Dear Portia,

I agree to a large extent with John and only want to add a few things here,

First of all it is better not to use averages, because it hides spatial variation in soils. Just like John, I suspect that because of high Mg and Na, depending also on soil texture, these soils will show surface sealing and a compacted subsoil. This, in part, can indeed be remediated by applying gypsum. But it also depends of how much S is already present in the soil, since gypsum contains both Ca and S. Even on acid soil Gypsum generally does not increase pH.

With respect to plant nutrition not only Ca is deficient, but also K. Applying Ca (as Gypsum) and K will have the dual advantage of improving plant nutrition and soil structure. A better soil structure is likely to increase moisture infiltration, rooting depth and to decrease soil erodibility. Also for K amendments you have to look into what more elements the fertilizer contains and relate that to the total soil chemical constellation.

Your observation on the relation between soil Ca content  and pH is a clear confirmation that the relation usually assumed is a preconceived concept.

You will find a paper on these issues in Geoderma 121 (2004) pp.65-82.

Another paper on related issues is given below.

Kind regards,

Roelf L. Voortman

http://vfrc.org/getdoc/a88fc6c3-27c1-443a-85e2-40eff0450892/VFRC_Report_2015-1.aspx

Though your soils are not sodic,they are behaving like saline_ sodic soils,having pH less than 8.5 but exchangeable sodium greater than 15%.There is a need to analyze water soluble salts in the samples. Addition of amendment like gypsum and leaching of salts from the soil is important. But in the absence of sufficient water availability, only possibility which appears to me is application of well decomposed manure in small amounts,4-5 tons every year or 15-20 tons once in 4-5 years.Manure also to be applied in rainy season to facilitate interaction with soil and amelioration.

To decrease salinity in your soil without leaching, try to extract salt from soil by phytoremediation. You can use Quinoa crop (6 months of crop cycle) as it's very adapted to arid conditions, and the grains are very rich in proteins. The crop gather salt from soil and store them in their leaves, take of the grains and recycle the leaves somewhere else.

Good luck

Khalid AZIM

@ Rao, luckily we have access to a lot of manure,  these samples were taken in a dry-land dairy farm, we just need to figure out the logistics of when we can start manure application. 

@ Khalid, I am not familiar with the process of phytoremediation, I have however done some research onto the topic and I find its quite an interesting approach and feasible solution to our problem.  

Thank you both for your insights, I believe the information you have provided will help a lot.

Application of organic manure is a promising approach to address the problem you mentioned, but the application method is also of great importance. Based on our field practices, I strongly recommend you to firstly braodcast them and the bury them to the soil depth of 10-20cm by ploughing or furrows.

Second question, many factors are related to soil acidity, and in your case, base cations play important role in soil pH. Cretainly not only Ca, but Mg, K, Na. Their binding forms also impact the soil pH, such as carbonate or sulfate. You could look through some archived papers, e.g., "Acid and Alkali Buffer Capacity of Typical Fluvor-Aquic Soil in Huang-Huai-Hai Plain". The soil tested in that paper was similar to your current.

Good luck!

Ping

Please find attached these two papers.

@Ping, thanks very much, the paper that you recommended I read, could you send it to me please?

@Khalid, thanks for the papers, I am finding, there is still quite a lot that I need to familiarize myself with this process/method you mentioned. I am however concerned a bit, the crops that have been used to extract the salts, would they be palatable to cows or sheep? I am asking this because , some dairy farmers  especially here in South Africa do not see the financial value in growing something that wont be of use to them e.g feed the proposed crop to their dairy animals, even though I as a researcher see the value. It is the unfortunate truth, that is why the concept of sustainable farming hasn't been fully adopted by some farmers this side. 

@ Shawn, I feel I need to mention this, I first had to ask google what "dovetail" means before I could fully understand your response...lol. Nevertheless, thank you for your response. In the case where constant water supply is not available, would lime a lone and rainfall water give similar results? And which lime? gypsum or dolomitic?

Well, quinoa crop is very known as an alternative to wheat. Please find attached a technical note and a summary of research experiment done in southwestern of Morocco in a framework of a PhD student (Dr. Abdelaziz Hirich a friend of mine). You can get more info to convince farmers to shift to this valuable crop.

Barley is another phytoremediation option.  It is of note that the focus so far has mainly been attempting to change the sodium and magnesium levels in the soil. Using phytoremediation is a long slow process  taking several seasons before any great progress is made. The ideal would be to choose tolerant perennial pasture species and match the livestock breed & species to the expected feed quality. The question on why the high pH? This is easily understood when the data is converted to Base Saturation values. To do this you will also need the potassium values.

One can opt for phytoremediation if the remediating crop can meet the fodder/feed requirements of dairy animals. Lime(calcium carbonate) is applied to acid soils as amendment while gypsum is applied to sodic/saline_sodic soil. Farmyard manure is applied (ploughed in  or incorporated) in both acid and sodic soils as amendment. It can also partly meets the nutrient requirements of forage crop.Amount of manure application may in small amounts or up to 15-20 tons /ha preferably in rainy season.

