Break crops and rotations for wheat

Abstract

Wheat grown after Brassica crops normally yields more than wheat grown after wheat. Previously we reviewed 33 experiments and concluded that wheat after canola yielded about 19 % more than wheat after wheat and that the gross margin of a canola-wheat sequence was 27 % greater than a wheat-wheat sequence. Further analysis of other published, replicated experiments revealed that the mean increase in wheat yield after brassicas was better represented as a fixed amount rather than a percentage. The mean yield benefit of canola (B napus) to subsequent wheat yield was similar (0.8 t ha-1) over 180 experiments where wheat yield varied from 1.1 to 9.5 t ha -1. Over 36 experiments where canola and juncea canola (B juncea) were compared the break-crop effects were identical at 0.6 t ha -1 . Part of the reason for the additional wheat yield is increased uptake of soil water and nutrients, which may explain the fixed, rather than percentage, increase in mean yield as a response to the limited supply of these resources. The earlier conclusion about canola-wheat providing a 27 % increase in gross margin over wheat-wheat must be revised since the financial benefit is relatively greater at low levels of wheat yield. A canola-wheat sequence provided an 85% increase in gross margin over wheat-wheat at low (2 t ha -1 ) yield levels but only 3% at high (6 t ha -1 ) yield levels.

Cost of root disease on white clover growth in New Zealand dairy pastures

“…In addition to a direct cost on plant productivity, rootdisease pressure also contributes indirect costs associated with reduced nutrient and water-use efficiency (Baligar et al 2001;Angus and Van Herwaarden 2001;Angus et al 2015). However, much of the work conducted in this area has been in arable cropping systems, and the indirect cost of root disease on nutrient and water use efficiency in pastoral systems Fig.…”

Efecto De Pre-Cultivos Hospederos Y No Hospederos en El Crecimiento Y Propágulos Micorrícicos De Trigo en Andisol E Inceptisol De Chile

“…que les permite asignar el crecimiento de forma selectiva a los órganos que captan más de un recurso limitante (Angus et al, 2015). En el primer año de la rotación, la colonización por hongos MA en las raíces de avena, en And alcanzó 35%, mientras que en Inc fue levemente menor, con 31% (Castillo et al, 2008).…”

Nitrous oxide emissions from grain production systems across a wide range of environmental conditions in eastern Australia

“…In previous studies, the yield of wheat after legumes generally exceeded the yield of wheat after wheat (Angus et al 2015), partly due to increased N availability after legumes. This discovery supports our finding of a reduced N rate at which the yield plateau was reached for wheat and sorghum in rotation with legumes than in monoculture.…”

“…Legumes are increasingly being proposed as break crops in grain cropping systems to control weeds and diseases (Angus et al 2015) and, particularly in the case of high-value pulses, as a valuable commodity in their own right. Including a legume in the crop rotation increased yields at lower N rates and reduced the N rate at which the yield plateau was reached compared with monoculture cereals.…”