Roots 'n' Shoots: Sustainable, Productive and Economical Vegetable Gardening (Part 2): Conservation Agriculture

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Saturday, 13 September 2014

Sustainable, Productive and Economical Vegetable Gardening (Part 2): Conservation Agriculture

Winter vegetables
at peak production

1 maintained for long periods of time
2 use of natural resources without environmental damage

1 producing crop yield abundantly and efficiently
2 being worthy or satisfactory

1 making the most of resources
2 inexpensive
3 avoid unnecessary waste
4 efficient use of time and energy

* Definitions according to the English Encarta Dictionary

These three words are central to my veg garden endeavours and I am constantly improving on these in my growing practices. I have been reading (and have several books) about organic vegetable gardening [now again to clarify, *organic* in the sense of ‘derived from living things or sourced naturally’] but I found that the amount of ideas/information to be limited and that the integration of these ideas as a whole is lacking.

Firstly, organic = expensive, especially when it comes to purchasing these things in South Africa. Example: Seaweed based fertilisers, are very organic and very expensive (when compared to synthetic ones)....

Secondly, organic also means hard to come by (again with respect to South Africa), for instance: Neem oil as a natural pesticide is not readily available on the SA market...

Meaning that most of the options available for South African vegetable gardeners to be organic is either expensive or unfeasible. Therefore, on a shoestring student budget I have to come up with many different or creative ideas on how to achieve organic vegetable gardening. These experiments don’t always work out so great (such as my attempt to grow edible mushrooms failed miserably! LOL!)… but once in a while I manage to stumble upon something really cool and useful. 

I have been doing research into some of the sustainable practices in commercial agriculture and came upon a system (not new by the way) called Conservation Agriculture (CA). With a little patience and planning it can actually work very well in small-scale or backyard garden!

Some of the principles behind Conservation Agriculture (CA) was developed by an agronomist, Edward H. Faulkner in 1943, but was only built upon and fully established years later in the 21st century by various specialists. It aims to increase crop productivity through improved soil health and to reduce the environmental impact of agriculture. Well executed research has been done on the benefits of CA as opposed to more conventional methods (see references listed below). 

Conservation Agriculture has three major principles:

1) Reduced or no tillage: 

Traditionally, tillage or digging (by plough or spade) is meant to break up the soil, allow water to infiltrate and to incorporate nutrients into the soil. It also allowed a way for farmers to easily control weeds and soil-borne disease. In an agricultural sense; digging only allows temporary relief from compacted soils and lower soil layers become more compacted by the weight of heavy machinery (or human bodies standing atop). The long term effect of tillage actually destroys soil structure and causes soil erosion when the bare soil is exposed to wind and rain. 

One of the most ancient tools in agriculture
The Yorck Project
 10000 Meisterwerke der Malerei
DVD-ROM, 2002
ISBN 3936122202
Distributed by DIRECTMEDIA
Publishing GmbH Tomb of Sennudjem
Wikimedia Commons

 In CA, the soil is not tilled or tillage is kept to a minimum, some farmers have even returned to animal-drawn systems to decrease the weight on their soil and have set up permanent foot-traffic areas to prevent soil compaction in the fields. No-tillage allows the soil to remain undisturbed and builds up beneficial populations of soil flora (smaller plant based life) and fauna (arthropods, insects, earthworms, fungi, bacteria and other micro-organisms). No-tillage in combination with a ground cover and crop rotation improves overall soil structure and fertility in the long-term, so much so that in some cases it can out-produce conventional farming methods.

2) Semi-permanent or permanent soil cover:

Generally, cultivated soils (this goes for large-scale agriculture and smaller backyard gardens) are left bare. This exposes the soil to wind and water run-off that does away with your precious nutrient-rich topsoil. Heavy downpours compact the soil and reduces the amount of air pockets inside, which results in poorer water infiltration. Bare soil with large amounts of clay (or even clay poor soils) are more prone to compacting after the winter chill, which results in additional tillage come spring.

Living mulch: Lesser or suckling trefoil (a type of clover)
Trifolium dubium 

A semi-permanent or permanent soil cover by either a permanent stand of crops or green manure or mulch (dead or alive) is essential to improve soil structure. Even a protective cover of 30% derived from crop left-overs is better than to leave it bare. A soil cover keeps down weeds, prevents soil erosion and compaction, through both plant and microbe activity, which increases soil health in the long run. Soil cover provides food for beneficial soil organisms (mostly microscopic fungi and bacteria associated with plant roots). These organisms break down, 'biologically till' and incorporate nutrients from the cover crop back into the soil. Effectively building up layers of undisturbed, nutrient-packed topsoil that isn’t blown away, washed away or lost through leaching (nutrients move into deep layers of soil where they become inaccessible to plant roots).

