Iranian Journal of Seed Research

Extended abstract
 Introduction: Management of agricultural operations in sugarcane fields should be informed by the accurate knowledge of sugarcane growth stages and phenology and is to be reviewed based on variety differences. Given the importance of emergence stage on the establishment of seedling and final quality and quantity of sugarcane yield and given the absence of respective information, a study was conducted to investigate the effect of different planting dates on the phenological characteristics of the seedling stage of sugarcane cultivars in the south of Khuzestan Province during 2016-17 and 2017-18.
 Materials and Methods: The experiment was carried out as a randomized complete block design with three replications. In terms of growth period length, Very premature, Premature, and Semi mature cultivars included CP73-21, CP57-614 and CP69-1062. Planting dates were Aug. 11^th, Aug. 23^rd, Sep. 1^st and Sep 11^th. Planting operation was conducted manually and with 1/3 overlap of grafts. In order to prevent the negative effects brought about by the dispersion and non-uniformity of the experimental field and the special conditions of sugarcane cultivation, each cultivar was cultivated in a separate field and after sampling and the study of different traits, the statistical analysis of each cultivar was performed separately.
 Results: The results showed that sugarcane seedling was not affected by annual conditions and the interaction effect of annual conditions and planting dates. The significant differences of planting dates were observed at the beginning of emergence, its completion and rate of emergence and the number of leaves produced and their area. The fastest rate of the beginning and the completion of emergence was obtained in CP73-21, and on different planting dates, it was more permanent than other cultivars studied, while CP69-1062 had the slowest and more behavioral diversity of emergence on different planting dates. The cultivar CP73-21 did not produce good results in terms of leaf area, but the CP69-1062 cultivar was able to produce the highest level of leaf area due to the extra number of leaves and the mean value of a single leaf area. In addition, the best results were obtained in all characteristics in August, followed by September.
 Conclusions: Based on the results, in order to achieve the best emergence of sugarcane buds, it is necessary to complete the cultivation of most of the fields within the first twenty days of the beginning of the planting season and priority should be given to cultivar CP69-1062 and then cultivars CP57-614 and CP73-21. Due to the differences between sugarcane cultivars, utilizing seedling stage growth data can lead to more scientific management of the crops in terms of the characteristics of each cultivar, which eventually leads to desirable yields.
 
 
Highlights:

Extended Abstract
Introduction: Plants release much of bioactive chemicals from different parts such as leaves, stems and roots through different mechanisms to their surrounding environement. These biologically active chemicals are often referred to as "allelochemicals". Allelopathic compounds play a major role in reducing germination and the growth of crops.
Materials and methods: In this study, the effect of leaching on the reduction of phytotoxicity effect of soybean, black cumin, dragonhead and dill was investigated on the emergence and early growth of canola (Brassica napus L.). The experiment was conducted as factorial based on a completely randomized design with four replications in 2016. Treatments included four previous crop residue (soybean, black cumin, dragonhead, and dill), and three levels of leaching (without leaching, one-time leaching, and two-times leaching). The leaching-free treatment (control) was sub-irrigated to maintain the uniformity of environment moisture. Five days after the first leaching, the two leaching treatment was irrigated again. Five days after the second leaching, when the soil moisture was suitable for seed planting, 10 seeds of canola were cultivated in each pot at a depth of 3 cm of soil. After three weeks seedlings of canola were removed from the pot and the traits were measured.
Results: The results showed that the growth characteristics of canola, except root length, were affected by the residues of the previous crop. In non-leaching conditions, the residue of the four plants reduced the rate and amount of canola emergence, and the greatest reduction in canola emergence was recorded for the application of black cumin residue (7.5%). In the leaching conditions, the length of canola leaves increased, which was higher in the twice leaching treatment. This trend shows that as the amount of leaching frequency increased, it is highly likely that more inhibitiing materials leave the soil and conditions become suitable for canola germination and growth.. The highest dry weight of canola root was observed in one-time leaching treatment. The dry weight of canola leaf grown in dill and soybean residues was increased as a result of one-time leaching, whereas the dry weight of canola grown in black cumin and dragonhead residues showed a higher increase in two-times leaching. Results show that four studied plants have canola growth inhibiting compounds and leaching can ameliorate this effect. The response of canola in the soil containing black cumin and dragonhead residues is higher in two-times leaching, and in the soil containing plant residues dill, one-time leaching is sufficient. In soils containing soybean residue, the response index was almost similar in case of one and two-times leaching.
Conclusion: Generally, the results showed that the application of leaching before planting canola reduced the inhibitory effects of plant residue on germination and growth of canola. Therefore, it is suggested that in the agricultural ecosystems in which canola is present in crop rotation, cultivation of canola must be avoided in presence of soybean, black cumin, dragonhead, and dill residue to eliminate their inhibitory effects on canola growth. In areas with water restriction, autumn rainfall can act as leaching and reduce the effect of allelopathic compounds. In case leaching is not possible, cultivation of canola inside the residue of these plants must be avoided.
 
 
Highlights:
1-Leaching can reduce the effect of allelopathic compounds.
2- Allelopathic compounds of some plants such as black cumin showed better response to two-times leaching.