Phosphorus deficit increases the production risk to a greater extent in wheat than in maize and soybean

LUIS MANENTI; GARCIA, FERNANDO O.; RUBIO, GERARDO

Montevideo

Congreso; 7th Symposium on Phosphorus in Soils and Plants (PSP7); 2022

National Agricultural Research Institute and School of Agronomy, Universidad de la República, Uruguay

The production risk approach allows the estimation of the probability that the yield of a cropping system fallsbelow a certain threshold. By comparing this probability between different crops or agronomic practices, it ispossible to choose between different interventions to mitigate the effects of risk and foster resilience. Ourobjective was to compare the effects of long-term P fertilizaton on production risks in maize, wheat, and fullseason (FS) and double cropped (DC) soybean. Evaluations focused on a long-term experiment being conductedin five farms located in the Northern Pampas Region of Argentina since 2000, comparing +P (with P) and -P(without P) treatments. The effect on yield (tn ha-1) and production risk calculated by the probability (%) of yieldsfalling below critical levels every 0.1 tn ha-1 were estimated. As expected, the four crops presented higher yieldswith P application, the average response was 1.17, 1.03, 0.30 and 0.44 (tn ha-1) for maize, wheat, FS soybeanand DC soybean, respectively. The relative risk plots contrast graphically the agronomic production risks of onefertilization treatment versus another taken as reference, in our case -P and +P. The absence of P fertilizationdifferentiated two groups. The lower production risk was verified for maize and both soybean crops (FS/ DC),which presented small differences between them. The wheat curve remained clearly separated from the firstgroup, showing a greater concavity which indicates a higher production risk. In all cases, the -P treatmentpresented the highest production risk with a yield probability below the mean of 61, 69, 59 and 64% for maize,wheat, FS and DC soybean, respectively. For the +P treatment these values were reduced to 40, 33, 41 and 42%.Obtained results allowed the quantification of the differential impact of P fertilization on the production risk ofthe main Pampean crops.