Roots 'n' Shoots: September 2015

Sunday, 20 September 2015

Natural (Bio)fertilisers & Living Mulches: The Edible Legumes

I have been running several posts on using plants as biofertilisers, living mulch and even chicken feed. This post is a follow up on the living mulches that I have been experimenting with. In my previous post on the topic I discussed Penny Royal as a weed barrier as well as several plants (which include many legumes) that can be used as green manures and green chicken forage.

The Penny Royal has done a awesome job at keeping weeds at bay in The Weed Zones that border the vegetable plots - but I wanted a living mulch to plant inside the vegetable plots as well. Preferably a legume to fix nitrogen and release the nutrient once it dies off (legumes do not share their nitrogen when alive!). It must, however, still be a ground cover so that it doesn't out compete the vegetables for light... hence after some research and looking at what is available in the nurseries - I had two choices: Red clover or White clover.

The other idea I had was, once I had big patches of clover (and if I needed to uproot some to plant new veggies) I could move the extra plants to the alfalfa patch - this allows more green forage for the chickens in winter. I also hoped to find both species so that I can have more diversity in the garden, but unfornutately the nurseries only stocked white clover.

The white clover (Trifolium repens) I acquired is a black cultivar sold under "Black Shamrock". It did a little poorly when I just transplanted it (winter last year) - it was a bit sickly, had chocolate spot fungal problems (a common infection for legumes so watch for signs on peas & beans!). It had a tough time during summer as well (very hot last season) - but it established and grew like a beast this last winter. The penny royal had died off in some areas during the last winter, which the white clover has encroached on - doesn't bother me either way... Here it is with it adorable white flower heads!


Similar flowering structures of legumes in the vegetable garden.


A 'wild' clover had made its way into my vegetable garden during the same time I transplanted the others. I noticed the subtle similarities in flower and leaf structure between the two. I took to some digging around the Internet dungeons to find that it was, Trifolium dubium (lesser hop trefoil or tick trefoil!). It has a less compact growth and its low branches spread outwards from a single plant. It carries a small cluster of yellow flowers and self seeds remarkably easily. The yellow clover has an additional bonus - it is more drought and heat tolerant than the white clover. By some selective weeding between the sour sobs (Oxalis sp.), which look very similar especially as seedlings, I managed to get  a good patch going. The seeds of the lesser hop trefoil (lets call it yellow clover for simplicity) is ripe when they turn completely black - you pick them off an sow somewhere else (likely only germinate in warm weather) or leave to self seed.


Similar looking weeds that grow naturally in the vegetable garden and how to distinghuish from clover species.


Whilst I was reading up on literature for my research project, I glanced over some articles pertaining to nitrogen fixation in alfalfa and clover. Legumes associate with certain bacteria in the soil, which infiltrate the roots and form nodules - this is where nitrogen is created and accessed by the plant. It is only during the death of these nodules that the nitrogen is released (along with the bacteria) into the soil. Interestingly I read that the bacterium associated with Soybeans is not native to South African soils and needs to be added to the soil by farmers through special liquid fertilisers! Here is a list of legumes I grow and their associated bacteria:

Legume
Species bacteria (bv. = biovar)
Pea
Rhizobium leguminosarum bv. viciae
Bean
Rhizobium leguminosarum bv. phaseoli
Alfalfa
Sinorhizobium meliloti
Clover
Rhizobium leguminosarum bv trifolii

All these legumes are not native to South Africa, but in some areas due to their widespread cultivation; natural and on-going population have become established in the soil. Also if you are fortunate enough to get seed inoculated with the bacteria there is a good chance for the plant to establish its own nodulating population. So this lead to some digging into whether or not my legumes would develop any nodules in order to fix nitrogen. Hence, some investigation! I promptly gathered up my camera and some digging tools and set out to the veg garden. I dug up each plant and recorded the nodule formation.





Yellow Clover nodules, be careful to uproot as nodules break off easily!

Images of legume roots and their nodule formation.
Longest nodules are indicated by the orange circles.

As you will notice the Peas and Beans have minuscule to no nodules, meaning that my soil lacks Rhizobium leguminosarum bv. viciae and Rhizobium leguminosarum bv. phaseoli. Therefore organic fertilisers are required to supply the Peas and Beans with enough nitrogen for healthy growth. The alfalfa and clover however are a different story - just look at the lovely nodules! Therefore both the clover and the alfalfa are generating nitrogen. Thus, during the death of the plants nitrogen is released back into the soil. The alfalfa plants are a permanent stand and would likely not release any nitrogen into the soil (they have many other soil building properties however), but the clover dies and resprouts the whole time. Therefore, each generation of clover helps build up the soil nitrogen! How cool is that?!

Since the establishment of my weed barriers and biofertilising crops over a year ago; the garden is (almost) weed free and with the help of the clovers my vegetable garden's soil should drastically improve over each successive clover crop. Therefore, legumes are an essential tool for organic gardeners by taking advantage of it being a living mulch, biofertiliser and chicken forage crop!

Now then - here is a sneak peak to my latest experiment - Peanuts! Just look at them nodules (Bradyrhizobium yuaminhense & B. elkanii, about 22 Bradyrihzobium spp. that associated with peanuts are native to South African soils)!!! I added a picture of Soybean nodules (Bradyrhizobium japonica inoculated soils) - forgot about measuring, but if I recall correctly they were anything from 1 cm to 3 cm. This is what healthy pea and bean nodules should look like too!


