SOIL

6 things ev­ery farmer needs to know about In try­ing to fig­ure out the cause of a poorly-per­form­ing pas­ture, Ruth digs up cru­cial in­for­ma­tion about soil.

NZ Lifestyle Block - - Down On The Farm - RUTH REN­NER

Ex­plor­ing soil has turned into a far larger and vastly more in­ter­est­ing ex­er­cise than I an­tic­i­pated. I have con­se­quently failed to do what I set out in last month's col­umn be­cause I got car­ried away on a tan­gent and put off study­ing the hard bits of soil science in favour of the fas­ci­nat­ing story of what's liv­ing in the soil and mak­ing it all work.

We did get all our soil test re­sults back and some rec­om­men­da­tions for fer­tiliser. I've in­cluded those at the end (see page 43), but I'm go­ing to tell you about the more in­ter­est­ing stuff this month, be­fore I get to grips with the chem­istry the­ory later.

I used to think soil was the brown stuff which just lay there un­der the more in­ter­est­ing plants. But it's one of the most fas­ci­nat­ing ecosys­tems there is. It's ab­so­lutely teem­ing with life­forms, all in­ter­act­ing with each other as providers of food, ei­ther in and of them­selves or be­cause of the pro­cesses they ex­ert on other things.

We can in­flu­ence what goes on there for good or ill, and most mod­ern farm­ing tech­niques have pri­mar­ily done the lat­ter.

Nearly ev­ery farmer I have spo­ken to tells me they know less about their soils and soil in gen­eral than they feel they should. Why don't we know? Is it that the fer­tiliser in­dus­try has con­vinced us that it can solve any prob­lem we per­ceive from above, so we don't need to bother with what's go­ing on un­der­neath? If your grass isn't green enough, it ob­vi­ously needs fac­tor X, so here, let me sell you this bag of chem­i­cals or spe­cial in­gre­di­ents to ad­dress that short­age.

We like the quick fix, es­pe­cially when we're busy and there are seem­ingly more im­por­tant things to be done, so we've ab­di­cated re­spon­si­bil­ity for un­der­stand­ing the needs of our own soils.

Then there's all that com­pli­cated stuff like Cation Ex­change Ca­pac­i­ties (CEC) and Base Sat­u­ra­tions (BS). For those of us who are a long way in time from our for­mal chem­istry ed­u­ca­tion, it all seems like an im­pen­e­tra­ble wall of gar­ble.

This col­umn was in­tended to be a "this is what we found and this is what we will do to fix it" an­swer to last month's mys­tery of my vari­ably pro­duc­tive pad­dock. But as I read and re­searched and thought about the things I had dis­cov­ered, I re­alised that although that's what we all want to know about things which aren't quite right, bi­o­log­i­cal sys­tems don't work like that. There are no in­stant fixes, and al­ways a com­pli­cated web of con­trib­u­tors.

Air, wa­ter and bi­o­log­i­cal ac­tiv­ity are in­te­gral to the make-up of soil. If soil was sim­ply clay, sand and silt, any fer­tiliser we put on it would mostly wash through and out into the ground wa­ter.

It is the life in the soil which holds the nu­tri­ents in their bod­ies (many of these are only one cell) and in the sub­stances they ex­ude as they live, and from which plant-avail­able nu­tri­ents are then re­leased as waste prod­ucts, or as the or­gan­isms die or are eaten by oth­ers.

A very ‘lively’ soil will be ro­bust and able to stand up to too much wet, long pe­ri­ods of dry, the tread­ing of an­i­mals and so on, all the things we need from farmed land.

I've al­ways thought of earth­worms as the rep­re­sen­ta­tives of what­ever is go­ing on, un­seen and un­known, un­der­ground. As it turns out, earth­worms are a very good in­di­ca­tor of soil health, be­cause they eat a lot of the stuff we can't see - lots of bac­te­ria,

pro­to­zoa, ne­ma­todes and or­ganic mat­ter. If there is lots of food, there will be lots of worms. If there are lots of worms, they are do­ing a huge amount of work to make the en­vi­ron­ment a happy place for all the things upon which their own lives and our en­ter­prises de­pend. What sur­prised me, but ex­plains in­for­ma­tion I've heard be­fore, con­cerns clover. The bac­te­ria which live in its root nod­ules are fix­ing ni­tro­gen, as I think most peo­ple know, but it's not a one-way street. The clover feeds the bac­te­ria via ex­u­dates from its roots, a process which uses up to 20% of the energy the clover ob­tains from pho­to­syn­the­sis.

But when farm­ers put ni­tro­gen on clover, some­thing in­ter­est­ing hap­pens. The clover is quite happy and it doesn't bother to look af­ter its bac­te­rial helpers be­cause it doesn't need any­thing from them, so there's a drop in the amount of ni­tro­gen which is nat­u­rally fixed.

