the effect of weed management practices and planting patterns on dry matter accumulation and individual plant growth indicators in peanut cultivars (arachis hypogaea l.)

Introduction: peanuts (arachis hypogaea l.) have significant nutritional value due to their high content of protein (20-25%), oil (45-55%), carbohydrates (16-18%), minerals (5%), fatty acids, and various vitamins. they also hold considerable commercial value (güllüoğlu et al., 2016). peanut cultivars are significantly influenced by soil type and the length of the growing season. given the limited area under peanut cultivation in iran, it is essential to implement various agricultural practices, such as optimizing plant density and planting pattern, to increase yield (koochaki and khalghani, 1997). dry matter allocation is also affected by planting pattern; studies have shown that square planting rows result in maximum dry matter allocation during the podding period compared to the rectangular planting rows commonly used in the region (jaaffar and gardner, 1988). in one experiment, the leaf area index and dry matter production increased with higher plant density (minh et al., 2021). weed control is the most critical production factor in peanut cultivation, with the choice of method depending on both effectiveness and cost-efficiency (mathew et al., 2021). in light of these factors and the importance of planting pattern and weed control in peanut cultivation, this experiment aims to investigate the effects of planting pattern and weed management on dry matter accumulation and one-plant growth indicators in peanut cultivars under the weather conditions of kermanshah. materials and methods: this experiment was conducted as a factorial based on a randomized complete block design with three replications at the research farm of razi university in kermanshah, iran, in 1400. the experimental factors included: (1) peanut cultivars nc2 (north carolina 2) and nc7 (north carolina 7); (2) planting patterns—p1 (row spacing of 50 cm × plant spacing of 25 cm) and p2 (row spacing of 75 cm × plant spacing of 18 cm); and (3) various combined weed control methods, as follows: m1: two rounds of hand weeding along with the application of the herbicides treflan (796 g/ha, active ingredient), bentazon (960 g/ha, active ingredient), and haloxyfop (75 g/ha active ingredient), m2: two rounds of hand weeding with treflan (1233 g/ha, active ingredient), m3: two rounds of hand weeding with haloxyfop and bentazon, m4: complete hand weeding throughout the growing season (every two weeks), and m5: a weed-infested control treatment throughout the growing season. to analyze growth indicators, including total dry matter accumulation (tdm), crop growth rate (cgr), and relative growth rate (rgr), sampling was conducted every 15 days after greening. the pattern of dry matter accumulation was analyzed according to equation 1, the crop growth rate (cgr) was calculated using equation 2, and the relative crop growth rate (rgr) was calculated using equation 3. equation1:tdm =a/(1+〖b.e〗^((-ct) ))) equation2: dy/dt=(a.b.c.e^((-ct) )))/(1+〖b.e〗^((-ct) ) )^2 equation3: rgr=tdm(1/cgr) to calculate and fit the curves related to tdm, cgr, and rgr, sigmaplot v.14 and excel 2016 software were used. results and discussion: at the beginning of the growing season, there was no significant difference in dry matter accumulation between the two planting patterns. however, as the season progressed, dry matter accumulation increased, and by the end of the season, it was higher in p1 than in p2 (figure 1). the allocation of dry matter was also influenced by planting arrangement, with maximum dry matter allocation during the podding period observed in square planting rows compared to the commonly used row patterns in the region (jaaffar and gardner, 1988). an examination of dry matter accumulation in nc2 and nc7 cultivars showed that it increased with the length of the growth period, up to 120 days after emergence. the nc7 cultivar produced more dry matter than nc2 in both planting patterns, with p1 (row spacing of 50 cm × plant spacing of 25 cm) being more effective than p2. this difference was attributed to the nc7 cultivar’s better utilization of space and resources in the p1 patterns, which led to greater dry matter production. additionally, under weed management conditions, nc7 produced more dry matter, demonstrating better competitive ability and higher grain yield (figures 2 and 3). at the beginning of the growth period, changes in crop growth rate (cgr) for both planting patterns were minimal. as the plants grew (around 60 days after emergence), the crop growth rate gradually increased, reaching its peak in planting patterns p1 (row spacing of 50 cm × plant spacing of 25 cm). as the plants aged (about 100 days after emergence), the crop growth rate gradually declined (figure 4). in a related study, it was shown that the square planting patterns of peanuts led to a higher leaf area index than the rectangular patterns during the 45 to 90 days post-planting period. this increase in leaf area improved light distribution, nutrient absorption, and reduced plant competition, resulting in better growth in the square patterns compared to the rectangular one (choudhury, 1997). during the growing season, the highest relative growth rate (rgr) was observed at the beginning of the season, with this rate gradually declining as the plants aged, reaching a minimum at the end of the season. overall, the relative growth rate in the p1 planting patterns was higher than in p2 (figure 5). the decline in rgr coinciding with plant physiological maturity may be due to leaf shedding and shading of lower leaves by upper leaves, which reduces the photosynthetic capacity of the lower leaves (banik et al., 2009). conclusion: the results showed that the p1 planting patterns (row spacing of 50 cm × plant spacing of 25 cm) led to greater dry matter accumulation, crop growth rate, and relative growth rate compared to the p2 patterns. the nc7 cultivar also produced more dry matter and outperformed nc2 in both planting arrangements, particularly under weed management conditions. the main reason for the superiority of the p1 arrangement and the nc7 cultivar in dry matter production and growth rate was the increased efficiency in space and resource utilization within the p1 patterns.