Forage Yield and Quality Characteristics Evaluationof two Rapeseed Genotypes (Brassica napus) to Different Irrigation Interruption Levels and Plant Density

Abstract
This research was done in the form of random complete block statistical design using split-factorial method with three replications in Agricultural Sciences and Natural Resources University of Khuzestan in the year 2022-2023. Three controltreatment, interruption of irrigation at the beginning of flowering until 50% of podding and interruption of irrigation at the podding stage until harvest were compared in the main plots.Two genotypes of Hyola 4815 and Aram and three densities of 80, 110 and 140 plants.m^-2 were investigated in sub-plots. The results showed that the interaction of irrigation_*genotype_*density on the number of ranches, insoluble content in acidic detergent, ash, digestible dry matter, lactation specific energy and metabolizable energy was significant. The highest and lowest content of insoluble fibers was obtained from the control treatment, density of 140 plants and Hyola4815 genotype, and interruption of irrigation, density of 80 plants per square meter and Aram genotype, which showed a significant difference with other treatments. gave In general, the highest dry forage yield was obtained in the full irrigation treatment (3722 kg.ha^-1), which showed a significant difference with the other levels of irrigation. Also, the Aram genotype showed a significant superiority with fodder yield equal to 3482 kg.ha^-1 compared to Hyola 4815 genotype. The highest and lowest yield of dry fodder (respectively 3471 and 3226 kg.ha^-1) was related to the density of 140 and 80 plants, respectively, which had significant differences with each other, but did not show significant difference with the density level of 110 plants.m^-2. Based on this, in addition to the Aram genotype as the superior genotype, the plant density of 110 plants per square meter can be considered as the superior density in this experiment, which, in addition to the higher forage quality, also has a lower seed consumption cost compared to the density of 140 plants per square meter.
Introduction
Irrigation is one of the most important factors affecting the quality and quantity of fodder plants. Also, the digestibility of fodder depends on the chemical composition of fodder. Plant density is a factor that affects the distribution of plant dry matter. In the study of Nasirpour and Zakirnejad (2018), the effect of four densities of 20, 30, 40 and 50 plants per square meter on the yield of pearl millet fodder was investigated and the results showed that the highest yield of millet fodder was obtained at a density of 50 plants per square meter and the lowest at a density of 20 The plant was obtained in square meters. Also, the research findings of Eskandari et al. (2017) increased the yield of dry fodder and the amount of hemicellulose-free cell wall with the increase in corn plant density, and then the forage quality was estimated to be higher. The presence of water-rich and profitable plants such as corn, whose cultivation has been developed regardless of water resource limitations in all provinces, is one of the reasons for the lack of attention to plants such as canola, which can be used as grazing, storage and silage for livestock. On the other hand, the scientific investigation of the fodder aspects of rapeseed has remained far away, and in Khuzestan province, livestock are facing a shortage of fodder in the winter season. Rapeseed cultivation can be one of the basic solutions to provide the fodder needed by livestock in this season.
Materials and Methods
The research was carried out with the aim of investigating the qualitative characteristics and performance of canola genotypes under the treatment of irrigation interruption and plant density in the agricultural year 2022-2023 at Khuzestan University of Agricultural Sciences and Natural Resources in the form of a split factorial design in the form of a randomized complete block design with three replications. The main factors include (1. control without interruption of irrigation, 2. interruption of irrigation at the beginning of flowering (phenology code 60) to 50% of fruiting (phenology code 75) and interruption of irrigation in the phase of fruiting until harvest (phenology code 71-99)), canola genotypes (Hyola 4815 and Aram) and plant density (80, 110 and 140 plants per square meter) were considered as secondary factors.
Results and Discussion
The results of the analysis of variance showed that the interaction between the treatments of irrigation interruption, and genotype in plant density on the traits of the number of branches, insoluble content in acidic detergent, ash content, total digestible nutrients, digestible dry matter, lactation specific energy and metabolizable energy was significant. The highest amount of total digestible nutrients, amount of metabolizable energy, digestible dry matter and milking specific energy were assigned to Aram genotype and the density of 80 plants per square meter and the treatment of irrigation interruption from seeding to harvest. The highest and lowest content of insoluble fibers in acidic detergent was obtained from the control treatment combination (optimal irrigation), density of 140 plants per square meter and Hyola 4815 genotype, and interruption of irrigation in the third stage, density of 80 plants per square meter and Aram genotype.
Conclusion
The results of this experiment showed that between the experimental treatments in terms of performance of fresh fodder, dry fodder and quantitative and qualitative indicators including morphological traits, insoluble fibers in neutral and acidic detergent, total digestible nutrient, dry matter consumption, specific energy of lactation, there was a significant difference in metabolic energy and relative nutritional energy. The highest yield of dry fodder was observed from the treatment with the density of 140 plants per square meter and the Aram genotype, and the lowest amount was from the Hyola 4815 genotype and the density of 140 plants per square meter. Also, the highest total digestible nutrient, amount of metabolizable energy, digestible dry matter and lactation specific energy were observed according to the Aram genotype and the density of 80 plants per square meter and the conditions of stress from tillering to harvest.