@misc{orgprints392,
          number = {19},
           title = {Exchangeable potassium and potassium balances in organic crop rotations on a coarse sand},
          author = {Margrethe Askegaard and J\orgen Eriksen and J\orgen E. Olesen},
            year = {2003},
           pages = {96--113},
         journal = {Soil Use and Management},
        keywords = {Exchangeable potassium, potassium leaching, potassium balance, organic farming},
             url = {http://orgprints.org/392/},
        abstract = {Crops on sandy soils (<5% clay) are exposed to K deficiency due to the small release and high leaching losses of K. Reliable tools are needed to improve the K management in cropping systems with limited K input, such as organic farming where import of nutrients are restricted according to the EC regulations. We investigated K balances and exchangeable K (Kexch) changes in an organic crop rotation experiment. Potassium leaching decreased from 42 kg ha-1 in 1998/99 to 21 kg ha-1 in 2000/01 as an average of a crop rotation (spring barley, grass-clover, winter wheat and pea/barley) with manure application and without catch crops. In the same period, spring Kexch decreased from 5.0 to 3.0 mg K 100 g-1 soil (0-20 cm). The retention of the straw K left in the field after harvest increased with decreasing levels of Kexch. The cereal crops did not respond to K application but in the pea/barley mixture the pea yield increased by 46%. The concordance between measured K balances and changes in Kexch was weak. Exchangeable K is suitable as a tool for K management on a crop rotational basis, and a Kexch above 3 mg 100 g-1 soil in the autumn should be avoided to minimize K leaching.}
}