Ground cover during fallow from wheat, sorghum and sunflower stubble under three tillage practices in Central Queensland

• Published in: Soil & tillage research Vol. 12; no. 4; pp. 347 - 364
• Main Authors: Sallaway, M.M., Lawson, D., Yule, D.F.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 1988; Elsevier
• Subjects: Agronomy. Soil science and plant productions; Biological and medical sciences; BLE; CROP RESIDUES; Cropping systems. Cultivation. Soil tillage; Fundamental and applied biological sciences. Psychology; General agronomy. Plant production; HELIANTHUS ANNUUS; LABRANZA; QUEENSLAND; RESIDU DE RECOLTE; RESIDUOS DE COSECHAS; SORGHUM; TILLAGE; Tillage. Tending. Growth control; TRAVAIL DU SOL; TRIGO; WHEATS; Cultural practice; Monocotyledones; Soil erosion; Soil tillage; Zero tillage; Compositae; Cereal crop; Oil plant(vegetal); Oceania; Soil conservation; Plowing; Sorghum bicolor; Helianthus annuus; Gramineae; Dicotyledones; Angiospermae; Spermatophyta; Mulching; Australia; Triticum aestivum; Fallow
• ISSN: 0167-1987; 1879-3444
• DOI: 10.1016/0167-1987(88)90045-1

As part of a large scale study into the effect of soil-surface conditions and crop residues on runoff and soil loss, techniques to estimate cover were developed. The vertical projection of cover was measured from photographs of 9 treatments (3 crop species × 3 tillage practices), while stubble weight was estimated using a calibrated visual-rating technique. The techniques were then used to quantify the stubble resulting from different crops, grain yields, tillages and over time. Projected cover post-harvest is a function of crop species and seasonal effects as expressed in grain yield, and was in the order wheat (90.3), sorghum (58.5) and sunflower (43.1). Projected cover was linearly related to grain yield. During the fallow, tillage had a large effect on decreasing projected cover, with change in projected cover during the fallow being in the order: zero tillage<blade/chisel<disc/chisel, and implement effects ranging from 65% reduction (disc), 19% reduction (blade plough) to 12% reduction for secondary cultivation by chisel plough or scarifier. Use of a projected cover ratio coalesced crop data across years so that a constant decay rate could be applied to all crops. Projected cover and stubble weight were related in the form: Projected Cover=m[1−e −stubble weight], with the asymptote value, m, varying for each crop and ranging from 98.1 for wheat and 64.7 for sorghum to 49.3 for sunflowers. From the relationships of projected cover to grain yield or stubble weight and a knowledge of how it changes over time or owing to cultivation, a predictive equation was developed to determine projected cover at any stage in the fallow.