Macronutrient-Use Efficiency and Changes in Chemical Properties of an Oxisol as Influenced by Phosphorus Fertilization and Tropical Cover Crops

Cover crops are important components of copping systems due to their beneficial effects on soil physical, chemical, and biological properties. A greenhouse experiment was conducted to evaluate influence of phosphorus (P) fertilization on nutrient-use efficiency of 14 tropical cover crops. The P levels tested were 0 (low), 100 (medium), and 200 (high) mg kg−1 of soil. The cover crops tested were Crotalaria breviflora, Crotalaria spectabilis Roth, Crotalaria ochroleuca G. Don, Crotalaria juncea L., Crotalaria mucronata, Calapogonium mucunoides, Pueraria phaseoloides Roxb., Cajanus cajan L. Millspaugh, Dolichos lablab L., Mucuna deeringiana (Bort) Merr., Mucuna cinereum L., and Canavalia ensiformis L. DC. Agronomic efficiency (shoot dry weight per unit P applied), physiological efficiency (shoot dry weight per unit of nutrient uptake), and apparent recovery efficiency (nutrient uptake in the shoot per unit nutrient applied) were significantly varied among cover crops. Agronomic efficiency decreased with increasing P levels. Overall, physiological efficiency of nutrient uptake was in the order of P > sulfur (S) > magnesium (Mg) > calcium (Ca) > potassium (K) > nitrogen (N). Similarly, apparent recovery efficiency was in the order of N > K > Ca > Mg > P > S. Different recovery efficiency in cover crops can be useful in selecting cover crops with high recovery efficiency, which may be beneficial to succeeding crops in the cropping systems. The P × cover crops interactions were significant for soil extractable Ca2+, P, cation exchange capacity (CEC), Ca saturation, Ca/K ratio, and K/Mg ratio, indicating that cover crops change these soil property differently under different P levels. Thus, cover crops selection for different P levels is an important strategy for using cover crops in cropping systems in Brazilian Oxisols. Optimal values of soil pH, soil Ca and Mg contents, hydrogen (H) + aluminum (Al), P, CEC, base saturation, Ca saturation, Mg saturation, and K saturation were established for tropical cover crops grown on an Oxisol.