The use of eco-friendly mulch materials as alternatives to the standard polyethylene (PE) has become increasingly prevalent worldwide. Consequently, a comparison of mulch materials from different origins is necessary to evaluate their feasibility. Several researchers have compared the effects of mulch materials on each crop variable through univariate analysis (ANOVA). However, it is important to focus on the effect of these materials on fruit quality, because this factor decisively influences the acceptance of the final product by consumers and the industrial sector. This study aimed to analyze the information supplied by a randomized complete block experiment combined over two seasons, a principal component analysis (PCA) and a cluster analysis (CA) when studying the effects of mulch materials on the quality of processing tomato (Lycopersicon esculentum Mill.). The study focused on the variability in the quality measurements and on the determination of mulch materials with a similar response to them. A comparison of the results from both types of analysis yielded complementary information. ANOVA showed the similarity of certain materials. However, considering the totality of the variables analyzed, the final interpretation was slightly complicated. PCA indicated that the juice color, the fruit firmness and the soluble solid content were the most influential factors in the total variability of a set of 12 juice and fruit variables, and CA allowed us to establish four categories of treatment: plastics (polyethylene - PE, oxo- and biodegradable materials), papers, manual weeding and barley (Hordeum vulgare L.) straw. Oxobiodegradable and PE were most closely related based on CA.

Mulch materials of different origins have been introduced into the agricultural sector in recent years alternatively to the standard polyethylene due to its environmental impact. This study aimed to evaluate the multivariate response of mulch materials over three consecutive years in a processing tomato (Solanum lycopersicon L.) crop in Central Spain. Two biodegradable plastic mulches (BD1, BD2), one oxo-biodegradable material (OB), two types of paper (PP1, PP2), and one barley straw cover (BS) were compared using two control treatments (standard black polyethylene [PE] and manual weed control [MW]). A total of 17 variables relating to yield, fruit quality, and weed control were investigated. Several multivariate statistical techniques were applied, including principal component analysis, cluster analysis, and discriminant analysis. A group of mulch materials comprised of OB and BD2 was found to be comparable to black polyethylene regarding all the variables considered. The weed control variables were found to be an important source of discrimination. The two paper mulches tested did not share the same treatment group membership in any case: PP2 presented a multivariate response more similar to the biodegradable plastics, while PP1 was more similar to BS and MW. Based on our multivariate approach, the materials OB and BD2 can be used as an effective, more environmentally friendly alternative to polyethylene mulches.

O nitrogênio (N) é um nutriente importante para a produção de melão (Cucumis melo L.), porém existe pouca informação sobre a quantidade necessária para se obter um balanço entre o crescimento e a produtividade. Os órgãos vegetativos do melão precisam se desenvolver suficientemente para interceptor luz, acumular água e nutrients, mas também é importante alcançar uma grande relação de massa seca produtiva-vegetativa para maximizar a produção de frutos. Investigou-se a influência de quantidades de N no crescimento, na produção de matéria seca e na produtividade do melão tipo 'Pele de sapo'. Foi conduzido experimento com três anos de duração, de maio a setembro, com irrigações de 100% da evapotranspiração e 11 doses de adubação de N, no intervalo de 11 a 393 kg ha-1 em três anos. A produção de massa seca de folhas e caules aumentou com o aumento das doses de N. A matéria seca da planta toda foi afetada de maneira semelhante, enquanto a dos frutos decresceu com o aumento de N acima de 112, 93 e 95 kg ha-1, em 2005, 2006 e 2007, respectivamente. O índice de área foliar máxima (LAI) mais aulto (3.1) foi obtido com a dose de 393 kg N ha-1de N. A dose mais baixa de N reduziu a produtividade de frutos em 21%, enquanto a dose mais alta aumentou o crescimento vegetative, LAI e a duração de área foliar (LAD), mas reduziu a produtividade em 24% em relação ao tratamento N93. Aplicações excessivas de N aumentam o crescimento vegetativo às expensas do crescimento vegetativo. Para este tipo de melão, doses da ordem de 90-100 kg ha-1 de N são suficientes para crescimento adequado e produção máxima. Para obter produções próximas ao máximo, a concentração de N na folha no final do ciclo da cultura não deve ser maior que 19.5 g kg-1.

Nitrogen (N) is an important nutrient for melon (Cucumis melo L.) production. However there is scanty information about the amount necessary to maintain an appropriate balance between growth and yield. Melon vegetative organs must develop sufficiently to intercept light and accumulate water and nutrients but it is also important to obtain a large reproductive-vegetative dry weight ratio to maximize the fruit yield. We evaluated the influence of different N amounts on the growth, production of dry matter and fruit yield of a melon 'Piel de sapo' type. A three-year field experiment was carried out from May to September. Melons were subjected to an irrigation depth of 100% crop evapotranspiration and to 11 N fertilization rates, ranging 11 to 393 kg ha-1 in the three years. The dry matter production of leaves and stems increased as the N amount increased. The dry matter of the whole plant was affected similarly, while the fruit dry matter decreased as the N amount was increased above 112, 93 and 95 kg ha-1, in 2005, 2006 and 2007, respectively. The maximum Leaf Area Index (LAI), 3.1, was obtained at 393 kg ha-1 of N. The lowest N supply reduced the fruit yield by 21%, while the highest increased the vegetative growth, LAI and Leaf Area Duration (LAD), but reduced yield by 24% relative to the N93 treatment. Excessive applications of N increase vegetative growth at the expense of reproductive growth. For this melon type, rates about 90-100 kg ha-1 of N are sufficient for adequate plant growth, development and maximum production. To obtain fruit yield close to the maximum, the leaf N concentration at the end of the crop cycle should be higher than 19.5 g kg-1.