Effect of Fertilization on Weed Infestation, Morphological and Productive Traits of Different Alternative Small Grains

﻿ This examination aims to determinate influence of fertilizers toward  weed infestation, morphological and productive traits of different  alternative small grains, as well as to examine the correlation of the  studied traits of alternative small grains with weed infestation in  organic production. The field experiment was conducted on luvic  chernozem in completely randomized blocks, repeatad four times, in  the three year period (2013/2014-2015/2016). Examination was  carried out on one winter cultivars of naked barley, spelt, durum,  compactum wheat and triticale, and the experiment included  fertilization with microbiological fertilizer (5.0 L ha-1) as well as the  combined application of microbiological (5.0 L ha-1) and organic  fertilizer (3.0 t ha-1). Results obtained pointed out that examined  factors have important influence toward number and the dry weed  weight, but the influence toward diversity weeds is negligible. The  smallest the total number of weeds (12.7 plants m-2), as well as the  dry weight of weeds (18.5 g m-2) was noted in the spelt (P˂0.01).  The considerably significant smaller the total number of weeds on  the variant F2 (14.7 plants m-2) compared to F1 (15.4 plants m-2) and  F0 (15.5 plants m-2), while dry weed weight on the variants F1 (23.7  g m-2) and F2 (23.8 g m-2) significant higher comparing to control F0  (20.7 g m-2). The use of fertilizers have significatly influenced the  increase of the stem height (5.5-10.0%), spike length (6.4-9.9%),  weight of the plant (9.5-20.8%) and the weight of grains in the spike  (7.8-16.9%). The negative dependence of the weeds number  (r= -0.69) and its dry weight (r= -0.39) relаted to the height of  stem, and, also, negative dependence between weight of grains in  the spike with the weed number (r= -0.32) has been perceived.  These results of examination showed that proper selection of the  genotypes with the application of fertilisers could have a significant  effect on the weeds in the organic production alternative small  grains.


Introduction
The selection of species and cultivars of cereals suitable to specific conditions of organic agriculture demands different approach comparing to that used in conventional and intensive system of production (Przystalski et al 2008;Roljevic Nikolic et al 2018). This is because there are fewer opportunities in organic production to compensate for yield decrease caused by diseases, low nutrient levels, and weeds . An important part of the weed control strategy in the organic production system is the selection of cultivars that compete with weeds for limited resources, produce exudates that inhibit growth of weeds and reduce economic losses by maintaining a high level of grain yield (Andrew et al 2015). During the last three decades the significant development was achieved in understanding the morphological and physiological traits of cereals which provide foundation for their competitive ability against weeds. Examinations conducted globally are pointing toward those cereal`s cultivars with fast initial growth, height of stem, large leaf surface and intensive tillering, to be the most competitive. It is determined that such a varietes are reducing the photosyntetic active radiation through their above-ground parts, creating shade for weeds and thus reducing their biomass and number 407 (Korres & Froud-Williams 2002;Vandeleur & Gill 2004;Mason et al 2007;Zerner et al 2016). Therefore, the imperatives in organic production is knowledge of crop characteristics in order to establish stable production.
Apart from genotype, soil fertility and availability of nutrients can also affect the diversity and dynamics of the weed community (Jornsgard et al 1996;Blackshaw et al 2005). Garcia-Martin et al (2007) have noted that by reducing the availability of nutrients in the initial stages of vegetation, weeds are placed in an extremely unfavorable position in relation to crops, and in this respect organic sources of nutrients can have an impact on the weed community.
On the other hand, some studies conducted with mineral fertilizers have shown that higher levels of their application positively affect the seed germination (Jornsgard et al 1996) and the weed number (Ross & Van Acker 2005), and that the mineral fertilization have a stimulating effect on weed infestation. When it comes to weed biomass, Jornsgard et al (1996) state that weed biomass in winter wheat could be increased, unchanged, or reduced with increased soil N depending on weed and crop. The aim of this research is to determine if in the terms of organic production, the use of fertilization might influence weed infestation, morphological and productive traits of alternative small grains, simulatenously, investigate connection between traits of different alternative small grains and the weed infestation.

