Influence of Salinity and N‐P Fertility Levels on Mineral Content and Growth of Sorghum in Sand Culture¹

Abstract

Plant growth is characteristically depressed at certain levels of salt concentrations yet it sometimes responds to fertilizers even though growth depression can be expected to reduce nutrient requirements and even though fertilizer application increases salinity to some degree. This study was designed to examine tension zones involving interactions between nutrient supply (N and P) and salt concentrations. Grain sorghum (Sorghum bicolor (L.) Moench) was chosen for this study because it is commonly grown in regions of irrigated agriculture where soil salinity is often a problem. Plants were grown to maturity in automatically operated sand culture equipment at two levels each of N and P, each subjected to added Ca‐Na chloride salinity levels of zero, medium (EC = 10 mmho/cm) and high (EC = 20 mmho/cm). Vegetative growth was depressed to about 50% of control at both medium and high salinity, while grain production was depressed to about 35% at medium salinity and to almost none at high salinity. Chemical composition of leaves, in addition to familiar dilution effects and ion competition, revealed increased accumulation of Ca, Na, and CI related to high level of P supply, at high salinity only. When sorghum was grown at salinity levels that permitted reasonable grain production, maintenance of optimum soil fertility was important. However, the required level of nutrient supply was lower in saline than in nonsaline soils because of reduced growth. A critical balance between optimum nutrition and increased salinity from applied fertilizers was also involved.

Potassium-salinity interactions in irrigated corn

“…The latter effect is in agreement with the results of Lunin and Gallatin (1965) but contradicts the results of Khalil et al (1967) for cotton. Increasing K contents as well as other nutrient concentrations in corn and sorghum tissue caused by salinity have been reported by Selassie and Wagenet (1981) and by Patel et al (1975), respectively. This increase in K concentration in the tissue caused by salinity resulted from the sharp reduction in plant weight while K availability was unaffected.…”

Interactions of oxygen‐nitrogen‐salinity stresses on plant growth and mineral content of sunflower (Helianthus annuus L.) in sand culture

“…(17,18). Although nitrogen fertilization increased plant growth, there appears to be a critical nitrogen level, Patel et al (14), which will increase plant tolerance to saline stress. However, greater additions of nitrogen …”

“…Others have reported that ion accumulation may be affected by soil salinity and fertility levels (4,8,12,14,15,20). Root cell division, mineral content and growth of plants also appear to be modified by soil oxygen and/or fertility levels (10,13,18).…”

“…Root cell division, mineral content and growth of plants also appear to be modified by soil oxygen and/or fertility levels (10,13,18). The influence of gas composition and salinity on plant growth and development may be further compounded by nitrogen fertility (1,14). Patel et al (14) reported optimum Downloaded by [University of Florida] at 12:20 13 June 2016 nitrogen and phosphorus fertility levels for sorghum became more critical as soil salinity increased.…”

“…The influence of gas composition and salinity on plant growth and development may be further compounded by nitrogen fertility (1,14). Patel et al (14) reported optimum Downloaded by [University of Florida] at 12:20 13 June 2016 nitrogen and phosphorus fertility levels for sorghum became more critical as soil salinity increased. Nitrogen and phosphorus requirements for each stage of growth were also modified by salinity.…”