Healthy peanut and soybean nodules.

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Please share with fellow gardening enthusiasts via the various sharing buttons at the end of posts/pages! Else you can vote for posts through the Google reactions bar at the end of articles. To stay up to date I have provided several reader and social networking platforms with which to subscribe: TwitterPinterestRSS Feed Reader or Email/Follow directly using the Blog Followers widget on the left hand side toolbar. Thank you for reading and please feel free to ask if questions arise - I appreciate comments and ideas too! 😆
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Saturday, 5 September 2015

Solar Power in South Africa Part 3: Solar & Seasonality, Living with Solar in Gauteng, South Africa


How’s your Solar in Winter? (Author: The Economist)


Winter sneaked up on our solar electricity system during July. We hardly took notice of the change in the length of a day before installing solar and now it matters. We lose up to 6 hours in daylight from the longest day in summer to the shortest day in winter. That is a lot. The days shrink by almost 2 minutes per day, that’s about 20 minutes every 10 days! The result is that the supply of solar electricity shrinks as the days get shorter and the demand for reservoir electricity increases as the nights get longer.

The daylight and night time effects combine with a third negative, a drop in temperatures for a triple punch to the solar electricity system. The drop in temperature means that all heat based electricity needs increase and here I exclude home heating. The heat pump takes 3 hours to get the geyser temperature to 60 degrees when in summer it would take between 1.5 and 2 hours to do the same job. The kettle takes a few minutes more every time it is used. The dishwasher has to contend with much lower temperature water inflows to be heated up and the tumble dryer also has to work harder to dry the clothes. It all adds up to increased electricity demand when days get shorter and reservoir needs increase.


Winter is when you find out how robust (or not) your solar electricity system is. So, let’s look at supply of electricity from the solar panels.




There is one additional observation with regards to supply in winter which matters for us here in Gauteng South Africa. Winter sees atmospheric interference which causes hazy mornings and afternoons. So the solar electricity production is muted even with good sunshine at around 08h30. Once the hazy conditions clear up around 09h30 we experience a steep rise in electricity production. Sadly the loss of electricity generation due to haziness has a significant effect on total daily electricity production in winter and haziness is the norm not the exception, so we show hazy conditions on the graph as the “best” case. The electricity generation in winter is about 55% of summer generation with hazy conditions, but on clear winter days we can get around 65%-70% of summer electricity production.

Overcast days in winter are terrible for solar electricity production but fortunately Gauteng is a summer rainfall area with very few overcast winter days. We’ve discussed generator back-up in our first article here, Part 1: How to go off grid permanently (The System Set-up).


The change is season requires a resource management response from us. We have to use the electricity with more care with the most important effect having to spread the use of electricity. An example is not to do the washing only once a week, which requires the tumble dryer to run 4 times during the day but to spread the washing over two non-consecutive days. Thus, the tumble dryer runs only twice on those days. Demand management will be the subject of our next post.

Here is a table of our summer and winter electricity supply and demand data. Keep in mind that it applies to our system and our household needs, which for each household would differ.




Our solar electricity system can supply up to 56.5kWh electricity per day in high summer. We usually only need around 20kWh per day in summer on high use days, which means that we have surplus supply of more than double our needs. Here the “use it or lose it” principle applies so one can store it in ever larger battery banks or use it for unusual needs such as cooling the house (aircon) or processing of excess fruit and vegetables into jams or for drying (which uses the oven), etc.

In winter the picture changes fairly dramatically. We produce only around 31kWh electricity per day while a high use winter day can easily get to 28kWh. Our winter surplus now falls to only about 3kWh per day slightly more than a 10% surplus margin. Our daylight supply in deep winter is tight and our overnight reservoir is also under pressure. I’ve discussed the battery banks here, Part 2: Living with Solar in Gauteng, South Africa. Our solar electricity supply is adequate albeit tight as the few high winter weeks are manageable and soon after we are back to ever increasing surpluses as the length of days increase by 20 minutes every 10 days.

Sun position in the sky at 18h00 from January to December 2015
(read from- top left to bottom right). 
Notice differece in available light;
this has an effect on solar production throughout the year.
Picture generated with screenprints from Stellarium 0.11.2 software.

The solar experience so far is a positive adventure with no load shedding and with significant economic benefits!




Program reference: Stellarium - A free planetarium software, allows you to look up and track stars, planets and constellations in the night sky.


Our solar system was designed and installed with the assistance of Jurie Venter, cellphone 083 557 6031 and email jurie@sunor.co.za . For details on the whole system, see the post How to go off grid permanently.


Related Posts:

Part 1: Solar Power in South Africa - How to go off grid permanently (The System Set-up)
Part 2: Living with Solar in Gauteng, South Africa (Batteries)

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Please share with fellow gardening enthusiasts via the various sharing buttons at the end of posts/pages! Else you can vote for posts through the Google reactions bar at the end of articles. To stay up to date I have provided several reader and social networking platforms with which to subscribe: TwitterPinterestRSS Feed Reader or Email/Follow directly using the Blog Followers widget on the left hand side toolbar. Thank you for reading and please feel free to ask if questions arise - I appreciate comments and ideas too! 😆
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