RESUMO As sementes da maioria das culturas são frequentemente colhidas com um teor de água acima do recomendado; por exemplo, a cultura do amaranto pode ser colhida com teores de água até 40%. Portanto, a secagem da colheita é necessária para preservar a qualidade pós-colheita. Assim, objetivou-se estudar a cinética de secagem de sementes de Amaranthus cruentus ‘BRS Alegria’ secas por métodos naturais e artificiais. Os experimentos foram conduzidos em laboratório utilizando os métodos de secagem natural, sombra e pleno sol, e, secagem artificial nas temperaturas de 60, 80 e 100 °C. As médias das temperaturas da massa de sementes foram de 30, 40, 50, 60 e 70 °C respectivamente para os métodos de secagem natural, sombra e pleno sol, e, secagem artificial nas temperaturas de 60, 80 e 100 °C. A equação de Midilli modificada foi o melhor modelo para descrever a cinética de secagem de sementes de Amaranthus cruentus ‘BRS Alegria’. Para o método de secagem artificial nas temperaturas de 60, 80 e 100 °C, durações de 2,5, 3,5 e 7 horas foram necessárias, respectivamente, para reduzir o teor de água de 21,1% para 11,5%; e 4,25, 4,75 e 10 horas, para reduzir o teor de água de 21,1% para 8,5%. Para secagem natural a pleno sol, foi necessário um tempo de secagem de 15 horas; para condições de sombra, um tempo de secagem de 164 horas foi necessário até o teor de água ser reduzido para 13%, a umidade de equilíbrio.

ABSTRACT The seeds of most crops are often harvested with water concentrations above the recommended levels; for instance, amaranth crops can be harvested under water contents up to 40%. Therefore, drying of the harvest is essential to preserve its post-harvest quality. Thus, the objective of this study was to investigate the drying kinetics of Amaranthus cruentus ‘BRS Alegria’ seeds dried via natural and artificial methods. Drying experiments were conducted in laboratory under natural methods, in shaded and open sun conditions, and also under artificial drying at temperatures of 60, 80 and 100 °C. The average temperatures of the seed mass were 30, 40, 50, 60, and 70 °C for the natural drying methods, shaded and open sun, and under the artificial drying at temperatures of 60, 80, and 100 °C. The modified Midilli equation proved to be the best model for describing the drying kinetics of Amaranthus cruentus ‘BRS Alegria’ seeds. For the artificial drying method at temperatures of 60, 80, and 100 °C, durations of 2.5, 3.5, and 7 hours were respectively required to reduce the water content from 21.1% to 11.5%; and, 4.25, 4.75, and 10 hours to reduce concentration 21.1% to 8.5%. For natural drying under open sun, a drying time of 15 hours was required; for shaded conditions, a drying time of 164 hours was required until the water concentration reduced to 13% which was the equilibrium moisture.

O experimento foi conduzido na Fazenda Experimental da UFMT em Santo Antônio de Leverger, Estado do Mato Grosso, com o objetivo de avaliar as características agronômicas de híbridos de milho em cultivo de segunda safra para a produção de silagem. O delineamento experimental utilizado foi em blocos casualizados com 23 tratamentos (híbridos) e três repetições. As características agronômicas avaliadas foram diâmetro do colmo (cm); altura de plantas e da inserção de espiga (m); produtividade de matéria verde (t ha-1); porcentagens de espiga, colmo e folhas na massa verde; produtividade de espigas (t ha-1); teores de matéria seca do colmo + folha e da planta inteira. Os híbridos que apresentaram maiores valores para produção de matéria verde, altura de plantas e da inserção de espiga foram BF 9304, DKB 370, DKB 177, BF 9534, BF 9417, AG 5020, BE 9701, P 3021 e P 30F98. O híbrido BF 9304 também se destacou quanto à porcentagem de espiga (50,55%).

The experiment was conducted at the Experimental Farm of the Federal University of Mato Grosso in the municipality of Santo Antônio do Leverger, State of Mato Grosso, Brazil to evaluate the agronomic characteristics of corn hybrids in the cultivation of second crop for silage production. The experimental design was carried out with randomized blocks with 23 treatments (hybrids) and three replications. Corn hybrids from different seed companies and recommended for the midwestern region of Brazil, were used. The agronomic traits were: stem diameter (cm), plant height and ear insertion (m); yield of green matter (ton. ha-1), percentage of spike, stem and leaves in green mass; ear productivity (ton. ha-1), dry matter content of stem + leaf and whole plant. Hybrids BF 9304, DKB 370, 177 DKB, BF 9534, BF 9417, AG 5020, BE 9701, P 3021 and P 30F98 had the highest production of green matter, plant height and spike insertion. The hybrid BF 9304 was also prominent for spike percentage (50.55%).

This experiment was carried out in order to evaluate the effect of Sitophilus zeamais on physical, physiological and sanitary quality of stored corn. Samples of 500 g of the hybrid OC-705, in three replicates, were conditioned in glasses covered with a screened lid, and kept in chamber at 25±2ºC, 70±5% RH and 12 h of photophase, for 150 days. The infestation levels were 0, 5, 15 and 50 adults/replicate, for the storage periods of 30, 60, 90, 120 and 150 days. The moisture content, classification, weight loss, germination and internal infestation were evaluated monthly. Significant inverse correlations were verified between the number of insects and both the germination and the weight loss; also between the internal infestation and the germination and the standard type. The presence of S. zeamais showed a positive correlation with the weight loss, what means that the internal and external infestations contribute to the reduction of physiological and physical quality of corn seeds. The mean dry matter loss was 0,36%/day, corresponding to a consumption of 0,0001%/insect/month. As the result of those damages, the product suffered reduction of the commercial grade in 30 days, with significant loss in all quality factors.