No abstract

The critical time for weed removal (CTWR) is a period in the crop growth cycle when weed control must be initiated to prevent yield losses. Knowing the CTWR is useful for making decisions about the timing of weed control and in achieving efficient herbicide use from both biological and economic perspectives. Field studies were conducted in 2008 and 2009 at three locations in Serbia and one location in the USA to determine the CTWR in imidazolinone (IMI)-resistant sunflower grown with and without application of pre-emergence (PRE) herbicide. A four-parameter log-logistic model was fitted to data relating relative crop yield to increasing duration of weed presence. The CTWR without PRE herbicide treatment ranged from 14 to 26 d after emergence (DAE) corresponding to the V3 (three leaves) to V4 stages compared to 25 to 37 DAE, which corresponded to the V6 to V8 stages with PRE herbicide. The CTWR in IMI-resistant sunflower grown with PRE herbicide can be delayed by an additional 6 to 12 d compared to the crop grown without PRE herbicide under the present experimental conditions. The practical implication of this study is that the use of PRE herbicide could extend post-herbicide treatments by another 6 to 12 d with respect to the critical time required for weed removal without PRE herbicide in IMI-resistant sunflower.

The effects of three tillage systems: no-tillage (NT), reduced tillage (RT) and conventional tillage (CT), and three levels of fertilization (0, 258 and 516 kg/ha NPK (58:18:24)), on the maize yield during ten years (1999)(2000)(2001)(2002)(2003)(2004)(2005)(2006)(2007)(2008) were analyzed on the chernozem soil type in Zemun Polje, Serbia. Statistical analyses showed significant effects of all three factors i.e., year, soil tillage and amount of fertilizers, and their interactions on the maize yield. The ten-year averages showed that the highest yields were observed with CT (10.61 t/ha), while the averages with RT and NT were lower (8.99 t/ha and 6.85 t/ha, respectively). The results of the influence of the amount of the applied fertilizers on maize yield showed that the lowest yield was in the zero level of fertilization 7.71 t/ha, while the yield was raised when the 258 kg/ha and 516 kg/ha NPK were applied (9.18 t/ha and 9.56 t/ha, respectively). Analyzing the influence of the soil tillage systems on maize production with respect to the amounts of applied fertilizers, this research revealed the benefits of CT under the presented agroecological conditions, irrespective of the level of applied fertilizer.

A soil tillage system adjusted to the soil type and agro-ecological conditions, together with the optimal nutrient supply, is a prerequisite for high maize (Zea mays L.) yield. However, there is little knowledge about the influence of soil tillage and nitrogen (N) rates on maize grain quality. A study was initiated in 1978 in Zemun Polje, Belgrade, Serbia, on the chernozem soil type. The effects of three N rates—0, 180 and 240 kg N ha−1—within three tillage practices—no-tillage, reduced and conventional tillage—and their influence on grain yield (GY) and the content of proteins, starch, oil, total tocopherols and carotenoids, phytic phosphorus (Phy), glutathione (GSH), phenols and inorganic P (Pi) in maize grain were analysed in the period 2016–2018. Differences in maize GY were 2.57 and 3.01 t ha−1 for reduced- or no-tillage, respectively, in comparison to conventional tillage. Conventional tillage and higher N rates contributed to the increase in maize yield and the grain nutritional quality with regard to the increased level of proteins, GSH and Phy. On the other hand reduced inputs were beneficial only for grain quality, in relation to the increase in tocopherols and phenols.

