New Study of Potato Farming Methods at Loess Plateau

Even though it is such an important crop there, potato yields are lower than they could be.
The area has a dry climate with uneven precipitation.
Droughts are common, especially in the spring when crops are just starting to emerge.
If soil moisture was more reliable, the potato crops would do better.

Rong Li and colleagues at Ningxia University in Yinchuan, China set out to discover if different tilling and mulching practices could improve soil moisture -- and crop yields -- in the Loess Plateau.
The researchers studied three tillage options (conventional, no-till, and subsoiling) combined with three mulching options (no mulch, straw mulch, and plastic film).

Usually, the Loess Plateau fields are plowed, or tilled, after the harvest and left bare until spring planting.
This is known as conventional tillage.
Conservation tillage can mean not tilling the soil at all between crops (no-till).
Another conservation option is subsoiling: deeply breaking the soil with a long blade, without turning it.
Tillage helps water soak into the soil and improve water storage within the soil.

Li said, "We didn't know whether tillage with varied mulching practices would improve drought resistance during the potato seedling stage in these dryland farming areas."

The team studied the same field over two years -- a relatively dry year followed by a wet year.
For each combination of soil management options, they measured topsoil temperature, soil water content, seedling emergence rate, and marketable yield of potato tubers.

Plastic mulch warmed the soil more than the other mulching options.
Straw mulch had a cooling effect compared with no mulch.
However, all three options produced soil temperatures in the right range for rapid potato germination.
So it seemed that topsoil temperature was not the key factor for early seedling growth.

The team concluded that drought was the main factor limiting crop production.
Soil moisture during the seedling period is essential for crop success.
Techniques that maintained soil moisture improved both the emergence rate and strong seedling establishment.
Both are essential for good tuber formation and marketable yield.

Other findings include:
•Seedling emergence was lowest with conventional tillage and no mulch compared to other treatments.

•The highest emergence rates occurred when subsoiling was combined with plastic mulch.

•Within the same tillage option, seedlings in mulched plots were much taller than those without mulching.

•Straw mulched plots had the highest potato tuber yield, followed by plastic mulch.

•Conservation tillage (both no-till and subsoiling) with straw mulch led to higher potato yields and marketable tuber rates compared to other treatments.
•The highest marketable potato tuber yield was found in the combination of subsoiling with straw mulch. This yield was 14.9% higher compared to conventional tillage with no mulch.


Li and his team concluded that if the main goal is to increase soil moisture, straw mulch should be selected.
Straw is also relatively low-cost and environmentally friendly, while plastic mulch can cause pollution problems and is a less sustainable method.

"We recommend conservation tillage combined with straw mulch as a more favorable farming practice for drought resistance in potato seedlings," Li said. "This combination has great potential for greater crop production in our region and similar semi-arid dryland farming regions of the world."

In the Loess Plateau, where the potato is king, these findings may prove to be truly royal.

This work was supported by the National Natural Science Foundation of China.

I thought this was a pertinent report and wanted to make sure all here would have the opportunity to read it.

Redhawk

Is that report publicly available?  I don't have a good way to affect the huge potato farms in my area but if I figure it out, I can give them this.  We're sandy and moderately rainy but they still irrigate the hell out of the spuds.  Thanks for posting it Dr R.!

Mulching with straw
1) feed the soil minerals
2) humus holds more water + dissolved bioavailable minerals
3) encourage good non-parasitic soil life
4) increase water by cutting down on evaporation.
Things that no mulch and plastic mulch cannot do.

When it comes to subsoil "aeration" vs no till vs regular tillage. I am not too surprised in regular conditions.
But I have always wondered if maybe making the above catchment area more impervious will make my down hill "farmstead" have more water possible effectively doubling my rainfall amounts.

Redhawk,  Out of curiosity, the rotation for potatoes up here has been with small grains, usually barley or wheat.  At the same time that small grain acreage is being displaced by the soybean/corn juggernaut in recent decades, there is increasing interest in fall cover crops or fall-seeded covers for spring emergent green manure/mulch.  Do you think a fall seeded oat or rye crop could either become, or substitute for, the straw mulch for potatoes that is described in the Chinese research?  Thanks.....

hau Mike, as far as I know it is a 35 dollar fee for the full report, It was sent to me by a friend so I'll have to go looking for the best scientific site to get it from.

hau S Bengi, our "down Hill" is getting terraces with rock walls holding the soil in place.
The construction of these has come to a stand still this year because of other things taking up most of my "free" time.
What I liked most about this report is that it confirms most of the methods that work really well (loved the fact that plastic lost to straw mulch, I have been saying that for years).
As you know, the steeper the hill face the more important terraces become and I like to make mine as deep front to back as the hill will allow.
This makes my south slope interesting since some can be 3 feet depth and some can be 8 feet depth.
I only worry about that one measurement since there isn't a way to make them all uniform because of the terrain I live on.
For the most part at the valley floor I can make them 8 feet wide and as I work up the mountain side they will get skinnier and skinnier, then as the top gets near they can broaden out again to the 8 foot mark.

I set the walls so the water at the bottom of each terrace can drain into the next terrace below through small openings in the stacked wall construction.

Making such a system impervious will create an artificial water table, which may or may not become a hazardous situation, depending on location, steepness of slope, length of slope and what is at the bottom.
When we first started our earth works I used swale and berm only to end up with a blow out that washed out our road up the mountain side, lesson learned the hard way. Do not create and artificial spring where you don't want or need one to be.

