Forage yield, water- and solar radiation-productivities of perennial pastures and annual crops sequences in the south-eastern Pampas of Argentina

• Published in: Field crops research 2018-05, Vol.221, p.19-31
• Main Authors: Ojeda, J.J., Caviglia, O.P., Agnusdei, M.G., Errecart, P.M.
• Format: Article
• Language: English
• Subjects: Alfalfa; Forage crop intensification; Livestock systems; Maize; Nitrogen; Tall fescue
• ISSN: 0378-4290; 1872-6852
• DOI: 10.1016/j.fcr.2018.02.010

•We compared forage crop sequences and temperate perennial pastures.•Perennial pastures, once established and well N fertilized, were as productive as forage crop sequences.•Radiation capture was reduced by the length of periods with low vegetal cover.•Water capture was less affected by treatments than radiation capture.•We mechanistically accounted for the two components of water- and radiation-productivities. Livestock production systems of Argentina show an ongoing process of change in the composition of their forage base, with a gradual increase in the proportion of their area assigned to forage crop sequences (FCS) −in particular that involving successive winter and summer annual forage crops–, at the expense of the area assigned to perennial pastures (PP). However, there are several concerns regarding the efficient use of available environmental resources due to differences in the extent of the establishment periods and due to the occurrence of fallow periods in FCS, as well as regarding the species involved in these systems. Therefore, the main objective of this study was to evaluate the water (WP) and solar radiation productivity (RP) of PP [pure stands of alfalfa (Medicago sativa L.), fertilized and unfertilized stands of tall fescue (Festuca arundinacea Schreb.), and fertilized and unfertilized mixed stands of alfalfa/tall fescue] and FCS [including a summer alternative and oats (Avena sativa L.); the summer alternative was either maize (Zea mays L.) or intercropped maize/soybean (Glycine max L.)] through the analysis of their components, i.e. water (WC) and radiation capture (RC), and their water (WUE) and radiation use efficiency (RUE). Resource capture (WC and RC) was defined as the ratio between captured (evapotranspiration and intercepted solar radiation) and annual available resource (rainfall and incident solar radiation). Resource use efficiency (WUE and RUE) was computed as the dry matter (DM) yield per unit of captured resource. A field experiment was conducted during two consecutive years under rainfed conditions and under non-limiting nitrogen availability in the south-eastern Pampas of Argentina. Perennial pastures were evaluated during both their initial establishment year (Y1) and when already fully established (Y2). Annual-based forage DM yield ranged between 13.0 and 32.4 Mg ha−1 in Y1 and between 5.1 and 23.5 Mg ha−1 in Y2. Differences in resource capture between PP and FCS were directly associated with the crop establishment an