NO-TILL VEGETABLE PRODUCTION USING ORGANIC MULCHES

Autor: Gordon Rogers, S. J. Silcock, L. F. Williams, S. A. Little
Rok vydání: 2004
Předmět:
Zdroj: Acta Horticulturae. :215-223
ISSN: 2406-6168
0567-7572
DOI: 10.17660/actahortic.2004.638.28
Popis: Conventional tillage practices and the use of polyethylene mulch has led to the loss of soil organic matter and increasing problems of erosion, water logging and soil compaction. A no-till system using permanent beds, permanent sub-surface irrigation and organic mulches grown in-situ, based on that developed by Abdul–Baki & Teasdale (1993) has been implemented as an alternative to conventional production. The system uses a tropical legume, Centrosema pubescens ‘Cavalcade’, or the C4 grasses Bothriochloa pertusa ‘Keppel’ or ‘Hatch’ as cover crops over summer and fall. Cover crops are killed using glyphosate (1440g ai/Ha) and the residues left on the soil surface. Vegetable seedlings are then planted through the mulch residues and grown using conventional agronomic techniques. Following harvest, crop residues are macerated and the following cover crop direct seeded through the mulch residues. The development and implementation of this no-till system of vegetable production has resulted in significant improvements in soil aggregate stability, soil bulk density and soil biological activity, compared to polyethylene mulch and cultivation while crop yields are similar or improved. INTRODUCTION Vegetable crops are commonly grown in soils cultivated for structural management and weed control. Disposable drip irrigation is also often installed and removed annually, and herbicides or polyethylene mulch used to control weeds and protect fruit. While these practices produce high quality crops, they can also lead to a rapid decline in soil physical properties, and a subsequent reduction in crop yields. The yield decline appears to be related to poor soil physical conditions associated with declining organic matter levels combined with an increase in the incidence of soil-borne diseases (Adem and Tisdall, 1984; Morse, 1999). These conventional practices limit further sophistication of the production system and present problems of sustainability in the long term. Cultivation and soil compression can be minimized by the use of permanent beds and controlled traffic (Adem and Tisdall, 1984; Lamers et al., 1986). Without additions of soil organic matter however, a permanent bed system cannot be sustained in the long term. Organic matter can be supplied in such systems by growing cover crops that are subsequently killed and left in place. This technique results in an organic residue on the soil surface that can control weeds and improve soil physical condition (Abdul-Baki et al., 1996; Abdul-Baki et al., 1997; Abdul-Baki and Teasdale, 1993; Teasdale and Abdul-Baki 1995). If the soil is left undisturbed as the cover crop residues decay, the soil space previously occupied by roots become biopores that provide useful voids through which air and water can penetrate (Stirzaker and White, 1995). Organic mulch residues left on the soil surface of uncultivated soil can improve soil moisture retention properties compared to bare cultivated soil (Schonbeck et al., 1993; Creamer et al., 1996 and Saiju et al., 2000). Proc. XXVI IHC – Sustainability of Horticultural Systems Eds. L. Bertschinger and J.D. Anderson Acta Hort. 638, ISHS 2004 Publication supported by Can. Int. Dev. Agency (CIDA) 216 In most crops tested, the improved soil physical and biological properties found the no-till, cover crop system result in delayed but higher yields compared to growing systems involving cultivation. Yield increases have been observed in: tomatoes (AbdulBaki and Teasdale, 1993; Abdul-Baki et al., 1996); lettuce (Stirzaker et al., 1989; Stirzaker et al., 1993); cabbage (Morse and Seward, 1986; Morse, 1993; Schonbeck et al., 1993); broccoli (Morse and Seward, 1986; Schonbeck et al., 1993); and snap beans (De Frank and Putnum, 1978). Equivalent yields to conventional tillage were observed in: broccoli (Abdul-Baki et al., 1997) and cabbage (Morse, 1993). Some studies however (Bottenberg et al., 1999; Roberts et al., 1999) found that crops grown in mulch residues can produce lower yields than conventional production. Work undertaken by Brandenberger & Wiedenfeld (1997) showed that yield, fruit soluble solids and size of muskmelons grown on organic mulches were lower relative to a polyethylene mulch control. Wivutvongvana et al. (1991) also found lower yields under organic mulch and attributed this to a more stable diurnal soil temperature pattern under the polyethylene mulch control. Soils under organic mulches are around 3-5 C cooler than bare soil or under polyethylene mulch (Stirzaker et al. 1989; Schonbeck et al. 1993; Stirzaker and White 1995; Creamer et al. 1996 and Borowry and Jelonkiewicz 2000). The objective of the research was to develop a no-till, cover crop mulch system of vegetable production for the winter vegetable production areas of Australia and investigate the changes in soil bulk density, soil aggregate stability, earthworm populations, and crop yield under the no-till, cover crop mulch regime relative to conventional tillage and crop production under polyethylene mulch. MATERIALS AND METHODS The research was undertaken at trial sites in Bowen, North Queensland as part of a four-year study developing a permanent bed system for fresh-market tomato production using cover crop mulches. The experimental site was established on two neighbouring fields of 1.6ha (no-till system) and 1.0ha (conventional production) respectively with 8 randomly positioned 10m long plots. The entire research site was part of a commercial tomato farming enterprise located at 19° 57’S and 148° 21’E near the town of Bowen, Queensland. Soil at the site was a light sandy clay loam of pH 7.1, 0.7% organic matter and CEC of 6.9 meq.100g. The soil was formed into beds and trickle irrigation tube laid 25 cm below the soil surface. Pre-plant basal fertilizer, which supplied nitrogen, phosphorus and potassium at 50; 50 and 40 kg/ha respectively, was banded and incorporated during the bed forming process. Cover crops of tropical legume Centrosema pubescens or tropical grass Bothriochloa pertusa ‘Keppel’ and ‘Hatch’ as well as Sorghum bicolor were direct seeded at 30, 4, 4, and 30 kg/ha respectively during summer and fall. After 8 to 10 weeks, the cover crops were killed by spraying with glyphosate at 1440 g ai/Ha, and residues left on the soil surface. In late fall, tomato seedlings were transplanted through the mulch residues using a modified water wheel or cup planter. The balance of potassium (40 kg/ha) and nitrogen (25 kg/ha) was applied via fertigation, and crop nutrition checked using leaf analysis and comparing nutrient concentrations to published levels. The tomato crop was then trellised and managed conventionally and weeds growing through the mulch resides controlled using directed herbicide sprays, or hand weeding. Following the tomato crop harvest in spring, crop residues were broken up using a flail mulcher, base fertilisers drilled through remaining surface residues while the new cover crops were sown using a no-till seeder. No separate cultivation step was required once the beds were formed initially. Following the establishment of a permanent bed/organic mulch system on a commercial basis, a study of soil physical characteristics was undertaken to quantify the changes in soil stability and compaction in relation to areas under conventional production. In the comparative conventional system, soil was cultivated using rippers and
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