Integrating Mechanical and Chemical Methods for Weed Control in the Potato Fields

The presence of weeds seriously reduces potato yield by particularly where crop competition is reduced because of poor growing conditions or disease or in cultivars where development rate is slow. Weeds can also have a serious effect on harvesting the crop, entangling equipment and slowing operations. They can also encourage some pests and diseases such as slugs, free living nematodes, wireworm and Rhizoctonia. The potato crop, once the haulm meets in the rows, is usually effective in reducing late weed emergence through shading. However, weeds emerging before row closure can grow above the crop canopy. Noxious weeds such as field bindweed and knotgrass can grow through the crop, and tall weeds, such as fat-hen, sow thistles, and grasses, can grow above the crop, shading and competing strongly for resources. Weed control needs to start whilst the weeds are accessible to treatment, that is, pre-emergence of the crop to before the crop shades emerged weeds. The treatment needs to be able to maintain weed control for up to 6-8 weeks after crop emergence to allow the crop canopy to close and shade further weed emergence. In less vigorous and less competitive varieties, canopy closure may take longer, or remain incomplete. In conventional farming systems, treatments are based on herbicide treatment. This may be before weeds and crop emergence with a residual soil-acting herbicide which gives a number of weeks of control, depending on dose, soil type and weather conditions. Some residual herbicides have some foliar as well as root activity and can be used as the weeds and crop emerge. Mixtures with a contact herbicide are often used at this timing. This timing, slightly later than purely pre-emergence of the crop, allows the residual effect of soil-acting herbicides to persist for longer into the season. This is particularly useful for slow growing varieties or in slow growing conditions. The objective of this study was to evaluate the effect of integrated weed management, using chemical and mechanical methods, on weed density and biomass of potato C.V. Agria. 

To evaluate the effect of cultivator and herbicide application on yield and weed community of potato, an experiment was conducted using factorial arrangement based on randomized complete block design with four replications at the Research Field of Ferdowsi University of Mashhad in 2015. Factors included cultivator at two levels (no and once cultivator) and herbicide application at six levels (pre-planting application of pendimethalin+broadcast application of metribuzine as post-emergence, pre-planting application of pendimethalin+band application of metribuzine as post-emergence, pre-planting application of pendimethalin alone, broadcast application of metribuzine as post-emergence alone, band application of metribuzine post-emergence  alone, and no herbicide treatment). In addition to these treatments, a weed free treatment as a control considered in each block. Weed flora, total weed density and total weed biomass recorded at 15, 30, 45 and 90 days after treatment using a 0.35×0.75 m-2 quadrates. At the harvest time, tuber yield and potato biomass recorded in 2 m2 area. Data analysis; including ANOVA and mean differences at the 5 %significant level was done using SAS 9.1 and figures created using Excel 2007.

The results showed that cultivator just had significant effect on total weed density and had no significant effect on total weed biomass and potato yield. Application of pendimethalin+metribuzine using broadcast or band application method reduced total weeds density and total weed biomass and increased tuber yield, and biomass of potato. The lowest weed biomass (250.2 and 212.2 g.m-2) and highest tuber yield observed in application pendimethalin+metribuzine broadcast and band application  method, 41.158 and 36.168 ton.ha-1 ,respectively and highest weed biomass (900.1 and 933.9 g.m-2) and lowest tuber's yield observed in no herbicides and pendimethalin alone, 16.482 and 18.752 ton.ha-1 , respectively.

It was concluded that one cultivator alone not only could not help to weed control program, but also excite weed emergence. Then repeating the cultivator operation or application of pre-planting or post-emergence herbicide is necessary to achieve a good weed control in potato. In addition, integration band application of post emergence metribuzine and cultivation between rows reduced significantly herbicide application in potato.