Andrew McGuire

Can manure sustain soils?

Posted by Andrew McGuire | September 19, 2017

Once you start asking questions, innocence is gone. -Mary Astor

How much manure do you need to spread to maintain your soil’s organic matter? Photo: werktuigendagen via Wikimedia Commons

My first question about manure, “Can Manure Supply Nitrogen and Phosphorus to Agriculture?” was answered here. But manure is more than nutrients. The bulk of manure is organic material, the carbon that the primary-producer feed crop took from the air and built into organic molecules (hence the name “organic”). When added to the soil, some of this manure bulk ends up as soil organic matter.

Organic matter is a small but crucial portion of soil. If we can maintain a soil’s organic matter levels, we have gone a long way in maintaining soil health and function. Can manure do this? Can manure sustain soils?
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Can Manure Supply Nitrogen and Phosphorus to Agriculture?

Posted by Andrew McGuire | September 7, 2017

Once you start asking questions, innocence is gone. -Mary Astor

Manure, whether fresh, old, or composted, is often declared a key component of sustainable agriculture. From countless trials, researchers have come to similar conclusions (Haynes and Naidu 1998). Manure use is promoted as a solution in discussions of sustainable agriculture topics including: soil fertility, soil health, organic farmingregenerative farming, carbon sequestration, and renewable resources. However, I have questions. Not about the actual spreading of manure, or calculating application rates, but about manure’s role in sustaining agriculture. Is manure a sustainable source of nutrients? Is manure a sustainable organic soil amendment, able to build soil organic matter, store carbon in the soil, and so assist in reducing greenhouse gases? When is manure application a sustainable practice?

In my next few posts, I will answer these questions with the hope of putting manure in its proper role in sustaining agriculture. First, let’s look at the nutrient-supplying potential of manure. It all starts with figuring out where manure comes from. Read more »

Cover crop best bet is monoculture, not mix

Posted by Andrew McGuire | December 21, 2016
Can you see 17 species in this cover crop mix? Photo: A. McGuire.

Can you see 17 species in this cover crop mix? Photo: A. McGuire.

Cover crops are great. If I thought I could get away with it, I would just grow cover crops in my garden. They protect the soil, feed microbes, build soil structure, add root channels, and support beneficial insects. I think they look cool too. When cover crop mixtures got popular a few years ago, I got excited and grew a 17 species mix. It looked really cool, I mean, diverse, with all sorts of seeds that became all sorts of plants.  I took pictures, showed my kids, and even had a neighborhood open garden event! (Well, maybe not that last one) Then I grew some vegetables after the cover crop. They did OK. Just OK. I wanted it to be the best tomato/squash/cucumber/lettuce crop ever, but I could not tell the difference between these vegetables and those I had grown after many previous un-biodiverse cover crops. Recent research results may explain this. Read more »

Comparing effects of herbicides, fertilizers, and tillage on the soil

Posted by Andrew McGuire | December 8, 2016
Is this better than an herbicide for the soil? Photo: United Soybean Board.

Is this better than an herbicide for the soil? Photo: United Soybean Board.

In a past post, I argued for the use of an herbicide instead of tillage to kill a soil-building cover crop. My post was mostly observation of the damage of tillage on the soil as compared to the lack of damage, at least visually, from the herbicide. But others suggested that herbicides may not be as benign in the soil as I portrayed them. Here is the latest science on the topic.

A series of reviews have been published on the effects of herbicides on the soil, starting with Bunemann et al. in 2006. They concluded, “The herbicides generally had no major effects on soil organisms.” More recently, a review by Rose et al. (2016) found, “Overall, the majority of papers reported negligible impacts of herbicides on soil microbial communities and beneficial soil functions when applied at recommended field-application rates.” Read more »

Crop rotation: In praise of deliberate, sequenced disruption of natural systems

Posted by Andrew McGuire | December 1, 2016

For years, researchers have been looking to polycultures, biodiversity in space, as a way to improve agriculture (Trenbath 1974; Tilman et al. 1997; Cardinale et al. 2011; Finney and Kaye 2016). Behind this research is the idea that nature is the best model for agriculture. Because we find that nature is generally a polyculture, we should mimic this biodiversity on the farm. Natural is now viewed as the best option. Today, however, I want to commend a most unnatural practice, crop rotation.

The unnatural, disruptive transition of wheat monoculture to bean monoculture – good for agriculture

The unnatural, disruptive transition of wheat monoculture to bean monoculture – good for agriculture

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Filed under Sustainable Practices and Technology
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The New Urban Indoor Industrial Agriculture… but Why?

Posted by Andrew McGuire | November 16, 2016
Vertical farm crop wall demonstration project. Where is the soil? Photo: State Dept. via Flickr cc

Vertical farm crop wall demonstration project. Where is the soil?
Photo: State Dept. via Flickr cc

There is a new style of urban agriculture appearing around the world. The efforts differ in details, but they all use buildings or structures not originally designed to grow plants – no greenhouses. Carried out in old shipping containers, warehouses, and high-rises, perhaps even in an old factory or two, these “farms” bring agriculture fully indoors. Without sunshine, these farms rely on artificial lights shining on plants 24 hours a day in some cases. Without soil, plants sit in plastic pipes, or float on polystyrene rafts, stacked in tiers.  Without rain, nutrient enhanced water is cycled to the plant roots through piping, pumps and filters. Without wind, fans provide ventilation, ducts and vents deliver heated or cooled air for year-round production.

