Soil Moisture Deficit as a predictor of the trend in soil water status of grass fields

Abstract

Nutrient loss from agricultural land following organic fertilizer spreading can lead to eutrophication and poor water quality. The risk of pollution is partly related to the soil water status during and after spreading. In response to these issues, a decision support system (DSS) for nutrient management has been developed to predict when soil and weather conditions are suitable for slurry spreading. At the core of the DSS, the Hybrid Soil Moisture Deficit (HSMD) model estimates soil water status relative to field capacity (FC) for three soil classes (well, moderately and poorly drained) and has potential to predict the occurrence of a transport vector when the soil is wetter than FC. Three years of field observation of volumetric water content was used to validate HSMD model predictions of water status and to ensure correct use and interpretation of the drainage classes. Point HSMD model predictions were validated with respect to the temporal and spatial variations in volumetric water content and soil strength properties. It was found that the HSMD model predictions were well related to topsoil water content through time, but a new class intermediate between poor and moderate, perhaps ‘imperfectly drained’, was needed. With correct allocations of a field into a drainage class, the HSMD model predictions reflect field scale trends in water status and therefore the model is suitable for use at the core of a DSS.

Climate change and soil wetness limitations for agriculture: Spatial risk assessment framework with application to Scotland

“…These data were used to derive a water balance for each grid cell by calculating a soil moisture deficit for those times during the year when potential evapotranspiration (PET) exceeded precipitation, following previously established procedures for land capability (Brown et al, 2008). Soil moisture deficit provides a reliable indicator of seasonal variations in the soil water regime relative to a zero deficit condition when the soil is totally saturated and defined as being at field capacity (Kerebel et al, 2013;Premrov et al, 2010). PET was calculated from UKMO climate data (maximum temperature, minimum temperature net radiation, relative humidity, wind speed) according to the FAO56 method with sunshine duration used to estimate net radiation values (Allen et al 1994;Pereira et al, 2015).…”

Assessing the production and economic benefits from preventing cows grazing on wet soils in New Zealand

“…Restricted grazing strategies, which include deferred grazing, have also been proposed as a way to protect soils and pasture from animal treading damage that occurs when cows graze wet soils . In Europe, dairy cows are traditionally kept indoors on a full‐time basis during wet periods and fed a grass silage‐based diet .…”

“…The Proctor test methodology can be used to determine a critical water content (CWC) for a given soil beyond which it will be compacted under an applied load . The CWC can be used to guide stock grazing management decisions …”

“…3 -5 Restricted grazing strategies, which include deferred grazing, have also been proposed as a way to protect soils and pasture from animal treading damage that occurs when cows graze wet soils. 6 -10 In Europe, dairy cows are traditionally kept indoors on a full-time basis during wet periods and fed a grass silage-based diet. 11 -13 However, in New Zealand, farmers generally do not remove cows from paddocks in response to adverse weather, and farm management practices that defer pasture grazing in response to a high SWC are a relatively new concept.…”

“…18 The CWC can be used to guide stock grazing management decisions. 6,19 Holding cows off paddock increases a farm's required capital and operating expenditure through provision of a stand-off pad and associated effluent management system, increased labour inputs and the need for a supply of quality supplementary feed. 20,21 Generally, both the capital and operating costs are similar across regions (i.e.…”