Winter 1995 (v7n1)
Aref A. Abdul-Baki and John R. Teasdale
HortScience 28(2):106-108. 1993
This article describes a no-tillage vegetable production system that uses winter annual legumes as both cover crop and plant mulch. According to the authors, this production system is adapted to both large- and small-scale operations. It takes advantage of the benefits that legumes offer, and avoids the difficulties of spreading a mulch uniformly over a field.
The experiment was conducted at the Beltsville, Maryland Research Center. The researchers looked at the effects of the no-tillage system on yield and earliness of fresh market 'Sunny' tomato. Tomatoes following cover crops of hairy vetch and 'Mt. Barker' subterranean clover were compared to those grown under conventional tillage using black polyethylene mulch, Horto paper mulch, and no mulch.
In the cover crop treatments, beds were prepared immediately before sowing of the cover crops. Clover seed was planted on September 5 at a rate of 28 kg per ha; vetch seed was planted on September 18 at a rate of 53 kg per ha. The cover crops were not irrigated and were grown without any other treatment until they were mowed the following spring. In early May, after determinations were made of cover crop growth, the clover and vetch plots were mowed to about 4 cm above the soil surface using a high-speed flail mower. This operation chopped the plants and spread them uniformly over the beds. Five-week-old tomato seedlings were planted through the mulch layer on May 1 (early planting date) and May 8 (optimum planting date). A 7-cm hole was cut through the mulch using a tree planter and then tomatoes were transplanted by hand causing minimal disturbance to the mulch. Trickle irrigation lines were laid over the cut mulch surface 10 cm away from the plants and fixed in position with U- shaped wires. Tomatoes were planted in the comparative systems on the same two dates (May 1 and 8).
The poly mulch, paper mulch and bare soil treatments were irrigated weekly through the drip lines with a 9-6.6-24.9 NPK solution. Cover crop/mulch treatments were fertilized every other week using the same solution. Weeds were controlled as needed in all treatments using herbicides.
| Table 1. Effect of mulch on total and early yield of 'Sunny' fresh-market tomato in the field at early and optimum planting dates. | ||||
| Yield (tons per ha) | ||||
| Treatment | Planting Date | Total | Early a/ | |
| No mulch (control) | Early | 55.0 | 9.71 | |
| Optimum | 51.8 | 6.65 | ||
| Hairy Vetch | Early | 121.1 | 9.49 | |
| Optimum | 137.2 | 5.36 | ||
| Subterranean Clover | Early | 85.7 | 1.93 | |
| Optimum | 95.7 | 1.41 | ||
| Horto paper | Early | 97.7 | 4.54 | |
| Optimum | 95.7 | 6.12 | ||
| Black polyethylene | Early | 99.9 | 16.9 | |
| Optimum | 114.8 | 23.63 | ||
| LSD(0.05) | 12.5 | 3.41 | ||
| a/First four harvest at 5-day intervals | ||||
The effect of the various treatments on tomato yield is shown in table 1. Total tomato yield in the hairy vetch mulch was more than double the yield of the control (nonmulched) plants, and significantly higher for both planting dates than yield from the black polyethylene-mulched plants. The authors attributed the success of the vetch over the clover treatment to its superior winter hardiness in the Beltsville area. "The clover stand was killed on top of beds in winter but produced 3.6 tons per ha of dry matter in the troughs between rows. In contrast, the hairy vetch stand was well established on the beds, and the plants were about I meter long at mowing time, with 3.8 tons per ha above ground dry matter."
In terms of earliness, black polyethylene mulch was superior to all other mulches in enhancing yield. The effects of black polyethylene mulch in warming soil and promoting plant growth have been well-established.
The authors suggest that the vetch mulch offers a number of benefits in this production system. First, mowing and spreading the cover crop provides a thick layer of mulch that reduces soil erosion and soil water evaporation, and that moderates soil temperature. The mulch also eliminates early weed competition (later weed emergence or cover crop regrowth can be controlled with postemergence herbicides.) The authors also conclude that the cover crop residue on the soil surface sustains nitrogen decomposition and release over a longer period than if the cover crop were plowed in.
Reviewer's Comments
The authors have produced a pamphlet for growers that describes this production system in more detail. The title is Sustainable Production of Fresh-Market Tomatoes with Organic Mulches, published by the United States Department of Agriculture, 1994, Farmers' Bulletin FB-2279. Contact Abdul-Baki for information about how to order the pamphlet (see address below).
Adapting the no-till mulch production system to California conditions will require careful management on the part of growers. Major considerations include: 1) the choice of cover crop; 2) the effect of the mulch on soil insect pests; 3) the tendency of the mulch to keep the soil cool in the spring; 4) the time of mowing as it relates to conservation of soil water; and 5) the relative costs and benefits of other types 'of mulches.
For more information write to: A. Abdul-Baki, USDA-ARS, Vegetable Laboratory, Building 4, BARC- West, Beltsville, MD 20705.
(DEC.523)
Contributed by David Chaney
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