In our pur­suit of the per­fect gar­den, we of­ten over­look the very thing it re­lies on. So how can we im­prove the health of our soil – and our plants?

Gardens Illustrated Magazine - - Travel - WORDS JOSHUA SPARKES IL­LUS­TRA­TION VICKI TURNER

As gar­den­ers we gen­er­ally re­gard our glo­ri­ous plants and well-tended de­signs with the ut­most pride, but below ground there is a whole other world in our care, a very se­cret and mys­te­ri­ous one. Per­haps more like a uni­verse, it is this which feeds our gar­dens, sus­tains our wildlife and gives us life on this planet, yet we over­look its stag­ger­ing com­plex­ity and im­por­tance in our ev­ery­day lives. This is the uni­verse of the soil, and more im­por­tantly the life within it.

Our soil is un­der threat on a global scale. Our planet has al­ready lost 70 per cent of its fer­tile top­soil, mainly through in­dus­trial agri­cul­ture in­creas­ing the rate of ero­sion. A United Na­tions re­port states that glob­ally we are los­ing 24 bil­lion tonnes of top­soil ev­ery year – that’s the area of 30 football pitches ev­ery minute. A re­cent govern­ment re­port claims that the UK loses around 2.2 mil­lion tonnes of top­soil ev­ery year. With this cur­rent tra­jec­tory we could lose most of our fer­tile soil in the next 60 years, and it is wor­ry­ingly most of this dam­age has only been done in the past 150 years. Among all the doom and gloom, you may be won­der­ing how this re­lates to you as a gar­dener.

The RHS es­ti­mates there are 24 mil­lion gar­dens in the UK and that is an in­cred­i­ble amount of land when added to­gether. It is

easy to sep­a­rate our gar­dens from the wider en­vi­ron­ment, to hear the plea of the nat­u­ral world but some­times still to act against our bet­ter in­stincts in pur­suit of per­fec­tion in our own space. But it is in our man­age­ment of the soil that we can make the most change. By al­ter­ing our meth­ods and pri­or­i­ties, we can make our gar­dens health­ier for all and change the per­cep­tions of what a good gar­den should look like. And per­haps the first step to take is to change our idea of what makes a ‘per­fect’ gar­den.

This is a no­tion be­ing tested in the USA with many in­sti­tu­tions and gar­dens shift­ing their idea of what con­sti­tutes a ‘per­fect’ lawn. Last year I vis­ited Chicago Botanic Gar­den, New York Botan­i­cal Gar­den, Brook­lyn Botanic Gar­den, Har­vard Univer­sity, Mount Cuba Cen­ter in Delaware and Chan­ti­cleer in Penn­syl­va­nia; not only do all these gar­dens ac­cept the odd clover in their lawns, but they use its ben­e­fi­cial qual­i­ties – re­tain­ing ni­tro­gen while pro­vid­ing fod­der for emerg­ing queen bum­ble­bees.

In the USA, as in Bri­tain, there is cur­rently a sus­tain­abil­ity re­nais­sance. The de­struc­tion of soil caused by in­dus­trial agri­cul­ture has led to great work be­ing car­ried out in re­gen­er­a­tive farm­ing. Both hor­ti­cul­ture and agri­cul­ture have a lot to teach each other on the topic of sus­tain­abil­ity. Research on the re­gen­er­a­tion of soil has found its way

into Amer­i­can hor­ti­cul­ture, help­ing to de­velop new prac­tices with some amaz­ing re­sults.

Rather than as­sess­ing the health of the soil purely in terms of its chem­istry – that is, ni­tro­gen, phos­pho­rus and potas­sium (NPK) – man­age­ment meth­ods now fo­cus more heav­ily on the bi­ol­ogy of the soil, the mi­crobes, bac­te­ria, pro­to­zoa, fungi and other micro­organ­isms. A sin­gle tea­spoon of rich gar­den soil can con­tain up to one bil­lion bac­te­ria and sev­eral me­tres of fun­gal fil­a­ments along with sev­eral thou­sand pro­to­zoa and ne­ma­todes. A pint of soil can con­tain as many or­gan­isms as all the hu­mans who have ever lived. Each plays a role, with nu­tri­ent-rich bac­te­ria be­ing con­sumed by larger preda­tors (pro­to­zoa and ne­ma­todes), which in turn re­lease nu­tri­ents back into the soil for use by plants.

The use of my­c­or­rhizal fungi in gar­den­ing has seen a huge in­crease, and for good rea­son. When part­nered with a plant, the fungi can in­crease wa­ter up­take by 40 per cent (in­creas­ingly rel­e­vant as our cli­mate changes) and strengthen the plant to fend off at­tacks from pathogens. En­cour­ag­ing the na­tive my­c­or­rhizal fungi in your own gar­den is likely to give far bet­ter re­sults than us­ing the com­mer­cial prod­uct, as ‘na­tive’ fungi have higher sur­vival rates when re­leased back into the gar­den from which they came. In fact, cer­tain places now fol­low a form of cul­ti­va­tion called Nat­u­ral Korean Farm­ing (NKF), which is based on the idea, first de­vel­oped in Korea, of grow­ing and us­ing your own na­tive mi­crobes, es­pe­cially fungi.

The Chicago Botanic Gar­den has an en­tire depart­ment ded­i­cated to mi­cro­bial life in the soil. There is a test plot that tracks the ef­fec­tive­ness of mulches, bio-char and com­post ex­trac­tions in gar­dens. Com­post ex­trac­tions work by re­mov­ing a sam­ple of mi­cro­bial life from com­post through an aer­o­bic wa­ter sys­tem, a process known as ‘brew­ing’. This in­creases the mi­cro­bial pop­u­la­tions then ap­plied to the soil. The re­sults are di­rectly linked to prac­ti­cal work in the gar­dens.

Or­ganic fer­tilis­ers and liq­uid feeds such as sea­weed pro­vide a good al­ter­na­tive to syn­thetic fer­tilis­ers such as phos­pho­rus. The min­ing of phos­phate rock it­self is un­sus­tain­able. Soil is dam­aged dur­ing ex­trac­tion, ero­sion and com­paction re­sult and green­house gases are re­leased. Much of the phos­phate leaches into wa­ter sources, poi­son­ing them and the sur­round­ing soil. In any case, phos­phate re­serves are pre­dicted to run out by 2030.

It is now more ur­gent than ever that we use sus­tain­able prac­tices in our gar­dens. The one thing we do know is that there is no sil­ver bul­let or sin­gle an­swer to any of this. To make our gar­dens truly sus­tain­able, we must start to ques­tion our gar­den­ing prac­tices and learn from cur­rent research. The uni­verse be­neath our feet is very much hid­den from us, but if we want our gar­dens to re­main for fu­ture gen­er­a­tions, we need to start look­ing deeper.

USE­FUL INFORMATION Four good books on the sub­ject are The One-Straw Revo­lu­tion by Masanobu Fukuoka (NYRB Clas­sics, 2009), The Soil Will Save Us by Kristin Ohlson (Ro­dale, 2014), Prac­ti­cal Or­ganic Gar­den­ing by Mark High­land (Quarto, 2017) and The Biochar De­bate by James Bruges (Green Books, 2009).

NEXT MONTH Joshua of­fers a prac­ti­cal guide to get­ting the best from your gar­den soil.

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