This study concerned the effect of different intercropping systems (alternating rows and alternating strips) of maize and soybean compared with single cropping, in combination with different fertilisers (biofertiliser, organic fertiliser, and urea) on the potential availability of magnesium (Mg), iron (Fe) and zinc (Zn) from grain, through their ratio with phytate (as inhibitor) and β-carotene (as promoter). The higher grain yield and land equivalent ratio obtained under alternating rows + biofertiliser treatment demonstrated the improved ability of crops in close proximity for better utilisation of existing agro-ecological conditions. Alternating rows + organic fertiliser decreased the molar ratios phytate : β-carotene, phytate : Fe, phytate : Mg and phytate : Zn, indicating increased availability of the mineral elements in both crops. However, alternating strips + organic fertiliser contributed mostly to an increase in β-carotene, Mg, Fe and Zn concentrations in soybean. Increased grain yield of both crops was followed by decrease in β-carotene and increase in phytate, particularly in maize. In soybean, β-carotene could be considered as the main contributor to Fe availability. Accordingly, cropping in alternating rows or strips, combined with biofertilisers, could serve as fortification measures for improved nutritional quality of maize and soybean grain, without grain yield losses.

Herbicide application in seed maize requires special attention due to their larger sensitivity than hybrid maize. The aim of study was to examine and define the sensitivity/tolerance of the five maize inbred lines with different susceptibility to herbicides (belonging to different heterotic groups), based on alterations of secondary metabolites (phenolics, protein sulfhydryl groups, phytic and inorganic phosphorus). Two groups of herbicides: triketons (mesotrione and topramezone) and sulfonylureas (rimsulfuron and foramsulfuron) were tested. Lines from independent heterotic group, which were sensitive to herbicides expressed visible damages together with significant reduce in grain yield, mainly induced by sulfonylurea herbicides. Parallel with that, significant increase in phenolics, phytic and inorganic phosphorus, as well as drop in protein sulfhydryl groups were observed in their leaves. Tolerant lines (belonging to Lancaster group) had mainly insignificant grain yield reduce, also with lesser variations in sulfhydryl groups, content of phytic and inorganic phosphorus, as well as increase in phenolics content. Among examined secondary metabolites, phytate is the main factor, contributing to herbicide tolerance in maize lines. Owing to lesser yield decrease and variation in content of examined secondary metabolites, expressed in treatments with triketone herbicides, they usage could be safe in maize lines. [Projekat Ministarstva nauke Republike Srbije, br. TR 31068]

A field experiment was conducted in order to estimate the influence of different arrangement patterns of maize plants (Zea mays L.) in combination with low rates of herbicides on weed infestation and on production parameters of the crop. The maize was sown at 70-, 50-, and 35-cm row space with the same crop density. The weed biomass declined with smaller row spaces and was, on average, the lowest with the 35-cm row space; even though the arrangement patterns of the maize plants had no significant effect on the average values of the weed biomass. The interaction of the arrangement pattern and the herbicide rate significantly influenced weed biomass. Maize grain yield expressed the greatest variation under the effects of applied factors, but did not differ significantly between treatments with the full and the half rate of herbicides. The results indicate that it is possible to control weed infestation level if maize is grown with increased spatial uniformity and combined application of other practices such are herbicides. In such a way, maize plants are more competitive against weeds and even lower amounts of herbicides could be applied in order to achieve high yields.    

The chemical method of weed control is an indispensable step in cropping practices of sweet maize. Application of the herbicides can induce the abiotic stress which affects the non-enzymatic antioxidants in the crops, especially on the sensitive one, like sweet maize is. Antioxidant profile, through the measurement of the soluble phenolic, carotenoids, phytic acid and glutathione concentration, in the grain of the three sweet maize hybrids after application of herbicides, foliar fertilizer, as well as their combinations, in field experiment, conducted over a two-year period, was determined. The content of tested antioxidant parameters was dependent on hybrids, growing season, as well as of the applied treatment. Sulfonylurea herbicides significantly increased the antioxidant status of sweet maize fresh grain, compared to the herbicide from triketone group, without affecting the fresh grain yield. Combination of herbicide plus foliar fertilizer expressed a various impact on antioxidant profile of the maize grain. Furthermore, significant correlations (positive and negative) between fresh grain yield and analyzed antioxidants in grain of three sweet maize hybrids were noticed.