Row weeding

Melander, B. 1998b. Interactions between soil cultivation in darkness, flaming and brush weeding when used for in-row weed control in vegetables. Biological Agriculture and Horticulture 16(1) 1-14. 

Paraquat is used for stubble cleaning, presowing and preemergence weed control, inter-row weed control of ploughed land, as a spray for subfoliar weed-control in maize, for inter-row weed-control in orchards, vineyards and tree nurseries, for pasture renovation and for total weed-control in non-crop areas. The rate of application is 0.4-1.5 kg active ingredient/ha. 

Fig. 17.4 Inter-row weeding cabbages (Garford Farm Machinery Ltd).

Some crops can be chosen in organic rotations that control weeds through shading, such as winter wheat, if attention is paid to row... 

The monetary loss due to weeds competing with the first seven row crops listed in Table I was approximately five billion dollars annually. Losses in soybeans [Glycine max (L.)... 

The value of all herbicides for crops marketed worldwide in 1980 was estimated at about 4.9 billion (17). The sale of herbicides for weed control in corn in the United States represented 70 and 49% of the world herbicide and pesticide purchases in corn, respectively. The sale of herbicides in soybeans represents 82 and 69% of the world herbicide and pesticide purchases in soybeans, respectively. The sale of herbicides for weed control in row crops in the United States represents 62 and 36% of the world herbicide and pesticide purchases for row crops, respectively. 

An annual estimated cost of approximately 938,835,000 is required for labor and equipment to apply 204.5 million kilograms of herbicides to 147.6 million hectares of cropland in the United States (Table IV). Mechanical tillage to control weeds between cropping seasons and interrow tillage of crops has been used for centuries as a very effective method of weed control. Approximately 50% of all tillage between crops is done to control weeds. The number of cultivations required for effective weed control within a row crop varies from two to five during a cropping season. 

Tillage for weed control in intertilled row crops cost on the average about 29.65/ha/yr. With approximately 76.9 million ha of intertilled row crops the cost of tillage is in excess of 2.28 billion annually. In drill row crops where tillage is less intent, a cost of about 12.35/ha/yr is required on approximately 70.8 million hectares. The cost in these moderate tilled areas is in excess of 874 million annually. 

Table I. Weeds With Reported Allelopathic Activity Found in Row Crops in the Southern United States...

No tillage or zero tillage the soil is left undisturbed from harvest to planting except for nutrient injection. Planting or drilling is accomplished in a narrow seedbed or slot created by coulters, row cleaners, disk openers, in-row chisels. Weed control is accomplished primarily with herbicides. Cultivation may be used for emergency weed control... 

An example, when intercropping suppressed the weed growth more than sole, is a leek (Allium ampeloprasum var. porrum (L.) J.Gay) - celery (Apium graveo-lens L.) intercrop sown in a row-by-row layout decreased relative soil cover of weeds by 41%, reduced the density and biomass of groundsel (Senecio vulgaris L.) by 58% and 98%, respectively, and increased the total crop yield by 10% (Baumann et al. 2000). Increased weed suppression and the crop yield were also demonstrated in cereal-legume intercrops in many different environments (Ofori et al. 1987). 

Rasmussen IA (2004) The effect of sowing date, stale seedbed, row width and mechanical control on weeds and yields of organic winter wheat. Weed Res 44 12-20 Reddy KC (2001) Effects of cereal and legume cover crop residues on weeds yield, and net return in soybean (Glycine max),. Weed Tech 15 660-668 Reynolds LB, Potter JW, Ball-Coelho BR (2000) Crop rotation with Tagetes sp. is an alternative to chemical fumigation for control of root-lesion nematodes. Agron J 92 957-966 Rice EL (1984) Allelopathy. Academic, New York, p 317... 

Figure 2—Sugar cane about 6 weeks old which has had one spray of 2,4-D amine and 2 sprays of 6CA-4. Weed control is excellent both in irrigation ditches and within rows...

This application was made between 0700 and 0830 a.m. in cool (air temp., 10 0 clear and windless weather. Both granular and emulsion formulations were incorporated to the 7.5cm depth with a disc cultivator within 15 minutes of application. A second cultivation to the same depth, but at right angles to the first, was completed within 2-3 hours. On May 20th both plots were spring-tooth harrowed for seed-bed preparation for soybean planting on the same day. The only subsequent soil disturbance was a row cultivation in late June to control a severe infestation of quack-grass control of broadleaf weeds was essentially complete with the trifluralin. 

When sowing and planting vegetables, remember to leave sufficient space between rows to allow for easy hoeing, unless you are growing in beds using close spacing to smother weeds. 

Growing vegetables in narrow beds, divided by access paths, has many advantages over traditional row cropping. On a traditional vegetable plot, soil improvers and fertilizers are applied across the whole area, and then dug in. The soil between the rows is compacted as crops are watered, fed, weeded, and harvested. A bed system breaks with this constant cycle of compaction followed by cultivation. 

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