AbstractTo study the influence of potassium (K) fertilizer rate on soil test K values, crop yield, and K‐leaching in sandy soils, four long‐term fertilizer experiments (0–60–120–180 kg K ha−1a−1) were initiated in 1988 in northern Germany on farmers fields. Clay content of the plow layer was about 4, and organic matter between 2 and 5. Plant available soil K was estimated with the double lactate (DL) method.Small grain cereals (rye and barley) did not respond to K fertilization in the 7‐year period even though the soil test value of the K‐0 plots decreased from ca. 90 to ca. 30 mg KDLkg−1within 3 years. This value remained almost constant thereafter. Crop removal (including straw) of 75 kg K ha−1a−1was therefore apparently supplied from nonexchangeable K fractions. Compared to the optimum, no K application reduced the yield of potato by up to 21, and that of white sugar yield up to 10. Maximum potato yield was obtained by annually applying 60 kg K ha−1which resulted in a test value of 60 mg KDLkg−1soil. Maximum potato yield was also obtained at 40 mg KDLkg−1soil, however, with a single application of 200 kg K ha−1. Similar results were obtained with sugar beet. This indicates that for maximum yield, even for K demanding crops, it is not necessary to maintain KDLvalues above 40 mg K kg−1soil throughout the entire crop rotation.Soil test values increased roughly proportional to the K fertilizer level. About 120 kg fertilizer K ha−1a−1, markedly more than crop K removal, was required to maintain the initial KDLof 90 mg kg−1. The K concentration of the soil solution in the top soil measured after harvest was increased exponentially by K fertilizer level and so was K leaching from the plow layer into the rooted subsoil. The leached quantity increased from 22 kg K ha−1a−1in the plot without K application to 42.79 and 133 kg Kha−1a−1in plots supplied with 60, 120 and 180 kg K ha−1a−1respectively. Soil test values around 100 mg KDLkg−1on sandy soils, as often found in the plow layer of farmers fields, lead to K leaching below the root zone that may exceed the crit
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机译：摘要为研究钾肥施用量对沙质土壤试验钾值、作物产量和钾淋用的影响，于1988年在德国北部开展了4次长期施肥试验（0-60-120-180 kg K ha−1a−1）。犁层的粘土含量在4%左右，有机质在2%-5%之间。采用酸（DL）法估算植物有效土壤钾。小粒谷物（黑麦和大麦）在7 a期间对钾施肥无反应，尽管K-0样地的土壤试验值在3年内从约90 mg KDLkg−1降低到约30 mg。此后，该值几乎保持不变。因此，75 kg K ha−1a−1的作物去除量（包括秸秆）显然是由不可交换的钾馏分提供的。与最佳施用相比，不施钾可使马铃薯产量降低21%，白糖产量降低10%。通过每年施用60 kg K ha−1获得最大马铃薯产量，其测试值为60 mg KDLkg−1土壤。然而，在40 mg KDLkg−1土壤下，单次施用200 kg K ha−1，也获得了最大的马铃薯产量。甜菜也获得了类似的结果。这表明，为了获得最大产量，即使对于要求钾的作物，也没有必要在整个作物轮作过程中将KDL值保持在40 mg K kg−1土壤以上。土壤测试值的增加与钾肥水平大致成正比。需要约120公斤肥料K ha−1a−1，明显多于作物去除钾量，以维持90 mg kg−1的初始KDL量。收获后测得的表层土壤中土壤溶液的钾浓度随着钾肥水平的增加而呈指数增加，从犁层到根系底土中的钾浸出量也呈指数级增加。浸出量从未施用钾的地块中的22 kg K ha−1a−1增加到60、120和180 kg K ha−1a−1的地块中的42.79和133 kg Kha−1a−1。在沙质土壤上，土壤测试值约为 100 mg KDLkg−1，这在农田的犁层中很常见，导致根区以下的钾浸出可能超过暴击
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