Soil Testing 



asa 



Management Tool 



Oh no! Not another boring article on soil testing. 

 Maybe yes, and maybe no. Hopefully, this article 

 will inform you as to all the fascinating things going on in 

 the soil-testing world, especially in New Hampshire and 

 New England. As we move towards using more and more 

 "residual waste" products (wood ashes, sludge, compost), 

 environmental monitoring through soil testing takes on 

 increased importance. If we don't use the best procedures 

 and labs, the variability of the results may interfere with any 

 conclusions made. 



It's a little known fact that for the last 8 or 9 years a small 

 group has been working on updating and improving the soil 

 testing lab at UNH. We can confidently say that our lab now 

 leads most universities in New England in the accuracy and 

 reliability of soil test results and recommendations. What 

 we've been doing is basically sharpening our soil testing 

 tools, so that they will be more effective and efficient when 

 we use thera 



There have been several areas where improvement has 

 been made, some in the lab and some in the field. Although 

 much of the field work has been done in forage crops, some 

 of the information can be transferred (applied) to other 

 crops as well. Finding out how to effectively maintan or 

 improve soil fertility and health, we can make it a better 

 place for all plants. 



The major new area has been in use of soil nitrate testing 

 to predict niti-ogen fertilizer recommendations. Most of the 

 field work is being done with field com since com is a major 

 nitrogen user. However, more is now going on to utilize this 

 test on sweet com and other vegetables. Unlike some of our 

 other tools, this one cuts two ways. With respect to the 

 environment, it allows us to reduce the risk of water 

 contamination fi-om nitrates. From the profitability stand- 

 point, it allows us to reduce the cost of producing a good 

 crop. 



Much of the field work involves the use of periodic soil 

 sampling, both prior to and after fertilizer ^plication. By 

 monitoring nutrient levels throughout the season, we can 

 begin to develop recommendations based on scientific 

 findings. One of the most compounding factors is soil type. 

 Since soil characteristics vary with soil type, we needed to 

 first group soils wth similar properties, and then work with 

 soils in each of these groups. Another challenge is to 

 evaluate the soO at various stages of the rotational scheme, 

 since the nutrients (especially Nitrogen) supplied to plants 

 varies with the crop history and sequence. Sound compli- 

 cated? It's really not, compared to some of the other fertility 

 research going on in New Hampshire, but it does take time 

 to develop information. 



TomBuob 



An example of this type of field work was demonsti^ed 

 on five sites this past summer. Farm fields are used rather 

 than the greenhouse so that tiie results will represent what 

 goes on under natural conditions. Once the sites are identi- 

 fied, soil samples are taken to determine what type and how 

 much of a supplemental fertilizer (other than nitrogen) is 

 needed to grow the crop. After the crop is planted and 

 begins to grow, soil nitrate samples (12-inch core) are taken 

 at various intervals to evaluate the nitrogen supply for the 

 crop. Normally, under production conditions, the nitrogen 

 recommendation is based on a sample taken when the com 

 plant is between 8 and 12 inches. This has been found to be 

 a good time to evaluate the niti-ogen supply which will be 

 available to the plant throughout the season, and also allows 

 sufficient time to apply any additional fertilizer which might 

 be needed. Since the time of maximum uptake of nitrogen is 

 when the com plant is between 2 feet and tasseling, this also 

 reduces the risk of fertilizer losses to the environment 



In our test plots, we continue to soil niti-ate sample 

 throughout the remainder of the season to try to determine 

 the fate of the applied niti-ogen. Since there is soil niti-ate 

 from the fertilizer as well as from decaying organic matter in 

 the soil, some plots do not receive any fertilizer. In this way 

 we can approximate how much of the nitrogen is coming 

 direcfly from the soil. At harvest, yields are harvested on all 

 the plots to determine if there is any difference due to the 

 various levels of fertilizer. 



In this case, tiiis was the first time that com was grown in 

 the field for several years. For this reason there was very 

 little increase in yield after 50 pounds of nitrogen was added. 

 This is because nitrogen for Uie decaying sod was able to 

 supply most of it Since this was actually a poor sod, extra 

 fertilizer was needed. When a well-fertilized sod is used in 

 rotation wth com, very little, if any, additional fertilizer is 

 needed. Since the soil nitrate test can help us evaluate these 

 nitrogen sources, we can reduce the cost of growing the 

 crop as well as protect the environment from the loss of 

 excess niti-ogen. 



As we continue to shaipen this tool and use it and otiiers 

 to grow our crops, we can continue to improve production as 

 well as protect our environment If agriculture is to remain 

 vibrant, this is a necessity. * 



Tom Buob is Extension Educator, UNH Cooperative Exten- 

 sion, Grafton County. His address is North Haverhill 

 County Court House, PO Box 191, Woodsville, NH 03785. 

 He can be reached by calling (603) 787-6944. 



February 6? March 1993 

 31 



