Growth of shoots and roots, and interception of radiation by wheat and lupin crops on a shallow, duplex soil in response to time of sowing

Abstract

Crops of lupin (Lupinus angustifolius L. cv. Gungurru) and wheat (Triticum aestivum cv. Kulin or Spear) sown close to the break of the season and 3-6 weeks later were grown on a duplex soil at East Beverley, WA, over 3 seasons. The overall aim of the work was to examine the influence of time of sowing on growth and water use of the crops, and this paper reports their growth and yield. Early sowing resulted in greater shoot weight of all crops (up to 2.8 t/ha for lupin and 1.7 t/ha for wheat at maturity) and grain yield of lupin, but grain yield of wheat was increased in only 1 of the 3 seasons. The principal effect of the delayed sowing was to reduce the duration of linear growth; the rate of the initial exponential phase was slightly reduced by later sowing as was the rate of growth during the linear phase in lupin (by about 1.5 g/m2day) but not in wheat. Late sowing generally reduced both the number of pod/ears per unit area and the number of grains per pod/ear. Doubling the density of sowing in one of the seasons had no effects on the shoot weight and grain yield of lupin with early or late sowing but decreased those of wheat. Downward root growth of early-sown crops averaged 5.2 mm/day for lupin and 8.7 mm/day for wheat in the 3 seasons and ceased at about 0.8 m; time of sowing had no effect on these measures. Root weight at flowering was greater in lupin than in wheat crops, and root weight of lupin was about 0.5 of total plant weight during vegetative growth compared with 0.25-0.3 in wheat. Typically, only 5-6% of the root length of both crop species was present in the clay layer at flowering irrespective of sowing time. The proportion of radiation intercepted reached a higher maximum value for early-sown crops (about 0.75 in 1991 and 0.90 in 1992) than late-sown crops (about 0.60 in 1991 and 0.8 in 1992). The conversion coefficients of radiation to dry matter were very similar (about 1.8 g/MJ) for both species, but the greater partitioning of dry matter to roots in lupin than wheat meant that conversion coefficients for shoot dry matter were greater in wheat (1.43-1.68 g/MJ) than in lupin (0.93-1.16 g/MJ). The results demonstrate that early sowing produced larger crops of both lupin and wheat; this resulted in larger lupin yields, but yield of wheat was affected by disease and drought during grain filling.

Winter wheat roots grow twice as deep as spring wheat roots, is this important for N uptake and N leaching losses?

“…We estimated root depth penetration rates of approximately 1.3 mm o C day −1 for both spring and winter wheat, close to some of the rates found by Kirkegaard and Lilley (2007) in kandosol soils, but higher than those found by Gregory and Eastham (1996) and Tennant (1976) on duplex sands over clay soils. Lower rates of rooting depth can be related to soil compaction (Dracup et al 1992;Unger and Kaspar 1994) or not fully wetted soil profiles (Kirkegaard and Lilley 2007).…”

Simulating lupin development, growth, and yield in a Mediterranean environment

“…The soil was the same as in experiment 4. Details are published by Gregory and Eastham (1996) and Gregory (1998).…”

“…The extinction coefficient describes the shape of the relationship between LAI and fraction of radiation intercepted. A value of K = 0.85, commonly reported (Gregory and Eastham 1996;Thomson and Siddique 1997), was used in the model. A value of RUE of 0.8 g/MJ solar radiation reported by Gregory and Eastham (1996) and Thomson and Siddique (1997) for narrow-leafed lupin cultivars was used in the model.…”

“…A value of K = 0.85, commonly reported (Gregory and Eastham 1996;Thomson and Siddique 1997), was used in the model. A value of RUE of 0.8 g/MJ solar radiation reported by Gregory and Eastham (1996) and Thomson and Siddique (1997) for narrow-leafed lupin cultivars was used in the model. Values of RUE ranging from 0.7 to 0.8 g/MJ solar radiation were also derived from measurements of shoot biomass and intercepted radiation for different cultivars in Expt 13 (data not shown).…”

Grain yield and phosphorus use efficiency of wheat and pea in a high yielding environment

“…However, the link between root diameter and P uptake is still unclear. In general, temperate cereals, such as wheat and barley have higher root length and specific root length than legumes under different water regimens (Gregory and Eastham 1996). However, legumes could compensate for their lower root length through a higher P uptake per unit of root length, since legumes have shown higher organic exudation than wheat (Nuruzzaman et al, 2006;Pearse et al, 2006); this increases P mobility and uptake (Hinsinger, 2001;Yang et al, 2013).…”