Water- and solar radiation-productivity in no-till forage cropping systems in the south-east Pampas of Argentina

2. OJEDA, J.J.; CAVIGLIA, O.P.; AGNUSDEI, M.G.; ERRECART, P.M.

Congreso; 7th World Congress on Conservation Agriculture; 2017

LivestockArgentinian systems show a current process of change in the forage base composition,with an ongoing increase in the proportion of their area assigned to annualcrop sequences (ACS) at the expense of the area assigned to cultivated perennialpastures (PP). However, there are several concerns about efficient use ofavailable resources due to differences in the length of crop establishment andfallow periods, as well as the crops involved in these systems. Therefore, the aimof this work was to assess the water (WP) and solar radiation productivity (RP)of fertilized and unfertilized PP and ACS through the analysis of theircomponents, water (WU) and radiation uptake (RU), and water (WUE) and radiationuse efficiency (RUE). Resource uptake (WU and RU) is the ratio between theuptaked (evapotranspiration and intercepted solar radiation) and annualavailable resource (precipitation and incident solar radiation). Resource useefficiency (WUE and RUE) is the quotient between biomass production and uptakedresource. A two-year field experiment was conducted under no-till drylandconditions in the south-east Pampas of Argentina. The differences in resource uptakebetween PP and ACS were directly related with the nature of the consideredresource. When PP were not fully established, the WU was higher for ACS(0.92-1.05) than for PP (0.77-0.83) (P<0.05). On the other hand, RU wasstrongly dependent on the length of crop establishment and fallow periods. Indeed,once PP were completely established, RU of ACS (0.51-0.53) was lower than RU ofunfertilized (0.59-0.62) and fertilized PP (0.68-0.74). A curvilinear associationbetween WUE and RUE was found. However, for RUE values up to ~2-2.5 g m-2 MJ-1 this association waslinear, which in this range included all treatments except maize-oats in thefirst year of evaluation. The highest WP (2.75-3.64 gm-2 mm-1) and RP (0.93-1.42 g m-2 MJ-1) were achieved by ACS, whichdid not differ (P>0.05) from completely established fertilized PP. Ourresults confirmed that resource productivity in ACS was not necessarily higherthan in PP. Accordingly, ACS were similar to PP in resource productivity, oncePP were completely established and under optimal N availability.