Cover crops (CC) are an important low-input strategy in sustainable agricultural systems. The impact of different CC (common vetch, field pea, winter oats, fodder kale, common vetch + winter oats and field pea + winter oats), organic mulch, control treatment-fallow, and bio-fertilizer (BF) application, on yield and quality of sweet maize kernel was evaluated. CC biomass was higher in mixtures: field pea + winter oats, and common vetch + winter oats, as well as in fodder kale. Kernel yield and its chemical composition varied significantly by CC, BF, year, and their interaction. Organic mulch enhanced the concentration of sugars and glutathione in maize kernel. BF increased kernel yield, the concentration of sugars, vitamin C, Mg, Fe, Zn, and reduced phytate concentration. The highest Mg and Mn concentration in maize kernel was achieved with fodder kale, Zn concentration with common vetch + winter oats + BF, and Fe concentration with winter oats. The same treatments expressed the highest impact on variability in concentration of the phytate, phenolics, and yellow pigment, thus affecting further bio-availability of essential elements. Results indicate that in a semi-arid climate, under rain-fed conditions, CC such as fodder kale and winter oats + common vetch could enhance sweet maize productivity and kernel quality, serving as an important part of a sustainable cropping system, to facilitate food security.

The evaluation of pumpkin (Cucurbita maxima Duch.) and maize (Zea mays L.) intercropping productivity, under different farming systems: conventional farming vs. conservation farming was carried out on the chernozem type of soil at Zemun Polje, Serbia. Results obtained by the bivariate analysis of variance showed significant differences between different proportions of components in intercropped maize and pumpkins. Regarding the land equivalent ratio (LER), two rows of pumpkins and two rows of maize (proportion 2/3:1/3) were the optimum spatial arrangement in conventional farming system, while proportion 1/3:2/3 was optimal in conservation farming system. The yield of pumpkins proportionally increased with the increase of the plant population, although the intraspecies competition of pumpkins was very pronounced in intercropping with maize. The average fruit yield of pumpkins in the first year was lower in conservation farming practices in comparison with conventional farming practices. On the other hand, situation was complete opposite with pumpkin yield in second year of investigation, while significant decrease in maize yield was observed in the plots where conservation farming practices were applied. Growing pumpkins in mixture with maize probably costs a small farmer very little more effort, than the production of a sole stand of maize. At least where the productivity of mixture is dominated by one species, as with maize in maize-pumpkins intercropping, the competitive effect of the recessive species on the dominant is small.

The study was conducted in the experimental field of the Maize Research Institute Zemun Polje, Serbia, during 2013/14-2014/15. The experiment was established as a block design with four replications. As winter cover crops-CC (factor A) the following plants were grown: CV-common vetch (Vicia sativa L.), FP-field pea (Pisum sativum L.), WO-winter oats, (Avena sativa L.), FK-fodder kale (Brassica oleracea (L.) convar. acephala), two mixture variants of legume crops with oats (CV+WO and FP+WO) and two control treatments: a variant in which the surface was covered with dead organic mulch (DOM) and traditional variant: after ploughing in the fall plot stayed uncovered during the winter (TV). Green biomass of the cover crops was incorporated in the soil, immediately after, half of the elementary plot was infested with bio-fertilizer (BF) -Uniker (mobilizer of nutrients) in an amount of 10 l ha -1 (factor B), which contains the strains of cellulolytic and proteolytic bacteria to support the mineralization of entered crop residues. The seeds of sweet maize 'ZPSC 421su (FAO 400) were sown at the arrangement of 70 cm between rows and 22 cm between plants in the row (65,000 plants per ha). Preceding crop in both years was winter wheat. The kernel protein content was measured on infrared analyser. The data were processed by ANOVA. The investigated factors (CC and BF) showed significant effect on protein content in sweet maize kernel in both years. As it was expected, the greatest impact on protein content was exhibited in leguminous species grown alone, or in mixtures with oats, particularly in the dry, 2015. Small grains intercropped with legumes obtained higher values of protein content than small grain grown as monocrops.