Planting

Since the costs of replanting a sugarcane field are far higher than those of re-establishing a field after harvest, it makes good sense to do everything possible to ensure a good and healthy plant crop. The requirements for a good and healthy plant crop are favorable soil and moisture conditions as well as healthy seedcane of the right cultivar. Factors such as depth of planting, depth of covering and timing all play a role. Of critical significance is the fact that 85-90 % of erosion on a sugarcane farm occurs during crop re-establishment (Platford 1987). Mechanical planting has been adopted in many mechanized industries, but hand planting is still widely practiced.

Soil testing and amendments application (liming)

Soil sampling and analysis should be carried out immediately after harvesting to enable the formulation of plans to apply the required fertilizers, and importantly to identify the need for any ameliorative treatments such as lime. The simple exercise of applying fertilizers according to soil analysis and industry calibrated recommendations avoids excesses and saves costs, thus contributing to both economic and environmental sustainability. Where a legume fallow has been used it should also be remembered that that the N recommendation at planting and in the first ratoon crop will need to be reduced. This could be regarded as one of the simplest and most effective ways of helping the achievement of economic and environmental sustainability (See Chapter 5).

Timing of planting

For irrigated areas temperature is not generally the limiting factor in timing of planting, whereas under rainfed conditions usually only a restricted time or season is available for planting. Diseases may be more prevalent at certain times of the year (mosaic is a problem in some areas planted after November in South Africa). Spring is the most common time of planting and this requires that the previous crop should have been eradicated in winter. It is important to ensure that time of planting is geared to minimize potential soil erosion by planting fields on steep slopes and with erodible soils when these would be least affected by heavy rain events. In areas having some winter rainfall, winter planting can be accomplished by applications of 3-4 L/m of water to the planting furrow.

Although autumn planting allows the crop to be at full canopy early in the spring and enables best use of summer growing conditions, the previous crop would have been in fallow during the peak growing season.

Cultivar selection and seedcane production

Cultivars differ in a range of important characteristics and play a critical part in the economic success of a farming operation. Most industries have substantial breeding and evaluation programs for cultivars and make recommendations based on disease resistance, pest resistance, and yielding ability under the range of climate and soil type situations in their industries (see Chapter 2.4).

Diseases can have a major impact on yield and an effective means of preventing disease is to plant disease free seedcane. Some industries (e.g. Swaziland) manage a seedcane scheme to provide a source of disease free seed of the registered cultivars to all its growers. Some milling companies also provide seed for their growers and in so doing ensure the planting of the most suitable cultivars (see Chapter 8).

The planting furrow

The ideal depth of planting appears to be about 100 mm where soil temperature remains warm and allows for quick germination and emergence. Under hot conditions and in sandy soils it may be warranted to plant slightly deeper. A deep ridge and furrow leaves an uneven soil surface which is not ideal for herbicide application. With hand planting under rainfed conditions better germination is obtained if the time between opening the furrow and covering the planted seed is minimized to take advantage of soil moisture. Fertilizer placed in the furrow should be covered lightly before placing setts in the furrow, to prevent direct contact with the buds.

Seedcane preparation

Seedcane consists of stalks harvested from a nursery, and usually they would be cut at a younger than normal harvest age to ensure that the buds and stalks are all young and healthy. Buds below the top do not germinate unless the top of the stalk is removed or the stalk is chopped into sections.

This is due to an effect of growth inhibiting auxins produced in the top of the stalk. With hand planting, stalks are generally placed whole into the planting furrow and then chopped manually into sections of about 400 mm, or the stalks have the trash removed and are then chopped into setts and dipped in a fungicide where necessary. For autumn or winter planting where germination may be slow, it is advisable to dip setts in a fungicide to prevent pineapple disease. It is important also to ensure that knives are dipped regularly in a disinfectant when chopping stalks, since RSD could be transmitted.

A seedcane rate of at least 8 t/ha should be used to provide a good stand. This usually results in an overlap of 30-50 %. It does not pay to skimp on seedcane (see Chapter 8).

Row spacing (and planting configuration)

To obtain maximum benefit from radiation a full canopy is required and hence any practice which increases the rate to 100 % canopy will be of benefit. Experiments in South Africa have shown that where moisture stress is not too severe, sugarcane yield increases as distance between the rows decreases within certain limits (Boyce 1968). There was a 3 % increase in yield for every 300 mm decrease in row spacing from 2.0 m to 600 mm. In practice a row spacing of 1 m is as close as most field equipment will conveniently allow. Much of the world’s sugarcane has been planted at 1.5 m spacing.

For practical reasons, a standard spacing should be used on all fields on the farm, and there are costs associated with narrower spacings. More seedcane is required, planting takes longer and many farm operations, notably irrigation, take longer and are thus more expensive. A number of factors affect the choice of row spacing and narrower row spacings are an advantage where growth is slow in cooler areas and where cane is grown on slopes or erodible soils.

Tramline row spacing has a number of advantages which may suit mechanized industries. The main benefit is that infield equipment is able to straddle the dual rows and thus prevent damage to the

rows themselves and minimize soil compaction. Mechanical harvesters are able to cut two rows per pass, and trailers for chopper harvesters are also able to avoid running on the cane rows.

