ALBERT

Description: SummaryPulverized fuel ash and fiuidized combustor ash were used to modify the availablewater capacity and moisture characteristics of a gravelly sandy loam soil in a study of the effects of fine-particle amendments on crop yield. Intimate incorporation of the ashes into the top-soil at rates of up to 502 t/ha increased the available water retained in the surface 0·3 m of soil by 40–80 %. The increase was mainly water held at potentials of between –0·05 bar and – 1 bar.Two sugar-beet crops followed by broad beans, salad onions and cabbage were grown in the amended soil. With the highest rate of ash addition yield of the onions was increased by over 30% and of the cabbages by 14%. No improvement in sugar-beet or broad-bean yields resulted from the treatment. Poor growth of the second sugar-beet crop was attributed to a reduced aeration effect but it is suggested that the failure of the increased available water to improve yield consistently in this and a previous experiment was in part caused by rapid evaporative losses from the amended soil.

Description: SUMMARYExperiments were made on a sandy clay loam soil with five crops to determine the effects of thorough loosening of the subsoil and deep incorporation of nutrients on yields during the subsequent 4 years.Loosening to 0·9 m increased fresh-weight yields by between nil and 95% depending on the crop and season. Responses were still considerable 4 years after the initial loosening and there was no evidence of any decline with time. Deep incorporation of nutrients did not improve yields.Loosening gave a durable increase in the volume of coarse pores and decreases in bulk density and penetrometer resistance. It also nearly doubled the rate of root extension when estimates were made for one crop, consistently increased water extraction from below 30 cm and, on occasion, reduced plant water stress.It is concluded that most of the benefits from deep loosening resulted from improvements i the rate at which plants could extract water rather than nutrients from the subsoil.

Description: SUMMARYThe relationships of normalized water index three (NWI-3) and canopy temperature (CT) with grain yield in north-west Mexico were determined in a set of wheat lines planted in multi-location yield trials. Advanced wheat lines developed by The International Maize and Wheat Improvement Centre (CIMMYT) were included and tested internationally in the trials including the 24th Elite Spring Wheat Yield Trial (ESWYT), the 11th Semi-Arid Wheat Yield Trial (SAWYT) and the 11th High Temperature Wheat Yield Trial (HTWYT). In north-west Mexico, NWI-3, CT and grain yield were determined in three growing seasons (2006, 2007 and 2008) and three environments (well irrigated, water-stressed and high-temperature), while grain yield was measured at international locations in the same advanced lines of the 24th ESWYT, the 11th SAWYT and the 11th HTWYT . The CIMMYT database was used to obtain grain yield from worldwide nurseries. The mean grain yield ranged from 0·8 to 12·7 t/ha for the 24th ESWYT (59 international sites), from 0·6 to 8·2 t/ha for the 11th SAWYT (28 international sites) and from 0·4 to 7·5 t/ha for the 11th HTWYT (26 international sites). NWI-3 and CT for the advanced lines in the three yield trials measured in north-west Mexico in distinct environments showed significant associations with the grain yield from a few international locations (0·12–0·23 of sites). Locations from Central Asia and North Africa had the best associations with NWI-3 and CT. The lack of more associations may be due to either an interaction of other factors (low rainfall and limited irrigations), which affected yield performance, or few of the advanced lines were well adapted to local growing conditions at each testing site, or a combination of these factors. The present results indicate that NWI-3 and CT have limited potential to predict yield performance at international sites.

Description: Annual liveweight gain of beef cattle (steers) grazing grass pasture fertilized with 200 kg N/ha was compared over a period of 7 years (1989–95) with that of steers grazing grass/white clover pasture given no artificial N fertilizer at North Wyke, Devon, UK. Nitrogen lost by leaching over the ensuing winter drainage periods was monitored from both pastures. Nitrogen leaching loss from the fertilized pasture over an extended period of 13 years (1983–95) is also reported.The average annual liveweight gain of the steers grazing the grass/clover pasture (0·81 t/ha) was 19% lower than that of the steers grazing the N-fertilized grass pasture (1·00 t/ha). The average annual loss of nitrate-N by leaching in winter drainage from the grass/clover pasture (13 kg/ha) was only 26% of that recorded from the fertilized grass (50 kg/ha). A possible reason for this difference may arise from the previous history of the grass/clover pasture which had been ploughed in 1982, causing a flush of N mineralization and consequently greater immobilization of N in the soil in subsequent years.Losses of N each winter by leaching measured over a 13-year period from the fertilized grass were highly correlated (P