3) Crop rotation:

Conventional agriculture results in mono-cultured crops, this means large stands of one type of plant species. After several years of planting the same crop in the same soil results in an increase of soil-borne diseases specific to that crop and depletes the soil of certain nutrients. Large crop stands are also easier for pest insects to find; resulting in massive crop losses when pests spread like wild-fire through the fields. Sickly mono-cultured crops are also less resistant and become easily over-run by weeds. To improve crop production, synthetic Nitrogen (N element) fertilisers are used in an attempt to replenish the soil, whereas large amounts of pesticides and herbicides are used to combat pests, diseases and weeds.

Now, you have all likely heard the outrage from all sectors about the use of synthetic fertilisers, pesticides and herbicides, but never got told properly why these products are so bad – you are just supposed to believe all the ranting. I don’t use any synthetic herbicides or pesticides in the garden because most are ‘general’ products. This means that they do not distinguish between beneficial plants (like vegetables) or insects (like bees) as opposed to pest species (such as weeds or aphids), they simply kill everything. Those that are specific (say for aphids only) are generally toxic and have withholding periods before the crops treated with these can be used again. Pesticides/herbicides are very ineffective at controlling pests and weeds. Only 50% of pesticides sprayed over crops through air-crafts actually reach the target crop and in general less than 0.1% of pesticides reaches the target pest, meaning that 99.9% of it is lost and contaminates the environment. Considering that herbicides and pesticides are not ideal, gardeners and farmers can still use them with reduced environmental damage by using them in the correct way, see my post on this issue.

The Nitrogen Cycle

I will discuss synthetic N fertilisers as well. The same principle of correct use that applies to perticides/herbicides applies to N fertilisers: the overuse or misuse of synthetic N fertilisers results in serious environmental damage and leads to cultivated soil destruction. When N fertilisers are combined with irrigation, 30-50% of N is lost through leaching! N fertilisers should be added to the soil as they are needed, by chemically testing the soil and applying what is deficient, but this is rarely done in agriculture or in vegetable gardens. The unfortunate result is that an excess of synthetic N disrupts the microbial activity in the soil. These organisms switch to using up all the Carbon (C element) in the soil and then storing large amounts of N in the soil. What this does is deplete nutrients, reduces soil available carbon (organic matter) and builds up nitrogen; leading to acid and salty soils (known as acidification and salinification). Acid soils cause more nutrients to become unavailable to plants and limits the healthy growth of plants. Convention then would lime the soil to correct this, but only results in a downward spiral towards destroying the soil completely until it can no longer be used for crop production. Some of South Africa’s cultivated soils have become so laden with salts (nitrates derived from nitrogen) that only salt-tolerant crops can be grown in them (See my table below for stats)!

South Africa cultivated soils (2009):

Land usage
Percentage (%)
Acidified cultivated
Arable = cultivated = used to produce crops
Thus, already 51.6% of arable soil has been destroyed through conventional practices, if we don't switch to sustainable means how would we feed all our people?

In order to provide an alternative to synthetic N fertilisers and to improve soil fertility, crops are grown in rotation in CA. Here I am referring to crop rotation, multi-cropping, mixed species cropping and inter-cropping at the same time. Basically, crop rotation is the planting of two or more different plant species in the same field, preferably at the same time, in the same year. What farmers do is it to plant two important food staples, such as wheat and potatoes together with a legume crop, such as beans. In a simple system, you have 4 fields and three fields would be planted with one of each crop and the last would remain empty of crops (fallow) but covered with mulch. These are rotated every six months to prevent nutrient depletion and pest build up. Wheat and potatoes use different nutrients, whereas beans replenish soil N through its association with specialised root bacteria (Rhizobia species). The fallow phase (empty) allows other nutrients and carbon to be returned to the soil, as well as improving its structure through microbial activity. REMEMBER, the fallow phase will still have a protective soil cover, just no harvestable crops!

Simple crop rotation system in agriculture

Conservation Agriculture has been very successful in Brazil and Mexico where some farmers where able to exceed conventional crop production whilst improving their soil health with every rotation. 

