Master-Class Improving Yields Reduced by Excess Water

     The first in a series of articles aimed at helping growers
     improve both crop and livestock nutrition by improving
     the productivity of the soil. 


     Improving yields that have been reduced by excess water

             Loss of nutrients to water  During each growing season, in certain agricultural cropping areas,
        rainfall can be heavy to excessive at times.   For many areas this can be especially true in the winter and 
        spring months.   Combined with high yields, extra water can have a very detrimental effect on soil fertility. 
        Growers with fields that have been heavily irrigated can experience the same type of problems. 
        
             In many fields too much water has caused some fertilizer nutrients needed for good crop production to be
        leached, or washed downward out of the topsoil.  This is especially true for nitrogen, sulfur and boron, as is 
        generally expected to be the case.   But under the right conditions, calcium is another element that can be lost
        due to high amounts of water.  As shown by soil tests, in order to avoid the loss of crop yields, more liming 
        needs to be done in many areas.  Yet in recent years less emphasis seems to have been given to the importance
        of liming than has been the case in the past.  

             The need for limestone to increase crop yields has become a significant factor in more and more fields.
        Some fields being checked for calcium losses on a continual basis have changed drastically within three or
        four years. Such changes are particularly expected on fields that do not have a history of good liming practices,
        and on fields that receive inordinate amounts of nitrogen or sulfur from whatever source.

             Watch that limestone!   But just applying some type of lime to correct the pH is not generally the best 
        answer.   In fact, some of the fields that have received high magnesium (dolomite) lime can still have an 
        adequate pH, and yet be limiting your crop yields.   This is because the levels of three other crop nutrients,
        in addition to magnesium, can greatly influence crop yield, and a need for them may not be properly reflected 
        by the pH.Calcium, potassium and sodium are the other elements in question.   If soils have too much
        magnesium (or too much of any one of the other three), the pH can appear to be okay or even too high, when
        in fact the soil does not have enough of one or more of the other three nutrients needed to produce at its best.

             You have to balance the nutrients   The only way to know what is actually the case is to have a detailed
        soil analysis run on the soils.   Such testing must measure the levels of each nutrient properly.    For those who
        are new to our soil fertility program the test procedure which we use provides these answers.  And from this 
        analysis it can be determined what lime, and how much, is needed from the various available sources.  Just
        putting on lime is definitely not the best route to take!   Too much high calcium lime (or calcium from other
        sources such as manure from laying hens, finely ground oyster shell, ground marl rock, and in some cases 
        gypsum, soft rock phosphate, or even compost) can tie up nutrients.   This includes potassium, phosphate,
        boron, iron, zinc, copper, magnesium and/or manganese.

             High-magnesium lime    Dolomite, or high-magnesium lime, can cause problems too.   When dolomite
        is applied in too large of a quantity it can cause an excess in magnesium and have a negative effect on yields. 
        The problem is it can be as long as three years after the excess lime has been applied before seeing the greatest 
        amount of potential damage to the crop yields. By this time, unless the grower has kept good records, a 
        connection between the liming and declining yields may be overlooked. (A moral here is to keep good records
        of when, where, how much and what type of lime each field receives.)  Have you applied dolomite lime on any
        of your fields in the last few years?  If so, count three crop years from the time of application and check the 
        yields that year and thereafter as compared to yields prior to liming.   Even if the applied magnesium from 
        dolomite lime will have a detrimental effect, do not expect to see that yields have dropped the first year.

             For example, when too much dolomite is applied to land for cotton, it can eventually cause the plant to
        send out two lesser roots instead of one longer taproot.   These roots do not go straight down, but curve to one
        side instead, and have less depth than the one taproot would normally have. (If you rip and hip, this effect will 
        not always be as evident.)  It will take three years to see the full negative effects of overusing dolomitic limestone.
        But when overused, once those effects have come into full effect it can cost a cotton farmer about ¾ bale of
        cotton per acre, every year, until the problem is corrected!

             Excess magnesium costs money    In corn, on medium to heavy soils, a high level of magnesium (15%+)
        costs the farmer 10 bushels of corn per acre.   Above 20% magnesium on the soil test reduces the yield by 
        another 5+ bushels per acre. In addition, it will require more nitrogen to produce each bushel of corn every year
        until the problem is corrected. In legumes, taking soybeans as an example, 13-14% magnesium levels can cause 
        10 bushels per acre loss per year, even when all other nutrients are present in the proper amounts.

             Be sure what your soil really needs    Even though too much, or the wrong type of lime can cut yields,
        limestone should always be applied where shown to be needed.   Applying the proper amount of lime in the 
        right form can provide far greater increases in yield than the losses that occur from misuse.    Have your yields 
        suffered in certain fields in the past few years?    If so, avoid the mistake of failing to correctly check for and
        properly apply any lime that is needed.  Just be sure that you use enough to correct the problem, but not so
        much that it causes problems three years from now and several years thereafter.   If there is a need for lime, 
        autumn is the best time to spread it for next Spring's crops.  Do it correctly as needed and see the difference
        liming can make for crops over the next several years.   

                                                                                Copyright    © Kinsey Agricultural Services, Inc. 2001. All rights reserved.