Comparing the climate experienced during the Cicerone farmlet experiment against the climatic record

Abstract

Abstract. Farming systems research conducted under dryland conditions is subject to the vagaries of the climate during the experimental period. Whether such an experiment experiences a representative series of climatic years must be examined in relation to the longer term climatic record. The Cicerone Project's farmlet experiment was conducted on the Northern Tablelands of New South Wales, Australia, to investigate the profitability and sustainability of three different management systems: one managed under typical, moderate-input conditions (farmlet B); a second which employed a higher level of pasture inputs and soil fertility (farmlet A); and a third which focussed on the use of moderate inputs and intensive rotational grazing (farmlet C).The climate experienced during the 6.5-year experimental period was compared with the 118-year climatic record, using a biophysical simulation model of grazed systems. The model utilised the long-term daily climate data as inputs and provided outputs that allowed comparison of parameters known to affect grazed pastures. Modelled soil-available water, the number of soil moisture stress days (SMSDs) limiting pasture growth, and growth indices over the experimental period (2000-06) were compared with data over the climatic record from 1890 to 2007. SMSDs were defined as when the modelled available soil moisture to a depth of 300 mm was <17% of water-holding capacity. In addition, minimum temperatures and, in particular, the frequency of frosts, were compared with medium-term (1981-2011) temperature records.Wavelet transforms of rainfall and modelled available soil water data were used to separate profile features of these parameters from the noise components of the data. Over the experimental period, both rainfall and available soil water were more commonly significantly below than above the 95% confidence intervals of both parameters. In addition, there was an increased frequency of severe frosting during the dry winters experienced over the 6.5-year period. These dry and cold conditions were likely to have limited the responses to the pasture and grazing management treatments imposed on the three farmlets. In particular, lower than average levels of available soil water were likely to have constrained pasture production, threatened pasture persistence, and reduced the response of the pasture to available soil nutrients and, as a consequence, livestock production and economic outcomes.Ideally, dryland field experimentation should be conducted over a representative range of climatic conditions, including soil moisture conditions both drier and wetter than average. The drier than average conditions, combined with a higher than normal frequency of severe frosts, mean that the results from the Cicerone Project's farmlet experiment need to be viewed in the context of the climate experienced over this 6.5-year period.

Grazing systems and worm control in sheep: a long-term case study involving three management systems with analysis of factors influencing faecal worm egg count

“…As described in a related paper by Behrendt et al (2013), the climate experienced over the experimental period was in general drier than average, especially over the autumn-spring period, and experienced more severe frosts than average. Climatic data over the long-term from 1890 to 2008 were used as inputs to the model Ausfarm, which permitted the estimation of changes in available soil water (ASW) over both the long-term and the experimental period (Behrendt et al 2013). The same climatic data were used to estimate the potential effects of temperature on gastrointestinal nematodes and pasture growth as the average of growing-degree days (GDD) calculated using base temperatures of 4 C for grasses and 10 C for clovers [((max.…”

“…The average annual rainfall is~790 mm. The weather experienced during the trial period was mostly drier than average with more severe frost in winter than average (Behrendt et al 2013). The farmlet experiment commenced on 1 July 2000 following the subdivision of the three farmlets, each of 53 ha, which were managed under three different management systems described in detail by Scott et al (2013b).…”

Whole-farm management of soil nutrients drives productive grazing systems: the Cicerone farmlet experiment confirms earlier research

“…First, as noted by Jones et al (1995), the effects of changes in soil fertility and its interactions with botanical composition and SR are commonly observed to change over many years; in the present experiment, pasture renovation continued from 2000 up until 2004 while soil fertility differences were imposed especially over the first 3 years of the trial, resulting in farmlet parameters not reaching plateau conditions (Saul 2005) during the trial. Second, as demonstrated by Behrendt et al (2013b), the soil moisture conditions experienced throughout the trial were below long-term median levels, thus limiting the expression of soil fertility changes as they affect pasture growth. Third, due to project resource constraints, fertilisers were not able to be applied in the last 2 years of the trial, which limited the ability to consistently maintain the target soil fertility levels on each of the farmlet treatments.…”

“…The rainfall and climate experienced over the 6.5 years of the trial has been summarised in Behrendt et al (2013b). In brief, the trial experienced below-median soil moisture conditions over most of the trial period and more frequent severe frosts during winter of the majority of years, thus constraining the responses to the farmlet treatments.…”

Delivering extension and adult learning outcomes from the Cicerone Project by ‘comparing, measuring, learning and adopting'

“…During the Project, the rainfall received was generally below average with extended periods of below-average soil moisture and above-average severe frosting (Behrendt et al 2013b). These conditions meant that, during the trial, there was an ongoing need for appropriate information such as the demonstration of Prograze R methods of pasture and animal assessment held during autumn and winter as well as other technical days, such as Stockplan R workshops to help producers understand and support their decisions.…”