I am very keen on implementing this in my garden, but I would like to recommend a few things and discuss my overall plan:

1) No tillage: This is awesome and works great for me seeing that digging over the garden is a literal back-breaking experience. If your vegetable garden has or you are starting off with poor soil fertility and poor soil structure I would recommend some tillage at least until the soil doesn’t compact on its own after winter. Then you can comfortably switch over to no tillage and let the microbes do the rest! The time needed before no tillage will be greatly minimised by applying your permanent soil cover and crop rotation schemes!
No tillage saves on time and labour (and money for farmers due to less fuel expenses). The planting of seeds is immediate with no ‘working’ of the soil needed beforehand after the fallow phase has expired.

2) Permanent soil cover: I already mulch with dried grass clippings from the lawn, but I find that there isn’t enough grass clippings for the veg garden and for chicken coop litter. Also, nasty critters by the name of Cutworms live in the grass clippings and every time I mulch I am adding these to the garden! The Horror! I am now moving into a green mulch or ground cover, specifically penny royal between my veg plots and clover inside my veg plots. The penny royal has been very successful, see post – I am still working on the clover and will post updates on that later!

Alternatively you can incorporate other green manures and cover crops into your garden. If you have chickens you can choose green manures that dual as chicken feed! See post on Green Manures and Cover Crops. When you want to plant seedlings or sow seeds, simply lift out a piece of your green manure/cover crop and re-plant somewhere else or feed to the chickens.

 Green manure & cover crop
Medicago sativa

3) Crop rotation: I have been rotating my crops since the start of my vegetable garden, but the recommended crop rotations (i.e. root plot, leafy veg plot, solanum plot and cucurbit plot) doesn’t really work in small veg gardens; it also doesn't work if you have more/less than 4 plots - I have 7 which makes rotating between 4 types confusing at times... So I will now opt for mixed or inter-planting, where I plant a tomato here and there with a few radishes and beets in between and maybe some parsley and onions… I think that this will create a more dynamic planting scheme, both considering the above ground canopy (tomatoes provide some shade and protection to lower growing crops) and underground system where different root structures occupying one plot. This increases diversity in plants, beneficial insects and soil microbes and should either confuse pests or prevent disease. I will do an update on this method later as well.

Mixed or intercropping of fennel, spinach and lettuce

Alternatives to herbicides, pesticides and synthetic fertilisers: I don’t use any herbicides, I either pull them by hand or plant penny royal to out compete them where they grow (clover will have the same effect). I don’t use any pesticides, I either use green recipes (Pest Control Page), biological control or remove them by hand (which is what I do if the beneficials don't get to them). I have been using synthetic fertilisers, but after reading all the research I have decided to start phasing out these as well and replacing them with more natural alternatives, such as Comfrey, Earthworm Tea and Chicken Manure, Alfalfa and Clover

You can also check out the Talborne Organics website for their wonderful range of organic fertilisers and pest control productsFor vegetables and fruits I would recommend the Vita - Flower & Fruit, which is a slow release 3:1:5 NPK that you can add to your plots, whereas the Biogrow Biotrissol is a liquid fertiliser with similar NPK ratios of 3:2:5 (the liquid one you can add every two weeks at half strenght to all actively growing fruit and veg). Talborne Organics have an extensive list of distributors around South Africa and should be easy to come by.

Hover fly (Diptera) visiting Pak Choy flowers

Last notes:

Clover is also a legume and able to fix nitrogen (it is related to Alfalfa), see Green Manures, and therefore it is a built-in biofertiliser already active in the garden! The nutrient legumes fix are added to the soil through their residues or addition to the compost heap. I will be on the look out for more alternatives in the future and will post what I come across.

I am very interested and excited to see the results of my ‘new’ vegetable garden management routine and will be sure to keep you all updated. I hope this article has inspired you too and please let me know of your results if you also choose to implement a similar system (or have already)!

All my references (freely available), for further reading:
1) From the WWF (SA) – Agriculture: Facts and Trends South Africa.

Some good information on ‘best practice’ agriculture principles and scary stats on the condition of South Africa’s cultivated lands.

2) From the Agricultural Research Council (SA) – Sustainable Land Management Practices in South Africa (2009)
Information on Conservation Agriculture and other sustainable practices as well as results from on-farm implementation.

