Yield Response to Nitrogen and Phosphorus of Maize and Soybean in Argentine Pampas.

Yield response to fertilization depends on multiple factors including both, crop and soil characteristics. General patterns of this response are difficult to derive from single experiments. Systematic review and meta-analysis techniques of large datasets are useful methodologies for studying these response patterns. In order to study maize yield response to nitrogen (N) fertilization in maize and phosphorus (P) addition in maize and soybean in Argentina, data from ca. 490 and 250 experiments of N and P in maize, and 450 of P experiments in soybean were gathered. Most part of data comes from what is so-called grey literature (non-published on peer-review journals). In many cases, researchers who conducted the experiments were asked to meet the minimum data requirements. Despite the wide covered range of rainfall, soil, and crop management conditions, pre-plant nitrate-N test (PPNT, 0-60cm) plus fertilizer N explained 36% of maize yield variation. Yield response to N varied from -1349 to +10110 kg ha^-1, which represented relative responses of -11.8% to +189 %. In terms of efficiency, the N agronomic efficiency (NAE) ranged from -33 to 110 kg grain per kg of N fertilizer, and increases of available N (PPNT + N fertilizer) exponentially decreased its partial productivity (15 to 754 kg grain per kg of available N). In the case of P fertilization, grain yield responses ranged from -990 to +6722 kg ha^-1 in maize, and from -1636 to +3233 kg ha^-1in soybean. In the same order, PAE ranged from -49 to +195 kg maize, and -182 to +234 kg soybean per kg of P fertilizer.  Soil test-P (STP, 0-20cm) explained most of the variation in yield response and PAE for both, maize and soybean. Relative yield (unfertilized:fertilized) was associated with STP, and estimated STP threshold did not show consistent differences between both crops.