Effect of seed pre-treatment with biological and chemical agents and herbicide application on growth and yield of dry bean (Phaseolus vulgaris L.) landrace

Among three market class of bean (Phaseolus vulgaris L.) landrace in Guilan province, black streaked (Ojo de Cabra) has the highest cultivated area. This type of bean is a determinate bush with purple flowers, kidney-shaped seeds coated with black streaks in creamy background and hundred seed weight of 37 g. The great yield loss of bean posed by weeds represents the importance of planning effective weed control programs. With respect to increasing environmental concerns, if crop suppressive ability could be integrated into a weed management strategy, then the potential for improved weed control and reduced herbicide inputs would be promising. Every agronomic practices aim to improve germination extent, evenness and rate, seedling emergence and establishment, and plant growth and development for crop rather than weeds, would lead to enhance competitiveness of crop against weeds. Seed priming is a physiological technique in which seed hydration and drying occurs. Conventional methods of seed priming are hydro-priming, bio-priming, chemical priming, osmo-priming, nutrient priming, and priming with plant growth regulators. Seed priming due to promoting germination, emergence, and early growth of crop can ensure vigorous plants which may strongly compete with weeds. Therefore, priming could be expected to confer a competitive advantage on the crop. In this experiment, the possibility of utilizing priming in order to reduce the applied dose of two common bean herbicides, trifluralin and bentazone, were investigated.

order to study the effect of seed pre-treatment with biological and chemical agents and herbicide application on growth and yield of dry bean landrace of black streaked (market class of Ojo de Cabra) as a common and widely used landrace in Guilan province, this field study was conducted at the University of Guilan in 2015. Treatments were arranged as a factorial with four seed pre-treatments and five weed management programs for a total of 20 treatments in a randomized complete block design with three replications. Seed pre-treatment consisted of priming by zinc sulphate and by salicylic acid, biopriming by Pseudomonas bacteria, and without priming. Weed management program included weed free (hand weeding), and weed infested condition, and 100, 75 and 50% recommended dose of trifluralin (Treflan, EC 48%, recommended dose of 960 g ai. ha-1) and bentazon (Basagran, SL 48%, recommended dose of 960 g ai. ha-1). To study the growth and development of bean, five stages of samples were taken. first destructive samplings were done at 16 days after planting and repeated every 14 days up to the last sampling was done at 72 days after planting (samples were taken 16, 30, 44, 58 and 72 days after planting). At each sampling, plant height, Leaf area and dry weight, and stem and total dry weight of bean plants were measured. Number and weight of pods, and biological yield were also determined at the last (5th) sampling time. Data were subjected to ANOVA, using SAS v. 9.2. Means were separated using Fisher’s Protected LSD test at the 0.05 level of significance.

The height of bean plants was higher by 11% in priming by salicylic acid compared to non-priming treatments. Seed biopriming by Pseudomonas bacteria compared to non-priming treatment increased the maximum leaf area index, maximum leaf dry weight, total dry weight, number of pods per square meter, and biological yield by 30, 69, 50, 31, and 50%, respectively. Weed management also affected crop production. The highest amounts of the measured traits were recorded for treatments of weed free condition and recommended dose of herbicides. The values of measured traits reduced as herbicide dose decreased. Full-season weed infested condition compared to weed free condition reduced the maximum leaf area index, maximum leaf dry weight, total dry weight, number and weight of pods per square meter, and biological yield by 40, 58, 58, 72, 70, and 58%, respectively. The lowest values belonged to weed infested condition. The effect of reduced rate application of 75% of the recommended dose of trifluralin and bentazon were not significantly different from recommended dose of two herbicides for all traits in all sampling times, except the stem dry weight in third sampling, and pod numbers per square meter. Therefor it seems possible to apply reduced dose of recommended herbicides while minimizing weed competitive effects and maintaining economic returns of bean production. This also would decline undesirable effects accompanied by herbicide application including herbicide-resistant weed populations that challenge sustainability of weed management programs.

However, non-significant interaction of seed pre-treatment and herbicide application revealed that despite seed priming methods was positively correlated with growth, development and production of bean, but not with competitiveness of the crop, and thus could not provide a reliable management strategy to reduced herbicide inputs. Generally, since implementation of integrated weed management systems are of fundamental importance in modern weed control, more attention should be given to the possibility of setting up weed control programs involving herbicides reduced dose application combined with crop competitive ability.