Profitable no-till cropping requires excellent crop agronomy. This is because 'tillage covers a multiple of sins'. Tillage has been used for thousands of years to kill pests, particularly weeds, reduce diseases and soften the soil for fast root growth and nutrient release. When adopting less tillage we need to manage these factors by other means. Rotation of crops is the principal tool that must be used for effective no-tilling.
Some of the benefits of no-till, like improved water harvesting, are seen immediately while others are only realised in the long term. The progression of the no-till system over time has been divided into four phases in Figure 1 (Sá, 2004). In the initial phase (0 to 5 years) the rebuilding of soil aggregates begins and measurable changes in the organic carbon content of the soil are not expected. There are low crop residues and nitrogen needs to be added to the system.
The next 5 years (5 to 10 years) are the transition phase where there is an increase in soil density, soil carbon, phosphorus and the amount of crop residues on the soil surface. In the consolidation phase (10 to 20 years) greater amounts of crop residue and soil carbon are achieved. The soil water holding capacity and cation exchange capacity are increased and greater nutrient cycling is observed.
It is only in the maintenance phase (>20 years) that the ideal situation with the maximum benefits for the soil is achieved and less fertiliser is required (Derpsch, 2005).
Figure 1. Progression of the no-tillage system over time
(derived from Sá, 2004)
References:
Derpsch, R.W. (2005). Situational Analysis of No-Tillage Systems in WA and Recommendations for the Way Forward. A Report on a Consultancy to WANTFA, GRDC and DAFF.
Sá, J.C. M., 2004: Adubação Fosfatada no Sistema de Plantio Direto. In: Sympósio sobre Fósforo na Agricultura Brasileira, Anais (ed.) T. Yamada, Silvia, R. S. Abdalla, p.201-222, Piracicaba, SP, POTAFÓS, 2004, 726p.
One of the main challenges to no-till cropping is the increased use of herbicides for weed control, because cultivation is rarely used. Continued use of a narrow range of herbicides can result in the selection of weeds that are resistant to the specific chemicals. It is important to consider an integrated approach to weed management and one of the key priorities is to diversify the rotations so that different chemicals, times of sowing and crop competitiveness can be utilised.
Published 12 November 2009 Reviewed 23 December 2009