Material and Methods
This research was carried out on "Radmilovac" (44 o 45'N, 20 o 35'E Serbia) experimental field of the Faculty of Agriculture in Belgrade, during the period 2013/2014-2015/2016. The average annual air temperature in this period was 12.7 °C, while the average rainfall was 670.6 mm.
A two-factor field trial was arranged using the completely randomized blocks was employed in four replications, with the area of the elementary plot amounting to 6 m 2 . The soil type was luvic chernozem (WRB 2014), with the following characteristics: pH-(H2O) 8.04, total content of N 13%, available forms of phosphorus 22.18 mg P2O5 100 g -1 dry weight and potassium 19.10 mg K2O 100 g -1 dw, content of humus in the topsoil layer 2.45%. Winter cultivars of different alternative small grains are grown in four crop rotation: maize → winter wheat → spring barley+red clover → red clover. Previous crop was maize (Zea mays L.) in all three seasons.
Tillage method with the plough was carried out at a depth of 25 cm, from 15-20 October during all three years. Presowing preparation was carried out by disc harrow and harrow. The sowing was done manually, from 20-25 October.
Weeds were cut and roots discarded. The weight was measured (g m -2 ) in fresh, and after drying in natural conditions, along with the weight in air dry condition. Measures for weed suppression were not carried out.
During all three years of examination, seven to ten days before harvest, 10 plants were randomly sampled in order to determine the morphological and productive traits of all alternative small grains in each variant of fertilization. The 408 Journal of Agricultural Sciences (Tarım Bilimleri Dergisi) 26 (2020) 406-414 following parameters were measured: (1) the stem height to the spike (cm), (2) the length of the spike (cm), (3) the weight of stem and the spike-weight of plants (g), (4) the weight of grains per spike (g).
Data processing was performed in Statistica statistical package. A method for analyzing variance (F test) for dual factor examination was used, and the significance of differences between treatments was tested with the LSD test at significance level P˂0.01 and P˂0.05. The method of simple linear correlation and regression analysis was used to examine the dependence between the parameters tested.

Floristic composition of weed community of diferent alternative small grains in organic production
After the observation during this three-year period, it can be concluded that a weed community consists of relatively large number of species (26) in alternative small grains, representing one of organic field production characteristics. Annual weeds make 61.5%, and perennial 38.5% of the total number of recorded species. According to Koocheki et al (2009), in organic and rational crop cultivation systems, perennial weeds account for 66% and 56% of the total weed population, while in intensive crop cultivation systems they are significantly lower. During all three years of the examined period, preceding crop was maize (Zea mays L), row crop, thus explaining the higher representation of annual weeds. The most prevalent annual weed are Stellaria media (L.) Vill., Veronica persica Poir., Capsella bursa pastoris L., and perennial Agropyrum repens L., Lepidim draba L. and Convolvulus arvensis L. (Table 1). These weed species infestate a lot of various crops, particularly cereals and row crops. The proper selection of species and cultivars of crops is an important part of the strategy in the action against weeds, especially in production systems characterized by reduced protection (Andruszczak et al 2012;Andrew et al 2015). The results of the study have shown that the genotype has a slight influence on the diversity of the weed community in conditions of organic production. Only statistically significant differences in the number of perennial weeds were established, whereby it is with the spelt (0.9 species m -2 ) significantly lower compared to triticale (2.0 species m -2 ) and compactum wheat (1.8 species m -2 ) ( Table 2). Examining the impact of different tillage methods on the weed community in organic production Sans et al (2011) have established a smaller share of perennial weeds in the crop of spelt compared to common wheat. Research conducted by other authors is also indicative of the lesser weed infestation of spelt compared to other cereals (Szewczyk 2013).

Table 2-Weed infestation of winter cultivars various cereals
On the other hand, the number of weeds and their dry weight was significantly influenced by investigated factors as their interaction is producing significant effect (Table 3). The results indicate significant differences between the alternative small grains in the number of weeds, with the largest number being recorded in durum wheat (16.7 plants m -2 ) and the lowest in spelt (12.7 plants m -2 ) ( Table 2). A significant influence of fertilization on the total number of weeds was determined, whereby it smaller on the variant F2 (14.7 plants m -2 ) compared to F1 (15.4 plants m -2 ) and F0 (15.5 plants m -2 ) (P˂0.05). In these production conditions, the GxF interaction showed a very significant impact on the number of weeds, which was most pronounced in triticale, as the number of weeds on varieties F1 and F2 was 26.2% and 15.3% lower compared to control. On the other hand, in naked barley and durum wheat number of weeds at F1 variant was significantly higher in comparison with the F0 (21.3% and 11.4%), while in spelt and compactum wheat the obtained differences between the variants of fertilization were not significant.
During the examination of weed infestation among crops of winter spelt wheat cultivars grown under different conditions of mineral fertilization and chemical plant protection, Andruszczak et al (2012) have underlined that application of higher rates of mineral fertilizers have slightly increased the number of weeds. Similar results are noticed by other authors (Jornsgard et al 1996).
The analysis of the variance of dry weeds weight indicates that there are very significant differences between the investigated genotypes (Table 3). The highest dry weight of the weed was recorded in durum wheat (26.2 g m -2 ), and the lowest in the spelt (18.5 g m -2 ) ( Table 2). A large dry weight of the weed recorded in the cv. Dolap was expected, given the origin of durum wheat and its adaptation to a warmer climate with less precipitation (Kaya & Turkoz 2016). Fertilization is a factor that significantly affects the weeds weight (Table 3). Very significant differences were found between control (20.7 g m -2 ) and fertilization variants (23.7 g m -2 and 23.8 g m -2 ) ( differences between fertilization variants in the examined alternative small grains were significant (GxF) ( Table 2 and  Table 3). The largest differences were found in the compactum wheat and spelt, wherein the dry weight of the weed on the F1 variant was higher by 61.0% and 48.8%, while in the variant F2 to 85.3% and 109.9% compared to control. Significantly lower dry weight of the weed on varieties with applied fertilizers compared to control was recorded only in hard wheat (28.9% and 15.3%). On the other hand, some authors have not noticed significant differences in the biomass of weeds between different levels of mineral fertilizers, because in such circumstances it was dependent on both crops and the types of weeds (Jornsgard et al 1996;Andruszczak et al 2012).

