Monday, August 20, 2018

Increasing maize yield levels per unit area (productivity) is the major driver as far as achieving food surplus is concerned in Zimbabwe. Improving maize productivity has immense benefits to the farmer and the nation at large. Basically, what high productivity level means is that a farmer will be producing more for less in terms of fewer resources (variable costs) and less land area, which has positive implications on enterprise profitability and sustainability. At farm level, increasing yield per unit area helps reduce cost of producing a tonne of maize grain.

This article gives an account of the 11 fundamental keys to achieve better yields. The 11 points are enunciated by Good Agronomic Practices (GAPs) principle, and it is our belief that this can significantly change the maize crop farming landscape for the better. It can be done!

Start with a well-conditioned soil

Soil pH is an excellent chemical indicator of soil quality (acidity/alkalinity) and its ability to avail nutrients to the crop. A well-conditioned soil has high Fertiliser Use Efficiency (FUE). Liming generally ‘sweetens’ acidic soils by correcting pH to optimum levels. The optimum pH range for maize is 5.5 to 6.5 based on a Calcium Chloride scale.

• Lime reduces availability of toxic elements in the soil such as aluminum and manganese.
• Liming improves the soil physical structure, resulting in good crop emergence and stand, greater root proliferation and an improved nutrient uptake.

The importance of soil conditioning in the regards of nutrient uptake efficiency/FUE can be explained in the table below:

NPK uptake efficiency vs pH levels

Key

It is therefore important to maintain or condition soils to optimum pH levels (5.5 to 6.5) for maize. This can be achieved by liming following recommendations from soil analysis results.

Start on a well-prepared seedbed

Thorough land preparation is essential in maize if the crop is to be grown productively and profitably. In fact, successful crop establishment is centered on good land preparation. Conventional land preparation should target the following aspects:

• To loosen the soil and to form a fine tilth-this aids good seed-soil contact and emergence
• To control weeds and start on a weed free seedbed
• To conserve moisture and improve drainage and water movement in the soil.

It is recommended that depth of tillage should be altered periodically to avoid plough pans or compacted zones developing. This will affect water infiltration, root development, and yield. Once in every three years, a farmer must come in with a ripper or chisel plough to break the pans. Tillage should also aim to retain and incorporate previous crop residues which aids Soil Organic Matter build up.

On the other hand, conservational tillage procedure aims at minimising soil disturbances and leaves at least 30% of previous crop residues on the soil surface after planting. It may include the use of tines, chisels and then followed by direct seeding equipment. It may also entail the use of zero till planters to sow seed directly without tilling the land. This has been shown to have significant advantages: improved moisture retention, rainfall/irrigation absorption (due to protective litter on the soil surface) as well as minimised erosion.

However, Conservational Tillage is mostly suited to soils with at least 25% clay content in the top 30cm zone. Soil structure and fertility must be good and balanced, pH must suit the crop to be grown, sub-surface compaction must be eliminated first; are the other prerequisites before adopting this concept.

Start with the right seed variety

Several studies have indicated that choosing the right seed variety contributes significantly to increased yields per unit area. In fact, a maize bumper harvest begins with choosing the right hybrid seed variety. Farmers should always select hybrids which couple high yielding ability and good defensive agronomic traits that make them adapt to the current climatic and biotic conditions. Productive farmers target the right variety for their ecologies and use only certified seed for assurance of performance. SC 727, SC 719, SC 637, SC 633, SC 649, SC 608 and SC 529 are top end yielders and have demonstrated high yielding ability in farmers’ fields. Selecting the right hybrid seed is one of the most important management decisions a farmer can make in a season.

Aim to achieve an optimum population and even stand

One of the most critical factors in achieving higher yields is establishing an optimum population that allows a hybrid to maximise its yield potential. Farmers are encouraged to always aim to achieve optimum population levels depending on varieties, rainfall and nutrition related conditions. Farmers are advised to follow practices that will enhance stand establishment. Adjust seeding depth according to soil conditions and monitor planting depth periodically during the planting operation and adjust for varying soil conditions.

• Always make sure the planter is well calibrated and in good working condition.
• Inspect and adjust the planter to improve crop stand establishment.
• Operate planters at speeds that will optimise seed and fertiliser placement. Uneven emergence affects crop performance because late emerging plants cannot compete with larger, early emerging plants.
• In high potential/irrigated environments, a final stand of 50-60 000 plants per ha can be targeted on most varieties from the 500 to 700 series, whereas population densities of 37-44 000 plants per ha are recommended in low rainfall potential areas.

