Comparison of Experimental Methods to Assess the Competitive Ability of Weed Species

Abstract

Competition between crops and weeds interfere on growth and development with harm to one or both, in different ways. To quantify these differences in competition, additive and replacement series study methods are most often used, each with different characteristics and goals. Therefore, we aimed with this work to study inter-specific competition between plants of soybean and corn against the weeds Bidens pilosa (beggartick) and Digitaria insularis (sourgrass), by two experimental methods of study: additive and replacement series (substitutive) experiments. Initial tests were performed prior to the installation of replacement series experiments to describe the intra-specific competition features for all species. For additive experiments these are unnecessary. To compare the methods of study, there were two sets of trials (an additive and a substitutive) installed under greenhouse, during the growing season 2013/14. Variables analyzed were leaf area and dry weight of shoots of crops and weeds, at 50 days after emergence. The results were analyzed according to the methods used, these being compared. It was found that the additive method supplied results most prone to be applied in the field, while the replacement series (substitutive) method was more appropriate for studies that aimed to provide detailed scientific information regarding the proportions of plants and coefficients describing the behavior of the species community. L. Galon et al.2186

Competitive interaction between soybean cultivars and Sida rhombifolia

“…To test for differences in DRP and A, the null hypothesis was that the rates were equal to zero (Ho= 0); for TRP and RC, the rates were equal to one (Ho= 1); and for K, the rates of the differences between Kx and Ky were equal to zero [Ho= (Kx -Ky) = 0]. The criterion to consider the TRP and RP curves as different from those expected, was when the expected values (represented by dotted lines) were outside the confidence interval of 95% of the observed curves -solid and colored lines with confidence intervals in the same color (Galon et al, 2015a;Concenço et al, 2018). The criterion used to consider the RP and TRP curves different from the hypothetical straight lines was that at least in two proportions of the tested densities of the competing species they did not touch the colored lines, adapted from Bianchi et al (2006).…”

Allelopathic Effects of Bidens pilosa L. var. radiata Sch. Bip. on the Tuber Sprouting and Seedling Growth of Cyperus rotundus L.

“…and Raphanus sativus L. The results of paddy field experiments also demonstrated that phenolic compounds released from the BPr residues might cause the death of weeds [ 24 ]. On the other hand, it has been reported that BPr was capable of exhibiting competitiveness and reducing the crop yields of soybean and corn in both additive and substitutive competition experiments [ 25 ]. Wang et al [ 26 ] also indicated that BPr significantly suppressed the growth of Medicago sativa L. and Trifolium repens L. in substitutive competition experiments.…”

Competitive ability of soybean cultivars with Ipomoea indivisa

“…On the other hand, for the competitor, it was observed, in general, a lower CI with the increase in the density of soybean plants. The reduction in chlorophyll can compromise the photosynthetic activity of plants, normally observed in situations of abiotic (MANGENA 2018, IQBAL et al 2019 or biotic stress (GALON et al 2015). As a result, plants with a higher concentration of chlorophyll throughout their cycle usually obtain a higher dry matter (FREITAS FILHO 2014, GABARDO et al 2020).…”