The role of tillage, fertiliser and forage species in sustaining dairying based on crops in southern Queensland 2. Double-crop and summer sole-crop systems

Abstract

Dairy farms located in the subtropical cereal belt of Australia rely on winter and summer cereal crops, rather than pastures, for their forage base. Crops are mostly established in tilled seedbeds and the system is vulnerable to fertility decline and water erosion, particularly over summer fallows. Field studies were conducted over 5 years on contrasting soil types, a Vertosol and Sodosol, in the 650-mm annual-rainfall zone to evaluate the benefits of a modified cropping program on forage productivity and the soil-resource base. Growing forage sorghum as a double-crop with oats increased total mean annual production over that of winter sole-crop systems by 40% and 100% on the Vertosol and Sodosol sites respectively. However, mean annual winter crop yield was halved and overall forage quality was lower. Ninety per cent of the variation in winter crop yield was attributable to fallow and in-crop rainfall. Replacing forage sorghum with the annual legume lablab reduced fertiliser nitrogen (N) requirements and increased forage N concentration, but reduced overall annual yield. Compared with sole-cropped oats, double-cropping reduced the risk of erosion by extending the duration of soil water deficits and increasing the time ground was under plant cover. When grown as a sole-crop, well fertilised forage sorghum achieved a mean annual cumulative yield of 9.64 and 6.05 t DM/ha on the Vertosol and Sodosol, respectively, being about twice that of sole-cropped oats. Forage sorghum established using zero-tillage practices and fertilised at 175 kg N/ha.crop achieved a significantly higher yield and forage N concentration than did the industry-standard forage sorghum (conventional tillage and 55 kg N/ha.crop) on the Vertosol but not on the Sodosol. On the Vertosol, mean annual yield increased from 5.65 to 9.64 t DM/ha (33 kg DM/kg N fertiliser applied above the base rate); the difference in the response between the two sites was attributed to soil type and fertiliser history. Changing both tillage practices and N-fertiliser rate had no affect on fallow water-storage efficiency but did improve fallow ground cover. When forage sorghum, grown as a sole crop, was replaced with lablab in 3 of the 5 years, overall forage N concentration increased significantly, and on the Vertosol, yield and soil nitrate-N reserves also increased significantly relative to industry-standard sorghum. All forage systems maintained or increased the concentration of soil nitrate-N (0–1.2-m soil layer) over the course of the study. Relative to sole-crop oats, alternative forage systems were generally beneficial to the concentration of surface-soil (0–0.1 m) organic carbon and systems that included sorghum showed most promise for increasing soil organic carbon concentration. We conclude that an emphasis on double- or summer sole-cropping rather than winter sole-cropping will advantage both farm productivity and the soil-resource base.

Productivity and profitability of forage options for beef production in the subtropics of northern Australia

“…Forage biomass yields for all three species of annual forage crop in the present study were generally at the upper end of the expected range for dryland crops in southern Queensland (Chataway et al 2011a(Chataway et al , 2011bBell et al 2012). The yields were similar to those reported for irrigated crops grown near Trangie, New South Wales (Muldoon 1985(Muldoon , 1986.…”

Organic and mineral fertilization management improvements to a double-annual cropping system under humid Mediterranean conditions

“…Oats as a double-crop with sorghum were highly productive: maximum yields (16.7 Mg ha -1 , Table 4) were close to maximum values (16.2 Mg ha -1 ) found in similar systems (Chataway, 2011) in Australia. Also, maximum rotation averages for the ryegrass-maize sequence (24.04 Mg ha -1 , Table 4) were close to maxima (24.6-27.6 Mg ha -1 ) obtained…”

“…Differences in the crop development stage at harvest, under different management systems, make it difficult to compare results in N content with references (Table 7), such as for the oat-sorghum sequence (Chataway et al, 2011). The high N concentration in sorghum (26.1 g N kg -1 ), in the third rotation (Table 7), was mainly due to the extreme 2012 summer drought which reduced yields (Table 4) Average N concentrations in ryegrass (from 9.2 to 14 g N kg -1 ) were close to the ones ( 8-10 g N kg -1 ) from Grignani et al (2007), and they were in the range obtained by Trindade et al, (2008) with values from 9.2 to 20.5 g N kg -1 .…”

Climate-smart cropping systems for temperate and tropical agriculture: mitigation, adaptation and trade-offs

“…Sequential multiple cropping (double or relay; main and cover crops) is often advocated as effective method for increasing crop productivity while protecting soil and storing more carbon (Chataway et al, 2011;Rao et al, 2015). In regions where water is limited, more irrigation will be necessary to make possible the summer growth of double crops or the establishment of cover crops at the end of summer (Meza et al, 2008).…”