Hi Portia,

Lime won't work in these soils since it will only go into a soil solution when the pH is below about 5.5. Your soils have a high level of  magnesium and sodium cations. While sodium is well known to cause dispersion (sodic soils), high levels of magnesium can also cause this, so your high Mg levels will likely also be contributing to a dispersive soil.  Both Na and Mg can be remediated by displacing them with calcium using gypsum (calcium sulphate). I am assuming that your soil is dispersive. I have included a link to a simple field test you can do to determine how dispersive your soil is.

I'm not sure why you are suggesting that some of these cations can affect pH? It is really the other way around - high and low pH values can affect the solubility of these cations. Your pH appears to be in an ideal range (ph7 is neutral so your pH values are neither acid nor alkaline) so would not be limiting any of the cations you listed. 

To better answer your question, it would be good to know the productivity goals of the pasture you are talking about. Is this high input/high production or is it more marginal? What is the rainfall in your area? What pasture species are you growing or do you want to grow?

Kind Regards,

John

http://www.dpi.nsw.gov.au/__data/assets/pdf_file/0008/127277/Slaking-and-dispersion.pdf

Hi John

The rainfall varies from approximately 700 mm to 1250 mm throughout the year. The predominant type of pasture grown is kikuyu in summer and rye-grass in winter season over an average area of 600ha. I would say its both high input and high productivity farm which carries on average, 1200 sheep and 1000 cows in milk.

Thanks!

Dear Portia,

I agree to a large extent with John and only want to add a few things here,

First of all it is better not to use averages, because it hides spatial variation in soils. Just like John, I suspect that because of high Mg and Na, depending also on soil texture, these soils will show surface sealing and a compacted subsoil. This, in part, can indeed be remediated by applying gypsum. But it also depends of how much S is already present in the soil, since gypsum contains both Ca and S. Even on acid soil Gypsum generally does not increase pH.

With respect to plant nutrition not only Ca is deficient, but also K. Applying Ca (as Gypsum) and K will have the dual advantage of improving plant nutrition and soil structure. A better soil structure is likely to increase moisture infiltration, rooting depth and to decrease soil erodibility. Also for K amendments you have to look into what more elements the fertilizer contains and relate that to the total soil chemical constellation.

Your observation on the relation between soil Ca content  and pH is a clear confirmation that the relation usually assumed is a preconceived concept.

You will find a paper on these issues in Geoderma 121 (2004) pp.65-82.

Another paper on related issues is given below.

Kind regards,

Roelf L. Voortman

http://vfrc.org/getdoc/a88fc6c3-27c1-443a-85e2-40eff0450892/VFRC_Report_2015-1.aspx

Hi Portia,

We come the issue of how you can theoretically fix it versus how you can practically and economically fix it. 600ha is a large area to be applying 2.5-5 tonnes/ha of gypsum!  Roelf has some great points - in regards to the spatial variation, it might be good to look at the variation in the paddock as well as the test results - are there areas which are unproductive and waterlogged?  It would be worth running a few test strips of gypsum out to see if you are getting a response. 

I have attached a section of a soil management manual I co-authored a long time ago - chapter E4 deals with sodicity. I have also attached an article on managing kikuyu pastures by others far more knowledgeable than me on the subject.

Good Luck!

http://www.dpi.nsw.gov.au/__data/assets/pdf_file/0004/167386/soilpak-dcw-Part-E.pdf

http://www.dpi.nsw.gov.au/__data/assets/pdf_file/0012/359949/Milk-production-from-kikuyu-grass-based-pastures.pdf

Soil saturation extract analysis can provide the amount of soluble bicarbonate and carbonate ions,which cause the rise in pH. In soils with high pH or in high Mg ions in solution and on exchange complex, dispersion of clay colloids is common,which will block micro pores of soils and thus would  cause reduction of water filtration. Soils area with annual rainfall of 700 mm  such predicament is common.

Late in the day, but I feel the need to correct the statement that 'lime won't work on these soils'.  In Australia lime application with gypsum increases the duration of the beneficial structural effect on soils of high clay content even when the pH is neutral.

G'day Portia, Looks like you already have plenty of good advice. We have used gypsum successfully in a sodic soil that sounds similar to yours. It seemed to address both the compaction and the high Na in our expts - see Crop and Pasture Science (2014) vol 65, 922. Cheers and good luck, Wal Anderson.

http://landresources.montana.edu/nm/documents/NM4.pdf

http://landresources.montana.edu/nm/documents/NM4.pdf

As it is a dairy farm and abundant manure is available it desired to  plough in or incorporate sufficient manure in soil not only for amelioration but  also to provide nutrition to   two grasses grown in rotation. This may not involve much cost like gypsum and also water limitation for draining the soil may not be a problem in case of manure.

gypsum apliccation - 50 x % of clay = x kg/ha

Dear friend, you can try the Karnal Grass which can be grown on high pH in highly alkali conditions.

Thanks

Dear Portia

Based on the basic cations which are present in your soils, i would say your soil is having normal pH only (6.5 to 7.5). With respect to pH increase, all most all the basic cations are responsible for increasing the pH of the soil. As per your data, the order of cations presence in your soil like Ca>Mg>Na>K. This particular soil is suitable for all the grasses. If you have any specific problem with respect to pasture or grass cultivation kindly inform