Redhawk

hau John, yes I don't see any real problems arising from using a spring crop as the cover.
One of my customers does this with his winter wheat planting in his natural rotation, so you just won't be adding composting green material but every other year in a spring/ fall planting regimen.
I love the ideas of keeping growing things all year long, using one grow set as a chop and drop for the next rotation to be planted through that just cut mulch layer.
This has nutrients being replenished every  year, unlike that first example where he is growing for two seasons back to back before growing a chop and drop mulch crop.

With potatoes and small grains, the straw left from grain harvest could always become the mulch layer, or be turned into the soil as the potatoes are planted out.
Doing that would require some harvested straw held for covering the newly planted potatoes though.

Redhawk

Oooooh - I like this. Thank you for sharing!

This last year was the first year that I didn't use straw as mulch on my potato beds and our potatoes were smaller and tougher than in previous years. I usually save seed, but did a trial this year using saved seed potatoes, plugs from a big warehouse supplier, and store bought organic potatoes that I chitted.

I regulate water based on rainfall and temperature and found the only difference in yields in my saved seed beds from previous years was the absence of straw mulch on newly hilled potato beds.  I dig a small trench, lay the eyes, and cover, water, wait. When they are about 10 inches tall I hill them up really well so that only little bits are left over above the soil line. Then I wait a bit and let them grow. I put straw on them (a big 5-7 inch layer) when they are another 10-15 inches higher. Then water when the soil underneath the mulch is dry down to my knuckles (I just poke a finger down and if it's dry all the way to my palm knuckle, I water with a soup can out to measure. I've always overhead watered but next year I'm gonna use drip hoses and see how that works.)

The overall experiment found that the plugs from the big warehouse supplier actually produced more potatoes and bigger potatoes than my saved seed and store bought chitted potatoes. Go figure. (This result annoyed me, for various reasons. One of which being that I very much wanted the big box plugs to fail so I could experience a little schadenfreunde at the expense of giant corporations.)

I often try to stay away from long term straw mulch in the maritime NW as it just proliferates slugs and snails to an astonishing degree. This year, I'm growing potatoes out of the main garden in our pasture so that the ducks can take care of that slug/snail problem for me without trampling all my delicate starts. Nothing kills or eats potatoes in our neck of the woods. Even the slugs and snails hatch under the mulch in potato beds and then slime their way over to the radish and lettuce beds. Because they are buttfaces.

I'm in the MO Ozarks and have acidy, clayey loam. In late July and all of August, this clayey loam can turn into a solid, dry, hard mass that stops potato growth. I start my taters way before everyone else around here so they can be out of the ground in June. I get more, bigger and smoother taters than all my neighbors. My second closest neighbor finally gave up on them because he wasn't even getting a 2 to 1 return. My best has been about 5 to 1 and if things are ideal, you should be able to get 7 to 1. That is 7 lbs harvest for every 1 pound planted. If I did a better job of hilling, I'd be real close to that. My neighbors dig them in mid-late July and let the soil totally dry out before harvesting for some reason. Takes them half a day digging a few rows. I dig mine whenever the soil is ideal for any sort of digging. One year, I was able to just pull up the plants with taters attached but I don't have that good a tilth now. Need to work on that. I collect oak leaves and pile them up so they can break down. I add that to my tater beds for fluffiness. Doesn't seem to steal too much nitrogen since they're half broken down already.

I plan to try a second crop in the fall but haven't yet. I'll be putting up a high tunnel this year and will probably do my fall taters in it or at least some. If it's well drained enough, they can be left in the ground and dug as needed. I've found some in the ground the following Spring that were still good. One of these years I'll have a root cellar.

Lindsey Jane wrote:...... and then slime their way over to the radish and lettuce beds. Because they are buttfaces.

Quick  amusing story:  When we lived in the Willamette Valley of Oregon, ths slugs were having a field day clobbering the garden of we, the newbies to the PNW.  Then we learned the trick of placing a submerged tin can into the ground that contained sugar and yeast....supposedly the alcohol and ferment attracted the slugs and they were to fall into the can and drown.  Anyways, the fermentation did in fact occur......but was discovered more quickly by our pot-bellied pig than the slugs!  She drank the contents  of a all cans and became the proverbial 'mean drunk' for the next several hours.   She did sleep like a baby for many hours thereafter, but we needed to change our slug deterrent approaches.... :-/

Seed potatoes:  I'm wondering if you possibly are having similar problems to what I think I ran into with my seed potatoes.  Even though small potatoes used as seed *can* go on to produce plants that yield large potatoes, if the seed that is used year after year is always what remains in the root cellar.....i.e., the ones that were avoided because they were too small for meals during the winter......this can end up shifting the genetic constitution of your population to small-tuber potatoes.  Since we have been saving and reusing the same seed stocks for over 15 years, I think I started to see the results of always using the small potatoes as seed.  Since I was not careful to save potatoes from specifically high-yielding plants, I suspect my genetic stock is now highly skewed towards small-producing plants.  This was partially validated by what you just described....using seed stocks in the 2018 growing season that came from several different sources and noting the paltry output and size of my previously-saved seed stock compared to the new stock.  But I like the mulching and crop nurturing that you describe to help the crop out the best way possible.