Available phosphorus

• The rate of growth of a maize crop is dependent on Phosphate reserves. Deficiencies retard growth, giving stunted growth and low yields. Ideally, 30-50 parts per million (mg/kg) of available Phosphate is considered adequate for successful maize production. Available Phosphate is also affected by pH and in such a case, lime must be applied to correct acidity first, then straights such as Single Super Phosphate, should be broadcasted and incorporated prior to crop establishment.

Time of planting

• The time of planting has a major effect on the yield of a maize crop. For a summer maize crop, early planting at the beginning of the rainy season is advisable, as yields decrease with late planting and this is primarily due to decreasing daily Heat Units (HU) as the growing season progresses. It is advisable to always plant with the first effective rains, generally equivalent to at least 35mm rainfall received within three days. After the first week of November, the yield loss is above 100-120 kg per hectare per each delayed week. Maize growth rate responds well to high daily temperatures experienced in October, November and December. At least 40% of the HUs are experienced during these three months, so it is critical for farmers to plant their crop as early as possible to capitalise on the HUs.
• Generally, a maize crop that is planted before the main rains start have more vigorous root system hence it is beneficial to plant early. Planting early also lengthens the growing season. If irrigation is available, planting can commence as early as the first week of October.

Weed and pest control

• It is important to start with a weed free field especially for the first 10-12 weeks of a maize crop cycle as this is the period when more than 60% of the available nutrients are used/required by the crop. So, competition from weeds must be kept to a minimal or to null. Weeds during this period have a dramatic effect on yields. It is generally advisable to maintain a weed free maize field throughout the growing season. The national annual maize yield loss as a result of weeds is substantial. Generally, failure to control weeds during the first five weeks of the crop cycle leads to a 50% yield reduction. If a farmer fails to control Shamva grass throughout the growing season, yields can be reduced by 57-80%.
• Fall Armyworms is proving to be a menacing pest, which threatens farmer productivity and the food surplus drive which the country is in. Farmers should scout fields every 2-3 days and make spraying decisions early and with the appropriate registered pesticide.

Soil Organic Matter (SOM) build up

• SOM exerts numerous positive effects on soil physical, biological and chemical properties. SOM increases soil fertility by providing cation exchange capacity and acting as reserve of plant nutrients, especially nitrogen (N), phosphorus (P), and sulphur (S), along with other micronutrients, which are slowly released upon Organic Matter mineralisation. As such, there is a significant positive correlation between Soil Organic Matter content and soil fertility and ultimately yield. Tillage should therefore aim to retain and incorporate previous crop residues which aids Soil Organic Matter build up.

Moisture management

• Due to climate change, water is increasingly becoming a limiting factor to yields. High yields of maize often in excess of 11 tonne/ha can be achieved with irrigation. Where irrigation is available, higher yields can be obtained through early crop establishment before the onset of the rains. Supplementary irrigation applied during extended mid-season dry spells can lead to substantial yield increases. Irrigation can also be applied to minimise yield losses due to terminal droughts. Thorough land preparation also aids moisture conservation.

Address soil fertility issues

• Fertiliser programmes for individual lands must be adjusted in accordance with the respective soil fertility status. Achieving high maize yields requires an excellent soil fertility management programme which is centered on adequate timing and placement of Nitrogen, Phosphorus, Potassium and other micro-nutrients.
• Basal dressing should be applied at or before planting, while top dressing should be applied between 4 and 8 Weeks After Crop Emergence. Split applications of top dressing fertilisers are recommended in lighter soils (with clay content of less than 25%) i.e. sandy and sand loamy soils.

Never underestimate the value of crop rotations

• We can make a strong case that adopting crop rotation enhances crop yields. This is because crop rotation improves soil properties and greatly reduces risks associated with numerous weed, disease, and pest carryovers.

Parting shots

• The most important ingredient farming requires is personal involvement-how much-presence time- do you invest in your farming enterprises? The best fertiliser a farmer can have are his footmarks in the fields. Be a crop doctor, who observe the crop regularly and know what the crop requires. The crop should dictate what happens on the farm. The crop must call the shots!
• Always have the stability and consistency in yield growth. This is a key fundamental which makes the farming enterprises sustainably profitable. It can be done! Plan, Prepare, Procure, Plant, Pray-the 5Ps.
• Contact: +263 772 413 184/john.basera@Seed Cogroup.com/www.Seed Cogroup.com/zw or twitter: @basera_john or @Seed CoGroup
• Author: John Basera, Agronomy and Extension Services Manager at Seed Co