Green light for China’s red soils
No-tillDescription Also known as conservation tillage or zero tillage is a way of growing crops from year to year without disturbing the soil through tillage ie cultivating the soil usually with tractor-drawn implements. Authoritative On-line References and Resources http://www.no-till.com/index.htm A portal for on-line information about no-till farming. crop production using paraquat for weed control is enabling the successful cultivation of one of China’s last available soil resources for food production.
China has 7% of the world’s arable land but has to feed more than 20% of the world’s population. In Southern China red soils account for one fifth of the country's land area where 480 million people live.
At present, nearly 30 million hectares of red soils have been cultivated, but they are highly weathered, inherently infertile and very susceptible to erosion1. No-till can help by stabilizing the soil to resist erosion and by conserving water. The higher levels of organic matter in no-till soils are also crucial to raising soil fertility.
Not tilling the soil means that less organic matter is oxidized, so building-up levels over time. Organic matter is essential for soil health and structure. In the red soils, higher levels of organic matter have an important impact on fertility, especially with regard to nitrogen and phosphorus1. Also, although the third longest river in the world, the Yangtze, flows through the region, lack of water is a major limitation to growing crops. The structure of no-till soils allows much better conservation of water through greater infiltration and less evaporation.
In the mountainous areas upstream of the Yangtze river, perennial crops such as fruit and tea are grown. Erosion of the fragile red soil is a huge problem. Over the past few years research has demonstrated how the successful cultivation of red soils on steep slopes starts with weed control. Trial plots were established in peach orchards and tea plantations to compare traditional farming techniques of hand-weeding and tillage with the use of paraquat and no tillage. A retaining wall was built at the foot of each sloping plot to collect water and soil running off the land. The benefits of using paraquat soon became obvious. For example, water run-offDescription The occurrence of surplus liquid (like rain) which originates up-slope and is collected beyond the ability of the soil to absorb it. The surplus liquid then flows away over the surface to reach the nearest surface water (pond, lake, river). Authoritative On-line References and Resources http://www.sowap.org/index.htm SOWAP (Soil and Water Protection) is a collaboration between industry, NGOs, universities and farmers to test a range of site-specific soil management methods, based on the concept of conservation tillage. It has looked at economic and environment aspects including effects on soil erosion and run-off. from land with a slope of 25 degrees and weeded by hand averaged 427 m3 per hectare per year, whereas when using paraquat it was only 224 m3. Loss of topsoil using traditional farming averaged 2.3 tonnes per hectare compared to only 1.3 tonnes per hectare with paraquat and no-till.
In the lowlands along the Yangtze, typical rotations of arable crops within a single year include wheat or canola (rape) planted in the autumn, then rice harvested in summer, then one or more crops of vegetables. Fields are then fallowed for a few weeks before returning to wheat or canola. Attempting to grow so many crops in the same fields means a rapid changeover is critical. This is where the unprecedented speed of action of paraquat for controlling weeds before planting is really appreciated by farmers. Also, because paraquat is inactivated immediately on contact with the soil, the next crops can be planted very quickly.
No-till rice farming has three key effects:
- On soil : better structure and fertility means better growth of rice roots
- On rice shoots: heavier grains and less straw
- On timing: quicker crop establishment
Rice straw can be laid on the no-till wheat fields after they have been sown. This practice inhibits the emergence of new flushes of weeds in the crop and reduces the need to spray other herbicides.
Using paraquat in no-till farming also saves on labor, cattle (to draw plows), fuel and fertilizer. There is now increased awareness of no-till in agricultural production at all levels of land management, including government.
References
- Wilson MJ, Zhenli He and Xiaoe Yang (2004). The red soils of China. Their nature, management and utilization. Kluwer Academic Publishers: Netherlands.