Modelling inter-annual variation in dry matter yield and precipitation use efficiency of perennial pastures and annual forage crops sequences

OJEDA, JONATHAN JESUS; AGNUSDEI, MÓNICA GRACIELA; CAVIGLIA, OCTAVIO PEDRO; IRISARRI, JORGE GONZALO NICOLÁS

AGRICULTURAL AND FOREST METEOROLOGY

ELSEVIER SCIENCE BV

Año: 2018 vol. 259 p. 1 - 10

0168-1923

In livestock systems of the Argentinean Pampas, its forage production stability relies on the integration of twolandcovers, annual forage crop sequences and perennial pastures. Despite the key role that these forage croppingsystems have on current milk and beef production, it is unclear how year-by-year variability of precipitationaffect forage dry matter (DM) yield and precipitation use efficiency (PUE, i.e. the quotient between forage DMyield and precipitation). The aims of this study were to analyze the impact (i) of year-by-year precipitationvariability on DM yield and PUE of oats-maize (Avena sativa L. - Zea mays L.) double-crop and alfalfa (Medicagosativa L.) and (ii) of cumulative precipitation during the critical period of maize on DM yield and PUE of oatsmaizedouble-crop. We used a modelling approach to estimate DM yield and PUE of oats-maize (sequence) andalfalfa in five locations of the Argentinean Pampas, which differed in annual precipitation (AP) and variability ofit. Coefficient of variation (CV) was used as the main statistical variable to compare the variability of AP (CVAP),DM yield (CVDM), and PUE (CVPUE). Mean DM yield of both landcovers was higher in locations with high AP(> 800 mm) than with low AP (< 800 mm). Although alfalfa had lower mean DM yield than sequence in alllocations, it showed a lower CVDM than sequence. In contrast, sequence showed lower and higher CVDM thanCVAP, depending on location. Moreover, changes in DM yield due to variations of AP were higher in sequencethan in alfalfa. On the other hand, mean PUE was higher for sequence (2.2 g DM m−2mm−1) than that of alfalfa(1.6 g DM m−2mm−1). The CVPUE between locations, i.e. an index that reflects the spatial variability, rangedfrom 20 for the sequence to 68% for alfalfa, whereas CVPUE between years, i.e. an index that reflects the temporalvariability, ranged from 16 to 31 % for both landcovers. Precipitation use efficiency tended to be similar acrosslocations in years with low AP (< 800 mm) compared to years with high AP (> 800 mm). Our results providedvaluable knowledge for decision making in livestock systems of this region through the development of spatialand temporal models between DM yield and AP. In a broader sense, they also showed that shifts from perennialto seasonal forage covers increased yields but also its inter-annual variability, posing a risk for farmers.