Download Advances in Agronomy v106 by Donald L. Sparks (Eds.) PDF

By Donald L. Sparks (Eds.)

Advances in Agronomy is still famous as a number one reference and a primary resource for the most recent examine in agronomy. As continuously, the topics lined are diversified and exemplary of the myriad of material handled through this long-running serial. * continues the top impression issue between serial courses in agriculture * provides well timed experiences on vital agronomy matters * Enjoys a long-standing recognition for excellence within the box

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Partly offsetting the dewatering ability of lucerne is greater infiltration into the subsoil through taproot channels, which remain in the soil for several years after roots decay. McCallum et al. (2004) found that the average infiltration into subsoil after lucerne was 10 mm more than into subsoil where annual pastures or crops had grown. This amount is not enough to compensate for the buffer at the end of a lucerne phase but after the soil profile is recharged during the cropping phase, the greater infiltration provides a continuing benefit.

Poor distribution of rain can account for some of the yields falling well below the line, but there are many other reasons as well: untimeliness of operations (especially late sowing), weeds, poor establishment of seedlings, disease, inadequate nutrition, frost, heat, excessively acid topsoil, and subsoil that is inhospitable to roots because of sodicity, boron toxicity, salinity, acidity, or alkalinity. Some of these, especially root diseases and inhospitable subsoil, reduce the roots’ ability to take up water and can be partly alleviated by more rain.

Passioura and J. F. Angus Wheat yield (tonne/ha) 6 Water-limited potential yield 5 4 3 2 Evaporation from soil 1 0 0 100 200 300 Water use (mm) 400 500 Figure 1 Schematic portrayal of wheat yield in relation to seasonal water supply (rainfall during the growing season plus available water in the soil at the time of sowing). The solid line depicts yield if water is the only limitation. It has a slope of about 20 kg haÀ 1 mmÀ 1. The intercept of that line on the x-axis reflects the loss of water by direct evaporation from the soil.

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