Economic and Agronomic Impacts of Varied Philosophies of Soil Testing¹

Abstract

Philosophical differences exist in the interpretation and recommendations made from soil test values acquired by different organizations that provide advice to farmers on fertilizer use. It was the objective of this study to evaluate the economic and agronomic impacts of these varied philosophies with particular reference to concepts of cation ratio, nutrient maintenance, and nutrient sufficiency level. Field experiments were conducted during 1973–1980 on four major soils of Nebraska comparing yields of corn (Zea mays L.) grown with fertilizer treatments as recommended by five soil testing laboratories operating in the state. The 29 field comparisons revealed no real yield differences despite wide variation in number, rate, and cost of nutrients applied. Since soil test levels are increasing or at least holding steady with the “nutrient sufficiency” approach to soil testing, we find no economic or agronomic basis for the “balance” or “maintenance” concepts on these representative soils of the western Corn Belt. Not to be overlooked are environmental implications nor the waste of energy and resources from any approach responsible for excessive fertilizer use. It is recognized that reserves of available nutrients in the deep subsoils and underlying soil‐forming materials in this region have a substantial bearing on soil test calibration and that different calibrations may exist with less favorable subsoil rooting conditions.

The potassium paradox: Implications for soil fertility, crop production and human health

“…Many leguminous crops are sensitive to Cl − toxicity, including soybean 120,131 and alfalfa 159,160,198 , and Cl − can reduce soil N availability by inhibiting nitrification in soils 195,196,199,200 (see also supplementary references [53][54][55] for the online version of the paper) and by acting as a competitive anion that suppresses plant uptake of NO 3 − 147,201,202 (see also supplementary references [38] and [56][57][58][59] for the online version of the paper). A further difficulty arises from the mobility of Cl − in soils, which intensifies profile leaching of Ca 2 + as a counterion [203][204][205] .…”

The calcium requirements of pastures in New Zealand: A review

“…This could mean that requirements for Ca are overestimated if CEC is used as the basis for fertiliser recommendations. This is possibly one reason why fertiliser recommendations based on the base saturation ratio philosophy overestimate some nutrient inputs for no extra gain in productivity (Olson et al 1982).…”

Agricultural chemicals in ground water: Extent and implications

“…Such losses were "built-in" to N-fertilizer yield-response models before we began to understand the inefficiencies and losses involved. This is also evident from studies noting the wide variance in N-fertilizer recommendations (and costs) which have not resulted in significant yield differences (e.g., Olson, 1985;Olson et al, 1982).…”