Compost Use and Weed Management

Tacy CalliesTip of the Week, weeds

Figure 1: Weeds have emerged on a compost pile. (Photo by Robert Riefer, UF/IFAS)

By Ramdas Kanissery

Application of compost as a soil amendment could be an integral part of citrus production’s best management practices. Compost application can potentially improve soil quality and provide additional nourishment to trees. Citrus-producing soils in Florida are generally sandy and low in soil organic matter. Compost addition tends to enhance the soil’s ability to retain both nutrients and water, thereby improving fertilizer-use efficiency.

Compost can be a citrus grower’s best friend. However, if the product used is not formed through a proper composting approach, chances are there will be weed management problems for years to come.

Composting is a decomposition process whereby microorganisms convert raw organic materials like yard trimmings, food wastes, agricultural wastes etc., into a stable product that looks like rich soil. But many of the ingredients in the compost mix can also be potential sources of weed seeds. The proper composting procedure is expected to eliminate viable weed seeds due to heat exposure. However, incorrect composting temperature or lack of periodic turning and mixing the pile during the composting process can result in the survival of weed seeds in the final product (Figure 1). Only use product that is weed-free and comes from a reliable source. Otherwise, it could introduce more weeds to groves.

To check for the presence of weed seeds in compost before its application in the grove, mix several portions of compost taken from various parts of the product pile with potting mix in a 1:1 ratio and spread it in flats or trays. Water the trays twice a week to keep the contents moist and place them in a warm location with decent light, where the temperature is maintained at or above 70° F. Observe any weed seedlings that emerge over the following two to three weeks. This test will generally show if the compost product has viable weed seeds in it.

Keep in mind that effective weed control does not end with the use of properly prepared and weed-free compost products. Citrus benefits from the compost, but so do the weeds. The compost’s nutrients that provide the boost to the citrus trees will also boost the weeds and their seed bank in the soil. It is crucial to ensure that ongoing weed management programs are continued on the citrus groves’ composted areas.

Never apply the compost until all the existing weeds are effectively managed. Adding the compost in weedy tree rows will not suppress existing weeds. Instead, they will grow through the compost. Bear in mind that weeds will eventually start to emerge from the soil in the composted area. Control them when they are young and before they go to seed to prevent future infestation.

Get more information on effectively managing weeds in citrus.

Ramdas Kanissery is an assistant professor at the University of Florida Institute of Food and Agricultural Sciences Southwest Florida Research and Education Center in Immokalee.