Dual rows are used in Australia in their ‘New Farming System’ where legume crops are grown in the fallow. In this system controlled traffic is used in combination with a 1.85 m dual row, minimum tillage, legume breaks and a green cane trash blanket system. A wider row spacing of 1.85 m is required to alleviate the problems of compaction and stool damage caused by infield machinery on the standard 1.5 m rows spacing. Reservations were expressed about the possible loss in yield due to wider row spacing and a number of experiments were established by Garside and Bell (2009a,b) and Garside et al. (2009). It should be noted that the dual rows tend to grow into one wide row after two or more rations.

Figure 3.4. Tramline planting on a large sugar estate in Mpumalanga, South Africa.

The envisaged disadvantages to wider row spacings were not found to exist under good soil health conditions (fumigation), and further experiments demonstrated the ability of sugarcane to

compensate for the lower stalk populations in wider spacings with heavier stalk weights. Although cultivars did differ in their response to wider row spacings, satisfactory yields could be obtained at wider row spacings by choice of the correct cultivar (Garside and Bell 2009b).Other reported benefits of this integrated system of crop establishment are savings in nitrogen fertilizer from using the legume breaks, even into the first and sometimes the second ratoon, better weed control and a marked improvement in soil health in terms of improved organic matter content and soil microbe diversity.

Box 3.10 Examples of the benefits obtained at Loeskow Farm with the new ‘Integrated Farming System’ at Bundaberg, Queensland, Australia (Garside, 2011, personal

communication)

 Total farm size is 1 500 ha.

 943 ha under cane and 134 ha under peanuts.

 Very poor sandy Arenosol soil.

 Has been farming new system since mid-1990s.

 Average cane yield has increased from 53 to 96 tc/ha.

In Argentina, yield responses and major cost savings between cycles from adopting these integrated farming systems were verified in trials conducted on an estate (J Meyer, Durban 2011, personal communication). The advantage is that only the interrows need to be maintained and that at the time of replanting, only the row area (zonal tillage) needs to be cultivated instead of the whole field.

Other reported benefits include N savings in fertilizer use, much better weed control with the trash blanket and minimum tillage, and that many of the sett diseases appear to be better controlled following a legume break. In Swaziland some estates are using GPS tracks for the laying of drip irrigation lines in a dual row planting system. This allows land preparation equipment to avoid damage to the drip lines when eradicating the crop and creating a tilth for the next planting. On estates where standard row widths are still being maintained there is increasing use of GPS controlled steering of infield tractors, mechanized planters and harvesters to minimize stool damage.

Depth of covering

A depth of between 30 and 50 mm is sufficient, as long as this is uniform. Deep covering delays germination. Light consolidation of the soil over the row improves soil sett contact but too heavy a compaction, particularly in wet soils, is not conducive to good germination. Fine sandy loam soils are particularly sensitive to compaction.

Hand and Mechanical Planting

The basic planting requirements of placing cane stalks at the correct depth, at the correct density and overlap as well as ensuring adequate covering and suitable compaction can all be provided by mechanical or hand operations. The choice of system would depend on a number of factors including labor availability and slope as well as the need for dipping seed cane. Numerous studies have been conducted on seed cane preparation to assess the benefits of removing trash, chopping stalks into different lengths, depth of placement and rate of seed cane and in general most requirements can be satisfied by either mechanical planters (possibly with some adaptations) or hand labor. Small farms size lends itself to hand planting but labor shortages are resulting in the use of small mechanical planters even here.

Figure 3.5. Example of a mechanical planter used for small scale farming operations.

Productivity of manual versus mechanized planting

At TSB in Mpumalanga, an average of 57 labor units and six tractor trailers are used to plant 8 ha/day when establishing tramline planting. With 1.5 m single row spacing, 10 ha can be

established with the same resources. This is compared with an average productivity of 160 ha/day with a dual row mechanical planter that is used at San Martinho Estate in Brazil.

Some relatively new systems of planting

Techniques of rapid propagation are being developed for multiplication of new cultivars or to obtain disease free planting material.

Seedlings

Various industries have developed and tested methods of establishing cane from single eyed setts or stalk chips which include a bud, planting these into seedling trays usually in a medium enriched with appropriate fertilizers and then allowing these to become established plantlets. Trays of seedlings are then transported to the field for planting. A planting hole is formed and seedlings inserted singly.

Row spacings of 0.5 m and 0.75 m were found to be acceptable and yield comparisons showed seedlings to be similar to conventional planting for autumn/winter planting, but inferior for spring planting in the plant crop at one site. Ratoon yields were similar but cultivar differences were evident. Seedlings have become an established method of nursery propagation in South Africa, but because of the cost involved have not become standard practice for commercial planting. Seedlings have been found to be more sensitive to some herbicide combinations, and the timing of herbicide application as well as the treatment of seedlings has been adjusted to accommodate this. Cutting seedlings back at the time of planting and applying herbicides soon after planting have been found to be acceptable (McIntyre 1993).

The use of single eyed setts for direct planting is also under investigation. This system incorporates the use of mechanical planters adapted for the application of fungicides and insecticides where required, and this has the advantage of a substantial reduction in the amounts of chemicals required

for disease and pest control as they are applied to the sett and not the soil. Micropropagation techniques whereby certified disease free sugarcane plants are multiplied in vitro, hardened off, field planted and then propagated vegetatively are now being developed in various countries

(Snyman et al. 2008). Micropropagation of one apical leaf roll can yield up to 700 plants compared to 10 plants/stalk using the normal seedling route.

Choice of planting system

The choice of planting system is dependent on soil type, slope, region and a number of other factors.

An example of a planting system choice matrix is provided in appendix 3.