 60 mm h-1, for 50 min. The sediment concentration in runoff resulting from interrill erosion, as well as OM, P, K, Ca and Mg were higher in the system with mechanical harvesting of burnt cane, while losses were lowest from the system with mechanized harvesting of green cane. The soil physical quality is negatively influenced by the management system with mechanical harvesting of burnt cane, due to the pressure exerted by the harvest machine traffic. However, crop residues distributed across the soil surface at mechanical harvesting of green cane reduce losses of soil, nutrients and OM in the sediment, and increase the soil resistance against physical degradation caused by machinery traffic for mechanical harvesting of sugarcane.

Infiltração de água no solo em áreas cultivadas com cana-de-açúcar sob diferentes sistemas de colheita e modelos de ajustes de equações de infiltração

As tecnicas de colheita da cultura de cana nem sempre seguem preceitos conservacionistas, fato que pode influenciar atributos fisicos do solo com consequente alteracao da velocidade de infiltracao de agua no solo. O trabalho realizado teve como objetivo avaliar o efeito de diferentes sistemas de colheita (manual e mecanizada) da cana-de-acucar (crua e queimada), sobre as caracteristicas de infiltracao e verificar a adequacao de modelos matematicos para a estimativa da taxa de infiltracao de agua no solo. Foi utilizado um simulador de chuva portatil calibrado para aplicar uma precipitacao de 60 mm h-1. Os testes de infiltracao de agua no solo foram realizados em tres sistemas de colheita: colheita manual de cana queimada, colheita mecanizada de cana crua e colheita mecanizada de cana queimada. A qualidade do ajuste dos modelos foi avaliada por meio de regressoes nao lineares entre os valores estimados e os valores medios observados em cada tratamento estudado. Nos tratamentos onde foi empregada a colheita mecânica, observou-se uma reducao da taxa de infiltracao final em relacao a area sob colheita manual de cana queimada. A equacao de Horton foi a mais adequada para a estimativa da taxa de infiltracao de agua no solo estudado.

Matéria seca e acúmulo de macronutrientes na parte aérea das plantas de Crambe

Crambe (Crambe abyssinica) has shown potential for biodiesel production because of high oil content in grains. Furthermore it is a viable option in crop rotation systems. Nevertheless, there are few studies about nutrient uptake by crambe plants. The aim of this work was to determine dry matter and nutrient accumulation in crambe shoots in different growth stages. The experiment was carried under a randomized complete block design with five replications. Shoot sampling was done at 14, 28, 42, 56, 70 and 84 days after seedling emergence. Each plant sample was separated in leaves (blade and petiole), stems+benches and fruit (capsules). The samples were dried, weighted and levels of N, P, K, Ca, Mg and S were determined. Plant leaves greatly contribute to dry matter production in initial stages of development. Leaf senescence is accentuated and the contribution from stems and branches is higher from flowering. The following nutrient demand by plant shoot was observed: N>Ca>P>S>K>Mg. Nutrients are exported by harvested grains as follows: N>P>S>Mg>Ca>K. Dry matter produced by shoots and fruit is low; however, sowing fertilization is essential to obtain satisfactory results due to a short plant cycle and fast transition period between flowering and fruit maturation.

Eficiência agronômica de superfosfato triplo e fosfato natural de Arad em cultivos sucessivos de soja e milho

Conduziu-se este estudo, com o objetivo de avaliar os efeitos de doses de adubos fosfatados sobre a cultura da soja e do milho, em cultivos sucessivos. O experimento foi realizado em casa de vegetacao da UFGD, em vasos contendo amostras de 5,5 dm3 de um Latossolo Vermelho Distroferrico argiloso, sendo utilizado como fontes de fosforo (P) o superfosfato triplo (SFT) e o fosfato natural de Arad (FNA). O FNA foi utilizado sob duas formas. Em uma, considerou-se o P total (Arad T) e, em outra, apenas a fracao de P soluvel em acido citrico a 2% (Arad SA), resultando em tres fatores de estudo, cada um em seis niveis de P (0, 56, 112, 224, 336 e 560), expressos em mg dm-3. A soja foi semeada em dezembro de 2006 e ao final do ciclo, efetuou-se a colheita, avaliando-se a produtividade de graos, teores de P na folha e no solo. Apos o cultivo da soja, semeou-se o milho, cuja colheita das plantas ocorreu aos 76 dias apos a semeadura, sendo avaliados a producao de massa seca da parte aerea e teores de P na folha. O indice de eficiencia agronomica foi calculado para ambas as culturas. Conclui-se que, para o primeiro cultivo (soja), o SFT apresentou um melhor desempenho no que se refere a produtividade de graos, quando comparado ao FNA. No cultivo do milho em sucessao a soja, o FNA tendeu a equiparar-se ao SFT nos atributos avaliados.