It's not just the ni­tro­gen-fix­ing bac­te­ria which form close as­so­ci­a­tions with plants. All plants pro­duce ex­u­dates which at­tract the sorts of bac­te­ria and fungi they need to help them ob­tain nu­tri­ents from the soil.

The rhi­zo­sphere, an area about 1-2mm thick around any root sur­face, is the re­gion in which most of this ac­tiv­ity oc­curs. The bac­te­ria which live in there con­stantly make nu­tri­ents avail­able to plant roots by di­rect ex­change, by ex­cret­ing waste prod­ucts and by dy­ing and de­com­pos­ing which re­leases the nu­tri­ents they hold in their bod­ies. Their pres­ence is also of­ten not ran­dom. Many plants form sym­bi­otic re­la­tion­ships with par­tic­u­lar fungi, the re­la­tion­ship named my­c­or­rhizae. My­c­or­rhizal fungi can live on the out­side or in­side a plants' roots. They are able to grow chains of cells out over ex­tra­or­di­nary dis­tances, ex­tend­ing into ar­eas plant roots can't reach, ac­cess­ing and trans­port­ing back many nu­tri­ents their host plants re­quire.

6even phys­i­cally trap ne­ma­todes and con­sume them!

For­tu­nately, when I was a new farmer I was de­ter­mined to ad­here to the prin­ci­ple that I would first do no harm, shy­ing away from chem­i­cally-ac­ti­vated fer­tilis­ers and from blan­ket spray­ing old pas­tures in favour of newly-sown species*, opt­ing in­stead to take the longer route of rais­ing fer­til­ity by the use of RPR (Re­ac­tive Phos­phate Rock) and lime.

My belief was that I would grad­u­ally en­hance the life and struc­ture of the soil by that method, cre­at­ing an im­proved en­vi­ron­ment for the plants I wanted to grow above ground.

If we pour some­thing nasty onto our soils or the plants above, we may make life un­com­fort­able or im­pos­si­ble for some part of the web of life in the soil and throw the whole thing out of bal­ance, some­times with long-term con­se­quences.

It would ap­pear that my vague sense of the world un­der­ground was cor­rect, but I did not pre­vi­ously un­der­stand how much plants con­trib­ute to the sys­tem, hav­ing pre­sumed they were sim­ply the ben­e­fi­cia­ries of a healthy soil. It turns out they're an in­te­gral part of a bal­anced ecosys­tem. How did I for­get those pri­mary school science pic­tures of trees, grass and worms in con­stant in­ter­ac­tion?

A pad­dock of two halves. This view looks down down the north­ern, 'bet­ter' half. The poorer-per­form­ing area is out of sight, to the right.

her­self and jumped that just fine. But we didn’t know there were some old rail­way irons ly­ing in the grass there. The end was pok­ing just past the edge of the bank. And she clipped it with her knee and fore­leg. It was a huge thump and I pulled her up straight away.

“The iron had gashed all the skin off her knee and then bumped down her shin, skin­ning that to the bone in two more places. She was still mov­ing fine. I don’t think it was hurt­ing her yet, so I just led her all the way back, bawl­ing my eyes out.” Maria smiled. “Yeah, I know about that!” “I stopped at my friend’s place, the boys with the mo­tor­bikes, and their dad sat me down and made me a cup of tea and just would not be rushed un­til I had got my­self to­gether. Mean­while, he had gath­ered dis­in­fec­tant and ban­dages and stuff.

“So we washed her gashes, just like you did, and I led her home re­ally qui­etly and my folks had the vet there by the time I got home. He stitched her up and ban­daged her and gave her an­tibi­otics.” “Did she heal up?” “Yes she did, but it took a lot of work, and boy, she hated those in­jec­tions. She never ever ac­cepted men in over­alls af­ter all the vet’s vis­its. Her knee ended up a bit lumpy, but it never trou­bled her or slowed her down. She was sound.

“Ac­tu­ally, it was good for us. Be­cause I had to wash and tend her ev­ery day, and get her to trust me, even if tak­ing the ban­dage off hurt. I did it as care­fully as pos­si­ble.

“I guess we learned from it all too. We both still loved to gal­lop around, but I made sure the way in front was safe. “What hap­pened to her in the end?” “Oh, we had lots of years to­gether. I sold her once when I first left home, but bought her back when I came north. She fi­nally died when she was 42.” “Wow.” “Yes, that’s quite old for a horse, and af­ter so long with her… well, I didn’t think another horse would ever re­place that sort of history and bond.” “Gee, I hope Sheba lives that long.” The Vet piped up at that point. “Well, it will take more than this mis­ad­ven­ture to stop her. Now, your job is to wash her leg ev­ery day, try to slough off any scabs to stop proud flesh de­vel­op­ing. And she is go­ing to need an­tibi­otics for a week or so, depend­ing on how it heals. No gal­lop­ing about for a cou­ple of months.

“Hope­fully you won’t be as silly as some peo­ple I know.”

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