Morphological and productive traits of different alternative small grains in organic production
The height of the stem, as well as the overall height of the plant, represents an important traits for cereals, significantly influencing the formation of total yield (Zerner et al 2016). In the framework of the investigated alternative small grains, the spelt is distinguished by the highest stem (94.2 cm) and the longest spike (10.3 cm). The largest plant weight and grain weight in the spike were recorded in triticale, cv. Odisej (4.1 g and 1.6 g). On the other hand, the weight of the plant (2.0 g) and the grain weight in the spike (0.9 g) of naked barley (cv. Golijat), is significantly lower compared to other genotypes (Table 4).
Significant differences in the investigated traits were also established between fertilization variants. The use of fertilizers significantly influenced the increase in the height of the stem (5.5-10.0%), the length of the spike (6.4-9.9%), the plant weight (9.5-20.8%) and the grain weight in the spike (7.8-16.9%), in particular the variant F2. Jablonskytė-Raščė et al (2013) have found that the combined application of organic fertilizer and bio-activators significantly affects the length and weight of spike of common and compactum wheat. Significantly higher weight of grains per spike wheat on intensively fertilized treatments was obtained by Jaćimović et al (2008). Although the GxF interaction did not have a significant impact on the examined morphological and productive traits, the application of fertilizers showed a positive effect on all types of alternative small grains. The best effect of fertilization on the stem height, the weight stem and length, as well as the weight of grains per spike was found in the compactum wheat, while the biggest difference between fertilization variants in the spike length was recorded in the naked barley.

Correlation and regression analysis
The results of the correlation analysis indicate a positive correlation between the morphological and productive properties of alternative small grains (Table 5). In addition, the negative correlation between the height stem and the number of weeds m -2 (-0.69), as well as the dry weeds weigh (-0.39) is noticed. Regression analysis is often used biostatistik technique in plant breeding (Pakize et al 2015). Based on the regression equation, it was found that the increase in the height stem by 1 cm leads to a decrease in the number of weeds for 0.11 plants m -2 (ŷi= 23.77-0.11* xi) and the dry weed weight for 0.16 g m -2 (ŷi= 34.86-0.16* xi). The dependencies between the parameters examined were very significant, which was determined by testing the obtained coefficients of simple linear correlation: the dependence of the number of weeds on the height stem (r= -0.69) and the dependence of dry weight of weeds on the height stem (r= -0.39). In the tests of some authors (Korres & Froud-Williams 2002;Konvalina et al 2007;Hoad & Davies 2008) it is affiliated that cultivars with high stem reduce the penetration of photosynthetic active radiation to lower levels, whereby the weeds become shadowed, and consequently their number and biomass decrease in relation to shorter cultivars of cereals. Thus, the shorter cultivars are less suitable for organic production (Mason et al 2007). Also, a negative correlation relationship between the number of weeds and the grain weight in the spike (-0.32) was established, where the regression equation showed that by increasing the number of weeds per 1 plant m -2 the grain weight in the spike decreases by 0.04 g (ŷi= 1.999-1.041 * xi). By testing the linear correlation coefficient, a statistically significant dependence was found between these two parameters (r= -0.32). In organic wheat production 412 Journal of Agricultural Sciences (Tarım Bilimleri Dergisi) 26 (2020) 406-414 negative correlation of weed biomass with productive cereal properties has been determined (Mason et al 2007;Roljević Nikolić et al 2017).

Conclusions
The results of this study showed that in the organic alternative small grains production the use of proper fertilization and selection of the cultivars with adequate morphological and productive traits, might create significant influence on the number and dry weight of weeds, while the impact on the diversity of the weed community is negligible. In addition, the application of the examined fertilizer variants has a very positive effect on the studied morphological and productive properties of grain. A negative correlation between the stem height and the number (-0.69) and dry weight of weeds (-0.39) was established. Consequently, the smallest number (13.7 plants m -2 ) and dry weight of weeds (18.5 g) were recorded in the spelt, which has the highest stem (94.2 cm) within the investigated cultivars. The obtained results indicate that the height stems has a significant contribution to the suppression of weeds. On the other hand, the weight of grains per spike depends on the number of weeds (-0.32), which indicates that the mechanisms that contribute to control and suppression of weeds is of key importance for the establishment of stable production in organic agriculture.