3) HOBBS, P. R., K. SAYRE and R. GUPTA, 2008 The role of conservation agriculture in sustainable agriculture. Phil Trans R Soc B 363: 543–555.
An excellent scientific article reviewing Conservation Agriculture and has an awesome table with all the benefits of CA as well as case studies in Mexico and Brazil.

4) MULVANEY, R. L., S. A. KHAN and T. R. ELLSWORTH, 2009 Synthetic Nitrogen Fertilizers Deplete Soil Nitrogen: A Global Dilemma for Sustainable Cereal Production. J Environ Qual 38: 2295–2314.
Another scientific article on the effects of overuse and misuse of nitrogen fertilisers

5) STOCKDALE, E. A., and C. A. WATSON, 2012 Managing soil biota to deliver ecosystem servicespp. 163. Natural England Commissioned Report.
A huge book jam-packed with information on how soil micro-organisms influence soil health, crop production and natural ecosystems.

6) PIMENTEL D. and M. BURGESS, 2012. Small amounts of pesticide reaching target insects. Environmental Development and Sustainability 14:1 1-2.
A two page article summarising the total amount of herbicides, fungicides and pesticides used by the US, how much actually reaches target insects and how expensive it is to maintain such practices.


Previous articles in this series: Sustainable, Productive and Economical Vegetable Gardening 

Part 1: Vegetables worth growing

- Update 14 September 2014 -

Here is an article regarding conservation agriculture in sub Saharan African and its impact on small holder farming communities;

IFAD social reporting blog: Does conservation agriculture work for smallholder farmers in Africa? New report highlights key points for action. Ricci Symons, 29 August 2014.


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  1. Hi Shroom,

    Excellent post. very informative.

    As mentioned before I am also trying to practice CA however it is quite difficult to do in small veggie patch. I am going to start using the penny royal and also clover now. What I do find very good as mulch at the moment is half decomposed garden compost that has a high wood content ( I have lots of shrubs and trees when pruned are excellent source of wood). I also plan this year not to plant the whole veggie patch at one time (difficult to do as I get too excited). I want to have at least 25% of veggie patch empty at all times and more constant production of veggies throughout the season.

    I must say that not digging in the soil and walking on it makes the work in veggie patch so much less. The only real tillage I do is when adding compost and I fork it in top layer with hand fork. And with the very hot weather we having it looks like mulch will be very important this summer.

    Also I don’t do crop rotation as planned as all the books tell me too. What I do is just try to make sure that I don’t plant the exact same plant ( not necessarily the same family) in the same spot for 3 years. I also like to add small flowering plants within crops and inter crop with veggies such as radish, beetroot, rocket and basil. What is working well to attract bees and wasps( eats aphids if I remember correctly) is 2 lavenders. They bloom all year and have made a very nice addition to my veggie patch.

    Anyway let me go. Will keep you updated.


  2. Oh almost forgot for readers of this blog that live in the westrand or anywhere actually a cheaper source of compost and mulch is the municipality garden and waste sight. They make own compost from the cities garden refuse. What is also nice is that you know there is no added synthetic ingredients in the compost and wood mulch is just wood chips not dyed with any dye.

    Shroom a normal bag of compost or wood mulch is R13.00. See link for address for closest one to me, Panorama Garden Site, Jim Fouche Road,

  3. Thanx Ross! I also recall that the farmers who convert to CA have a difficult time initially, especially with the weeds - thanx for the link to easy (and cheap) compost/mulch to come by seeing that a weed war is likely to ensue once you start CA, LOL!

    But, I do believe once the weeds are under control and the soil structure becomes more friable, the benefits of CA will really start to pay off. For instance, I have not used any organic pesticides for a year now (never used synthetic) and I have applied mulch for about a year and a half (not necessarily in a full CA setting)- and this year coming out of winter I have noticed a huge amount of earthworms in the plots as well as some new decomposers (specifically pot worms; the larvae of small midges). The soil still compacts a bit (we have naturally clayish soils), but I can very easily dig deep into the soil without using a spade these days, a huge improvement! The decomposers and soil structure improved more substantially during the small time I have been mulching than it did during its first few years without.

    Vegetable gardens are much like people, they become even better with age and TLC - my garden can support a lot more crops than it did in its first two years and each year I am amazed at the progress of the soil quality (more to the praise of the soil organisms than what I can do, LOL)...

    So, thanks for swinging by Ross and good luck to the coming growing season! [It really should rain now, I can't stand the heat and its only September! One day it was winter the next, summer - seems like spring is only a calender event now ;) ]


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