All this requires energy. These farms are plugged in, reliant on outside power. Outdoor farm fields are off the grid, at least for the production portion of the food chain. Even a continuous corn crop, the scorned example of “industrial” agriculture, is not affected by a blackout. While an outdoor “industrial” crop is still subject to the biological realities of crop growth cycles and seasons, crop production in these indoor farms can be sped up and streamlined. All it takes is lots pipes and tanks, cables and lights. Read more »

The Fallout of October Rains in the Desert

Posted by Andrew McGuire | November 1, 2016
Photo: C. Chene via Flickr cc.

Photo: C. Chene via Flickr cc.

Here in the Columbia Basin, something extraordinary has happened; it rained a lot in October. Although not technically a desert, we are normally desert-like from June-October. Not this year. How much rain did we get? Well, in Ephrata where I live, we have seen over 2.5 inches of rain. I know, not much, even by Inland Northwest standards. But 2.5” is record rainfall for us – never have we seen so much rain in October – and it has had some consequences.

They don’t often admit it, perhaps out of respect for dryland farmers to the East, but farmers in the Columbia Basin prefer to get their water out the end of a sprinkler. They like to control how much and when the water falls on their fields.  When it comes out of the sky, it messes things up. The rains have delayed harvest of late potatoes, onions, dry beans and other crops. Although I expect all these crops will be harvested, the wet ground and crops probably caused some yield losses, and equipment traffic on wet soils likely compacted soils which will require additional tillage to fix.

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Filed under Climate Change, Sustainability
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Defending the Proper Use of Monoculture

Posted by Andrew McGuire | September 27, 2016
Monoculture of dry edible beans. Photo: A. McGuire.

Monoculture of dry edible beans. Photo: A. McGuire.

Many bloggers have it wrong, Wikipedia had it wrong, and when I found that Agronomy Journal got it wrong, I was compelled to write on the topic once again. Monoculture is not the year-after-year production of the same crop in the same field. That is mono-cropping or continuous cropping, where the better alternative is crop rotation. Monoculture is “when only one crop species is grown in a field at a time” (Loomis and Connor, 1992), and the hard-to-manage alternative is polyculture or intercropping. You can take a picture of monoculture, but not of mono-cropping.

Just where this widespread misuse of “monoculture” started, I am not sure. It probably precedes the internet, and may have something to do with the similarity of monoculture and mono-cropping. More recently, Wikipedia played a part. For years it had a definition that combined the meanings of monoculture and mono-cropping. I suspect that this incorrect definition, and the fact that many people without agricultural backgrounds write about agriculture, has led to the widespread misuse we see today. Read more »

Filed under Sustainable Practices and Technology
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The Benefits of Combining Organic and Synthetic Nitrogen Sources

Posted by Andrew McGuire | June 26, 2016

Dan Sullivan, OSU soil scientist, caught my attention during his presentation at the 2014 Building Soils for Better Crops workshop. Speaking about organic amendments and how to use them for both building soils and for nutrient supply to crops, Sullivan suggested that low nutrient organic amendments, like compost or composted manures, be used in combination with synthetic nitrogen fertilizers. This combo, he said, has benefits over the use of either by itself.

Wheat could benefit from a combination of organic and synthetic nitrogen sources. Photo: USDA ARS

Wheat could benefit from a combination of organic and synthetic nitrogen sources. Photo: USDA ARS

The decomposition that produces compost reduces its nutrient content and stabilizes it. Because it has decomposed some, more of it will end up as soil organic matter than with fresh organic materials. When compost is applied to a field, it will continue to decompose slowly – faster as the soil warms up – releasing a slow stream of nitrogen into the soil solution.  If the compost is being used as a nitrogen source, this flow of nitrogen often cannot keep up with crop demand. One option is to use organic materials with higher amounts of available nitrogen, but these are very expensive; I found a liquid hydrolyzed fish product that could be applied through irrigation water, but it cost $17.76 per pound of nitrogen, over 20 times the price of synthetic fertilizer nitrogen. At this price, these materials make economic sense only for very high value organic crops. This is most likely why organic wheat, a lower value crop than organic vegetables or fruit, produces less grain with lower protein content than wheat produced with synthetic nitrogen fertilizers (Seufert et al., 2012).

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Organic Farming Provides Ecosystem Service and Solves Weed Problems

Posted by Andrew McGuire | April 14, 2016

In nearly all surveys of organic farmers their top priority for research is weed control. Weeds are a tough problem to solve, but with creativity and spunk, researchers in Spain have done it! In their 2016 paper, “Arable Weed Decline in Northeast Spain: Does Organic Farming Recover Functional Biodiversity?” Chamorro et al. provide a unique glimpse into the sort of thinking it will take to move agriculture to a different place. In a series of unanticipated turns, the authors lead us down a path to weed-free agriculture.

First, they contend that weeds are misunderstood. Weeds, as the paper admits, are a bane of agriculture, reducing yields as they do, but in a subtle departure, we are then told “The role of weeds in agroecosystems has been largely debated.” From this debate, the authors conclude that “the role of weeds is manifold”; weeds are not just yield-robbing competitors of crops, they also provide an “ecosystem service.” Read more »

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Contact Andrew McGuire

Email: andrew.mcguire@wsu.edu