Abstract Introduction: The Comarca Lagunera, located in the states of Coahuila and Durango, Mexico, is the region with the highest milk production in the country. In this region, dairy farms with agricultural areas for the production of forage crops are common, where excessive rates of manure are applied to the soil and nitrate contamination of groundwater has been reported; therefore, it is important to generate information on the manure available nitrogen (MAN) in a system of two crops per year. Method: A study was conducted with increasing doses of nitrogen (N), depending on the crop N requirement (CNR), using urea, corral manure (CM) and manure from the solid separator (SSM) as sources of N, in silage corn in spring and triticale in winter. The yield of the crops and the availability of N in both types of manure were evaluated. Results: Silage corn dry matter yield was similar in all treatments, from 13.9 to 15.5 t∙ha-1, except in the 133% CNR with SSM, which had the lowest yield. In triticale, the differences in yield were not significant. In corn, the dose of 428.6 kg∙ha-1 of total N with CM and 449.6 kg∙ha-1 of total N with SSM, had the same extraction of N (Nex) of 141.2 kg∙ha-1, equivalent to 185 kg∙ha-1 of N with urea fertilizer, which corresponds to 100% of the CNR. The above indicates an availability of N of 43.2% in CM and 41.1% in SSM. In the winter season, available N was 19.5% and 11.1% in CM and SSM, respectively. Conclusion: Available N from both types of manure provided enough of this nutrient for two forage crops. Values of available N were similar in both types of manure when estimated in the spring-summer season, but in autumn-winter the MAN was higher in the CM.

Resumen Introducción: La Comarca Lagunera, ubicada en los estados de Coahuila y Durango, México, es la región con la mayor producción de leche en el país. En esta región son comunes las explotaciones lecheras con áreas agrícolas para la producción de cultivos forrajeros, donde se aplican dosis excesivas de estiércol y se han reportado problemas de contaminación del agua por nitratos; por lo tanto, es importante generar información sobre el nitrógeno disponible del estiércol (NDE) en un sistema de dos cosechas por año. Método: Se realizó un estudio con dosis crecientes de nitrógeno (N), en función del requerimiento de N del cultivo (RNC), utilizando urea, estiércol de corral (EC) y estiércol del separador de sólidos (ESS) como fuentes de N, en cultivos de maíz forrajero en primavera-verano y triticale en otoño-invierno. Se evaluó el rendimiento de los cultivos y el NDE en ambos tipos de estiércol. Resultados: El rendimiento de materia seca de maíz fue similar en todos los tratamientos, de 13.9 a 15.5 t∙ha-1, excepto en la dosis de 133% RNC con ESS, que tuvo el rendimiento más bajo. En triticale, las diferencias en rendimiento fueron no significativas. En maíz, la dosis de 428.6 kg∙ha-1 de N total con EC y de 449.6 kg∙ha-1 de N total con ESS, tuvieron la misma extracción de N (Nex) de 141.2 kg∙ha-1, equivalente a la dosis de 185 kg∙ha-1 de N con urea, que corresponde al 100% del RNC. Lo anterior indica una disponibilidad de N de 43.2% en EC y 41.1% en ESS. En el ciclo de invierno, el N disponible fue de 19.5% y 11.1% en EC y ESS, respectivamente. Conclusión: El N disponible de ambos tipos de estiércol, EC y ESS, abasteció de manera suficiente a dos cultivos forrajeros. Los valores de NDE fueron similares en ambos tipos de estiércol cuando se estimó en ciclo de primavera-verano, pero en otoño-invierno el NDE fue mayor en el estiércol de corral.

RESUMO O potássio (K) influencia as variáveis que determinam a qualidade dos frutos e a concentração de fitonutriente para a saúde humana e, portanto, as preferencias do consumidor. O objetivo desse estudo foi avaliar o efeito de diversas concentrações de K na solução nutritiva (5, 7, 9 e 11 mM de K) sobre o rendimento e qualidade de frutos de melão Cantaloupe em casa de vegetação. O experimento foi realizado em vasos, em delineamento experimental completamente casualizado, com 15 repetições. Foram analisadas a variância, correlação, regressão e comparação múltipla de médias (Tukey p<0,05). Obtiveram-se valores maiores de produtividade, peso médio de frutos, diâmetro equatorial, espessura da polpa, firmeza da polpa, teor de sólidos solúveis totais, teor de compostos fenólicos e capacidade antioxidante dos frutos nas concentrações de 9 e 11 mM de K. Todas variáveis, com exceção de diâmetro polar dos frutos, tiveram seus valores aumentados, com concentrações crescentes de K, evidenciando tendência linear positiva e significativa, indicando que a dose ótima de K em melão é superior a 11 mM. Assim, sugere-se para pesquisas futuras, avaliar concentrações acima de 11 mM..

ABSTRACT Potassium (K) influences the variables that determine quality of fruit and the concentration of phytonutrients to human health and therefore consumer preferences. The objective of this study was to evaluate the effect of different concentrations of K in the nutrient solution (5, 7, 9 and 11 mM of K) on yield and quality of Cantaloupe fruits under greenhouse conditions. The experiment was conducted in pots using a completely randomized design with 15 replications. Analysis of variance, correlation, regression and multiple comparisons among means (Tukey p<0.05) were performed. Results showed higher values of yield, average fruit weight, equatorial diameter, pulp thickness, fruit firmness, soluble solids content, phenolic content and antioxidant capacity of fruits at the concentrations of 9 and 11 mM of K. All variables, except equatorial diameter, increased their values as K concentrations increased, showing a lineal, positive and significant trend, which evidences that the optimal dose of K in muskmelon is higher than 11 mM, being suggested for future research, to evaluate concentrations above this value.