Marcos Brandão Braga

Frações ótimas da adubação com fósforo no pré‑plantio e na fertirrigação por gotejamento de tomateiro

The objective of this work was to establish the optimal fractions of the total amount of phosphorus to be applied in preplanting and in drip fertigation of determinate-growth tomato, as well as to determine the effect of the different forms of nutrient application on their soil spatial distribution. Treatments consisted of five schemes of fertilizer application: 100, 75, 50, 25, and 0% of P total dose divided between the pre-planting (triple superphosphate in band placement) and the fertigation (phosphoric acid). The experiment was carried out in a clayed Oxisol with two P availability classes - 7.5 and 32.9 mg dm-3 (Mehlich-1). The treatments showed no effect on tomato production variables in the soil with high P availability. However, in the soil with smaller availability of the nutrient, P fertigation showed a quadratic effect on fruit yield, net income, and net rate of return. The best results were obtained with half of the P total dose applied by fertigation. The fertigation allowed P movement in the soil up to 30 cm deep, and horizontal movement up to 15 cm.

Behavior vegetative and technological characteristics sugarcane cultivars under water stress in semi-arid conditions of Brazil

The water tends to become a natural resource increasingly scarce in temperature rise scenarios, especially in semi-arid regions. Therefore, the cultivation of sugarcane, seek to alternatives and techniques that optimize water efficiency. The objective of this study was to analyze the biometric features and the technological quality of seven cultivars of sugarcane: RB 96-1003; RB 94-3206; RB 72-454; RB 01-2018; VAT 90-212; RB 01-2046 and RB 92-579 submitted to four blades of fluid replacement: 40, 60, 80 and 100%, based on crop evapotranspiration. The evaluations were performed in sugarcane ratoon cycle of second sheet, irrigated by subsurface drip and consisted of analysis of height, stem diameter, number of internodes, number of tillers, °Brix, percentage of raw sugar, purity, fiber and reducing sugars. It was found that the maximum height can be achieved with lower water replacement blades; the stem diameter and the number of internodes are more characteristics related to the genetic component of the plant variety and the number of tillers is little influenced by the fluid replacement blades. It was found that sugarcane cultivars have technological characteristics of the broth that meet established standards, except that the fiber had a higher value than recommended. Biometric and technological characteristics of the juice can help in recommending more tolerant cultivars to water stress and thus more potential production scenarios temperature increases and water savings.

Produtividade de cultivares e populações de cenoura em sistema orgânico de cultivo

A cenoura e a quarta hortalica mais consumida no pais e uma das mais consumidas no mundo. Considerando a importância da selecao de materiais de cenoura, conforme a regiao e o sistema de cultivo, objetivou-se avaliar o comportamento de cultivares e populacoes de cenoura, sob manejo orgânico, nas condicoes do Submedio do Vale do Sao Francisco, no periodo de temperaturas amenas (junho a setembro de 2008). O experimento foi conduzido em delineamento de blocos ao acaso e tres repeticoes, com 13 cultivares (Brasilia, Alvorada, Karine, Brazlândia, Nantes, Suprema, Redonda de Nice, Nancy, Kuronan, Esplanada, Danvers, Tropical, Nova Kuroda) e tres populacoes (Alvorada POP, Brasilia POP e Esplanada POP). A altura de plantas oscilou de 48,0 a 64,1 cm, com destaque para a cultivar Brasilia (64,1 cm). A produtividade total de raizes variou de 65,2 a 98,9 t ha-1, sendo maior para os genotipos Brasilia POP (98,9 t ha-1), Brasilia (96,3 t ha-1) e Danvers (94,7 t ha-1). A produtividade comercial de raizes oscilou de 0,0 a 84,5 t ha-1, destacando-se os genotipos Brasilia POP (84,5 t ha-1), Brasilia (81,7 t ha-1) e Danvers (78,1 t ha-1). A cultivar Esplanada sobressaiu-se com maior massa fresca de raiz (123,2 g raiz-1), seguida pela cultivar Danvers (122,8 g raiz-1) e o genotipo Esplanada POP (119,1 g raiz-1), com a primeira e o ultimo nao apresentando maiores produtividades comerciais.

Evaluation of sources, doses and application schedules of nitrogen on drip-irrigated tomato

We aimed to establish strategies for nitrogen (N) fertilization on drip-irrigated determinate-growth-habit tomato, under Cerrado conditions of Central Brazil. Three field experiments were carried out in a randomized block design. In experiment I six N doses (0, 80, 160, 240, 320 and 400 kg ha-1 N) were tested, in experiment II six combinations of the N forms (nitric; ammonium; amide; 2/3 nitric + 1/3 ammonium; 2/3 nitric + 1/3 amide; and 1/3 nitric + 2/3 amide) were evaluated, and in experiment III the combination of three soil pre-plant fertilization fractions (0, 20 and 40%) was evaluated with two splitting schemes of the remaining N via fertigation (linear and adjusted N-uptake curve). SPAD chlorophyll index and N content were measured in the leaves of tomato plants on experiment I. The physical and economic yields of tomato crop were maximized for the doses of 287 kg N ha-1 and 270 kg N ha-1, respectively, with doses of 2.1 g and 2.0 g of N per kg of commercial fruit. The yield was maximized for 52 SPAD units. The combinations of forms and the application schedules of N had no significant effect on the yield components of the tomato crop.