Nutrient loss from vegetable fields represents an economic loss to growers and a preventable source of environmental damage. Vegetable crops are prone to nutrient loss because of; a) high rates of application of highly soluble, leaching prone fertilizers, b) limited crop recovery of applied nutrients due to the limited rooting system and short cropping duration typical of vegetable crops, c) the concentration of vegetable crop production on coarse textured soils that are prone to nutrient loss through both erosion and leaching.
Hartz (Hort-Technology 2006 p 390-402) and others suggest the following methods that will help vegetable growers to increase fertilizer use efficiency and/or to reduce nutrient losses;
a) base fertilizer applications on recommendations that are appropriate to your region, method of production, cropping duration, anticipated yield potentials etc. Recommendations developed for growers in California are usually not appropriate for growers in Saskatchewan.
b) base fertilizer applications on the results of soil tests rather than on past practices, and then use in-season tissue tests to confirm that the resulting soil nutrient levels are suitable for optimal crop development
c) use appropriate methods of fertilizer application – surface applied nutrients are more prone to loss by surface run off and volatilization than fertilizers incorporate at the time of application. In row crops the total amount of fertilizer applied can be significantly reduced by concentrating the nutrients in bands adjacent to the crop rows.
d) time nutrient application to match crop needs. Heavy applications of nitrogen fertilizers prior to planting are generally undesirable as the N needs of developing seedlings are limited, leaving the fertilizer N open to loss by denitrification and leaching. As the crop develops, N requirements tend to increase – these needs can be most efficiently and accurately met by split applications of N, delivered by side-banding or through the irrigation system. As fall approaches, it may be desirable to cut back on the N applications to encourage the crop to mature.
e) timely, accurate and uniform irrigation will increase crop growth without causing nutrient loss through run off or leaching
f) once the crop has been harvested plant cover crops to reduce nutrient loss by wind erosion and surface run
e) use deep-root rotational crops to return any nutrients that have been leached deep into the soil back to the soil surface where they will be available to subsequent vegetable crops. In Saskatchewan, fall planted rye does an excellent job of e) and f).
Source : Hartz (2006) Hort-Technology, pp. 390-402