Maize emergence under conservation agriculture

CEDRIC BALOYI, ARC-GRAIN CROPS INSTITUTE

Many people in South Africa face a huge challenge of alleviating starvation and poverty and mainly depend on subsistence/small -holder rainfed farming for their livelihoods. It will therefore be required to double agricultural yields over the forthcoming decades in order to meet this challenge.
 
Another challenge would be to change the poor soil fertility status due to intensive practices such as deep ploughing (conventional tillage) and planting the same crop year after year (monoculture) and burning of crop residues that leave the soil unprotected to wind and water erosion.

Conservation agricultural systems such as minimal soil disturbance (minimum tillage), soil cover and crop rotation have been used as an alternative to conventional tillage practices in order to reduce production costs and increase especially soil “health” conditions. These technologies are thought to be a solution for the problems of poor agricultural yields and soil nutrition under South African condition.

Conservation agriculture could lead among other things, to reduction in costs of fuel, labour and tractors and the ability to use land at lower risk of erosion for more intensive crop production. In South Africa there has been a low adoption of conservation agriculture among producers.

The use of heavier farm machinery during ploughing lead to an increase in soil strength and bulk density, and causes soil compaction which often restricts growth of plant roots, particularly at low moisture levels. Planting of crops either in a no-till or reduced till system has problems related to the forming of natural compaction, which is common when planting the same crop year after year.

The situation could even worsen under small-holder farming activities where recommended plant density depends on the quantity of seed obtained due to cost. As part of the ARC-Grain Crops Institute (ARC-GCI) conservation agriculture projects group, this study was initiated to assess maize emergence at different plant densities under two tillage practices and two row widths.

Evaluation information and procedure

Three on-farm rainfed field trials were conducted at Boskop, Poortjie and Ventersdorp during 2011/2012 using four maize (PAN 6Q433B) plant densities (10 000, 20 000, 30 000 and 40 000 plants per hectare). These plant densities (Graph 1) were evaluated under two tillage practices (minimum and deep ploughing) and two row widths (0,9 m and 1,5 m).

Each plot comprised of four rows, each 10 m long. All the localities had a very low content of NPK, except for the adequate K content (250 mg K kg) at Boskop. All plots received the same amount of fertiliser in the form of NPK. All the other agronomic practices werekept uniform during the cropping season. The soil at Boskop was sandy clay loam and sandy loam at Poortjie and Ventersdorp, respectively. Rainfall during the planting season ranged from 300 mm to 450 mm across the localities. Percentage maize seedling emergence (PE) and the mean emergence dates (MED) were calculated from the first to the last day of emergence in 7 m of the two middle rows.

Results

Planting maize at lower density (10 000 and 20 000 plants per hectare) in either 0,9 m or 1,5 m, will result in lower mean emergence dates (MED) of maize whether planted in clay or sandy soil. However, when planting at higher plant density, producers should plant in 0,9 m spacing in order to shorten the emergence of plants per day, since wider rows (1,5 m) will cause a delay.

Moreover, planting higher densities (30 000 and 40 000 plants per hectare) in narrower rows (0,9 m) in clayey soil will shorten the mean daily maize emergence (MED), but will be delayed in sandy soil due to poor seed/soil contact.

Choosing tillage practice, producers can either plough using minimum (minimum soil disturbance) or deep (conventional) tillage. Both tillage practices will result in the same percentage emergence of maize seedlings and mean emergence of maize seedlings per day. Again, planting maize seedlings either in narrower (0,9 m) or wider rows (1,5 m) will result in the same percentage of emerged plants. However, maize emergence per day (MED) will be in a shorter period when maize is planted in narrower rows
(0,9 m).

Selecting plant density

Maize seedling will emerge better at low plant density (10 000 plants per hectare) probably due to the lack of competition between plants. Planting a higher density of maize is commonly linked with increased maize yield in a hectare. However, the percentage of maize emergence at higher density (40 000 plants per hectare) will be reduced due to competition of plants for moisture, nutrients and sunlight (Graph 2a and b). Planting lower maize densities (10 000 and 20 000 plants per hectare) will reduce the daily mean emergence of maize. The shorter daily emergence of maize plants will enable crops to mature and be harvested at the same time.

Producers can plant maize in either sandy or clay (less than 35%) soil since these soil types in the different localities used will result in the same percentage amount of maize emergence. Daily mean emergence of plants will be in a shorter period in clay soil probably due to the better seed/soil contact than in sandy soil (Graph 3).

For more information on maize emergence under conservation agriculture, contact Cedric Baloyi at (018) 299-6100.