Crude protein (CP) of forages can be separated into fractions of differentiated abilities to provide available amino acids in the lower gut of ruminants. This knowledge is critical to develop feeding systems and to predict animal responses. We have measured during two growing seasons (1996 to 1997 and 1997 to 1998) the CP fractions of common vetch fresh forage with the objective being to assess the influence of maturity on concentration of CP fractions (as a percentage of total CP) and fraction yields. Fraction B2, which represents true protein of intermediate ruminal degradation rate, was the largest single fraction in common vetch forage (about 40% of CP across seasons and maturity stages). Soluble fractions (A plus B1) were less than 50% of total CP while the unavailable fraction C ranged from 4 to 8% of total CP. As a result, the remaining fraction B3 (true protein of very low degradation rate) only represented 2 to 9% of total CP. Concentration and yield of fraction B3 increased (P < 0.05) from flowering to pod-filling. Results showed that undegraded dietary protein represented a small proportion of total CP in common vetch forage. Moving the harvesting stage from flowering to the pod filling phase allowed for greater yield of undegraded dietary protein.

Maize-soybean intercropping can increase forage quality with no detrimental effect on dry matter (DM) yield. The objective of this study was to compare corn-soybean intercrop in narrow strips with corn as monocrop in terms of DM yield and forage quality. This study was conducted in Matamoros, Coahuila (Mexico) in 2006 and 2007. Intercrops were established in rows spaced 0.50 m apart, evaluating alternate corn-soybean strips with one, two, three, and four rows per crop, and a treatment using an alternate twin-row planting pattern per crop, with a 1.0-m row-spacing. As control treatments, monocrops of corn in rows 0.76 m apart and soybean in rows 0.50 m apart were evaluated. A randomized complete block design with four replications was employed. Corn-soybean intercrop produced DM yields similar to those of monocropped corn due to higher corn yields in border rows adjacent to soybean. Crude protein (CP) yields per hectare in intercrop treatments were higher (27.5 to 42.8%) than those of monocropped corn, due to greater CP concentrations in intercrops (16 to 21 g kg -1 ). When soybean was harvested at the beginning maturity stage (R7), neutral detergent fiber concentration was reduced by 60 to 63 g kg -1 in corn-soybean intercropping compared to corn monocrop. Acid detergent fiber was not altered by intercropping. Results indicate that maize-soybean intercrop in narrow strips can provide forage quality advantages without affecting yield.Additional key words: chemical composition, dry matter and ear yields, dry matter partitioning, Glycine max, intraspecific competition, Zea mays. Resumen Rendimiento y calidad de forraje de maíz y soya asociados en franjas angostasLa asociación maíz-soya puede incrementar la calidad del forraje sin disminuir el rendimiento de materia seca (MS). El objetivo del estudio fue comparar la asociación maíz-soya en franjas angostas con maíz en unicultivo en términos de rendimiento de MS y calidad de forraje. El estudio se realizó en 2006 y 2007 en Matamoros, Coahuila, México. Las asociaciones se establecieron en surcos a 0,50 m, en franjas alternas de maíz y soya con uno, dos, tres y cuatro surcos por cultivo y un tratamiento en surcos alternos a 1 m con doble hilera del mismo cultivo. Los testigos fueron maíz y soya en unicultivo establecidos en surcos a 0,76 m y 0,50 m, respectivamente. Se utilizó un diseño experimental de bloques completos al azar con cuatro repeticiones. La asociación maíz-soya produjo rendimientos de MS similares a maíz en unicultivo como resultado de un mayor rendimiento del maíz en los surcos adyacentes a la soya. Debido al mayor contenido de proteína cruda (PC) (16 a 21 g kg -1 ), las asociaciones produjeron rendimientos de PC ha -1 superiores a maíz en unicultivo entre 27,5 y 42,8%. Cuando la soya se cosechó en la fase de inicio de maduración (R7), el contenido de fibra detergente neutro en las asociaciones se redujo entre 60 y 63 g kg -1 en relación a maíz en uni-

The aim was to evaluate yield of forage, grain and biomass and fibre content of eight hybrids of maize (Rio-Grande, Arrayan, Genex 778, Narro 2010, Advance 2203, DAS 2358, P4082W and HT9150W) during two sowing seasons (spring/summer) for two consecutive years at La Laguna in Torreon, Mexico. Once the grain progression of the kernel milk line was ⅓, green forage yield (GFY), dry matter (DM), neutral detergent fiber (NDF) and acid detergent fiber (ADF) were determined. When the corncobs were fully mature, grain yield (GY) and biomass production (TBP) were determined. Weather conditions were recorded during the experiment. The results indicated that maximum temperature was higher and rainfall lower in the summer sowing and second year. Spring sowing had significantly higher yields of GFY, DM, GY and TBP compared to summer sowing. The first year of study showed significantly higher yields regarding GFY, GY and TBP, but FDN, FDA, DM content compared to the second year. The best hybrid for GFY and DM was Rio-Grande; for FDN and FDA was Advance 2203; for GY was HT9150W and finally for TBP was Arrayan. Regardless of the hybrid used and the sowing season, production of maize depended on external factors such as maximum temperature and rainfall; therefore, producers need to consider sowing in spring to avoid the negative effect of high temperatures on plant development.

En condiciones de invernadero y durante el ciclo de invierno 2004 - 2005, se evaluaron dos híbridos de tomate (Lycopersicon esculentum Mill.) ‘Big Beef’ y ‘Miramar’ en tres sustratos: S1, vermicomposta + arena, en proporción 1:1 (v:v) + micronutrimentos quelatizados; S2, vermicomposta + arena, sin micronutrimentos; y el testigo S3, arena + solución nutritiva inorgánica. Los seis tratamientos se distribuyeron en un diseño completamente al azar con arreglo factorial 3 x 2 con 36 repeticiones, una planta por repetición. Se detectaron diferencias entre sustratos en rendimiento y calidad (P ≤ 0.01). El híbrido ‘Big Beef’ en el S3 presentó el rendimiento comercial más alto con 279 t ha-1, y superó al S1 con el mismo genotipo. En rendimiento de fruto total ambos híbridos crecidos en el S3 superaron al S1; sin embargo, el rendimiento en S1 fue mayor de 200 t ha-1 en ambos genotipos. Además, en S1 se logró mayor contenidode sólidos solubles y espesor del pericarpio en el fruto que en S3 y S2, por lo que el uso de vermicomposta + arena + quelatos puede ser una opción viable para producir tomate orgánico en invernadero.

Bitter-pit has been related to nutritional fruit unbalances, especially to calcium deficiency. In order to elucidate the nutritional and physiological processes that lead to a development of bitter-pit, a nutritional study of a Golden Smoothee/M9 apple orchard, endemically affected by bitter-pit has been carried out. An evaluation of bitter-pit incidence at harvest showed that only few apples had symptoms, but following two months under cold storage, more than 80% were affected. Mineral elements in leaves and fruits were analysed. As bitter-pit is associated with fruit size, the diameter and fresh and dry weight of fruits were recorded regularly, and the values fitted to sigmoid equation of growth, to calculate final size and maximum fruit growth rate. In terms of mineral nutrition, Nitrogen relates linearly to calcium and the ratio K/Ca in fruits increases along the season reaching a value of 41 at harvest time. A good correlation between leaf chlorophyll and fruit soluble carbohydrates was found.