"It all starts with the soil."
That is what they say in organic farming. It's true even in conventional farming because soil doesn't simply hold your plants, it also supports them. Success in farming is largely dependent on the quality of your soil.
Unfortunately years of unsustainable agriculture practices have degraded the soil in many parts of the country and continent turning it into dust. The soil is now out of balance and unable to provide plants the conditions that they need to survive. So what has caused this you ask? Damaging things like planting the same crops in the same fields year after year, using too much fertilizer, tilling excessively, working wet soil and cutting down trees.
Our job as farmers is to support and optimize our soil so we can survive, grow healthy crops and get good yields. Healthy soils are critical for our farms' sustainability and commercial scale productivity. So let's start understanding our soil so we can better manage it.
What is soil?
The first step in improving your soil health is to understand soil. Soil is made of minerals, air and water and organic matter. Air, water and minerals make up most of soil ( 95%) and organic matter makes up (5%). For soil to be healthy it needs to chemically, physically and biologically healthy.
Signs of good soil health include increased organic matter, increased water holding capacity, balanced and diversified soil biology and increased water filtration. Moisture in the soil builds organic matter and fertility. Vigorous plants with strong roots and abundant soil organisms (e.g. earthworms) are signs for good soil health. Soil colour is another good indicator of soil health. Dark brown, red and tan soils indicate good soils. Soils with plenty of humus are dark in colour.
A sign of poor soil health is soil with a thin surface layer of topsoil which is prone to soil erosion. A thin surface layer makes it hard for plants to establish strong roots to support plants and grow healthy crops. Other signs of poor soil health include stunted roots and few living organisms.
You can't change your soil type but you can improve your soil structure, density and compaction.
Types of Soils
Determine your soil texture and structure. The relative proportion of sand, silt or clay in soil (texture) influence the soil water retention, air drainage and fertility:
Peaty Soils: soils rich in organic matter. They are black or very dark in colour. These soil feel spongy. Pros: easy to work, makes good seedbed. Cons: can be very dry in the summer, only for acid loving plants.
Clay Soils: appear and feel sticky and heavy, they are rich in very tiny particles, hold together well in a ball. Pros: can be rich in plant nutrients and water. Disadvantage: roots may find it difficult to penetrate soil and reach nutrients.
Sandy Soils: feel gritty, make rasping sound. Light sands that do not clump well if squeezed. Pros: warm up quickly, easy to cultivate. Cons: usually less fertile and low in nutrients, water drains away rapidly, often washes out nutrients with it.
Silty Soils: scapy, and very silky feel. They contain medium sized particles. Pros: reasonably moisture retentive and nutrient rich. Cons; compact easily, can be heavy to work.
Saline Soil: are found in arid regions, they have high pH. Pros: none. Cons: high salt content harms many plants, gypsum may help.
Why build healthy soil
The effects of our increasingly erratic weather conditions due to climate change are extensive in our region. We have faced multiple years of drought which has caused crop failure. This has made it even more important now that we focus on building healthy soils. Healthy soils are high in organic matter and microbes. Healthy soils have good soil structure and can retain water well and provide nutrients to growing crops.
How to test your soilTo produce the best result you need to begin with a soil test.
You can use a simple do-it-yourself test kit such as the LaMotte soil test kit or send your soil sample to a recognized testing lab. If you decide to go the lab route, which we suggest you do, we recommend Kutsaga Research Board or ZIMLABS.
Soil testing costs between $15-$25. Choose a lab that can best provide you with a complete soil test and final report. Your analysis gives you information about your soil content such as potassium, phosphorus, pH and organic matter content.
Your soil pH is the acidity or alkalinity of your soil. It affects your plants' uptake of nutrients.
Soil pH ranges from a scale of 0-14:
- a pH of 7.0 is neutral
- a pH below 7.0 is acidic
- a pH above 7.0 is alkaline
Most plants and vegetables prefer prefer a pH range of between 6.0 and 6.8. But plants are different and different plants prefer different pH. Potatoes like more acidic soil (5.5 - 6.0 pH).
Test your soil every year at around the same time so you know what your soil's nutritional requirements are.
How to collect a soil sampleTo get accurate soil test result you need to send your lab well collected soil samples. Soil sampling is the process of collecting soil from a field you want to farm so you know the condition of your soil. It is an important and often overlooked step in farming.
You can sample your soil at harvest time or before planting. You should try to have enough time for sample analysis, data interpretation and fertiliser recommendations.
- Using a shovel or trowel collect soil samples from a consistent depth (plough depth/ 6" deep for cultivated area) from at least 15 different places across the field you are sampling. Move either diagonally or in a zig zag pattern across the field.
- Mix the soil cores or sub samples thoroughly in clean plastic container/bucket and let them naturally dry out.
- Place the mixed sample in a plastic bag and put it in the bag provided by your soil testing laboratory for shipment.
- Label the soil sample with your name, address, contact number, farm address and crops you plan to grow
- After analyzing your soil the lab will send results of their analysis, as well as recommendations for improving your soil.
Strategies for building healthy soil
To improve your soil you can implement the following improved soil management practices. Please note that changes in your soil will not happen overnight or a season, but it's still worth getting started:
1. Add organic matter
The best way to improve your soil structure is to add 5% organic matter (about 1 inch). Adding organic matter such as well rotted manure, compost, peat moss and compost tea will increase your soil's tilth, texture, nutrients and microlife. The best of these organic materials is compost. Organic matter can be an important part of your fertility program. It can also help reduce you dependence on costly chemical fertilisers. You do need to test to make sure your soil is getting all the nutrients it needs.
2. Plant cover crops
Plant cover crops such as legumes (beans) or alfafa to keep the land covered. Cover crops increase the amount of organic matter in the soil, stimulating its ability to hold nutrients.
3. Cover soil with mulch
Keep your soil surface covered with mulch. Mulch is chopped straw, hay, wood chips, and or leaves. The soil benefits from mulch which helps suppress weeds and holds down soil humus. Mulching also decreases evaporation and protects the soil from soil erosion from wind or water.
4. Add minerals
They are several soil amendments that can rebalance your soil pH and mineral imbalances. For example if your soil is too acidic you may need to add organic matter and dolomitic lime; if its too alkaline you may need to add sulphur and organic matter. Add soil amendments such as fertilizer blends, lime and sulphur based on the recommendations of your lab. Adding too much of a particular nutrient may damage plants or interfere with uptake of some other nutrients.
5. Practice shallow tillage
Heavy tillage degrades the soil and disrupts microbes. Heavy tillage on marginal land can cause soil compaction. Compacted soil result in poor root growth. Shallow tillage or no till farming minimises destruction of your soil structure. Also time your tillage for times when your soil is not too wet,
5. Rotate crops
Don't plant the same crop in the same place all the time. Plan your crop rotation. Rotate plants from other crop families into that location so that you don't get disease build up. Diversifying your crops is good for your land.
7. Plant trees
It's actually better to not cut down trees, but failing that let's at least plant trees. Planting trees will reduce soil erosion and encourage rain.