(I) Inorganic components . . . . . . . (a) Nitrate . . . . . . . . . (b) Cation-anionuptake . . . . . . (2) Organic compounds . . . . . . . (a) Amino acids and other organic nitrogenous compounds (b) Organic acids . . . . . . . . (3) Effects on flowering . . . . . . . (4) Ammonium plus nitrate as a nitrogen source . . . ( 5 ) Metabolic changes characteristic of ammonium toxicity . VII . Summary . . . . . . . . . . VI . Physiological effects of nitrogen sources . . . .

Ammonium and nitrate nutrition of plants

Soil Salinity under Irrigation

Loss of crop productivity from excess soil salinity is a worldwide problem. In arid and semi-arid regions salinity is a continual threat; but even in humid areas salinity is a hazard when irrigating with brackish water or treated sewage effluent, or because of seawater intrusion. Although soil salinity can sometimes be moderated by applying appropriate water management practices, adverse levels of soil salinity are often difficult to prevent because of a lack of nonsaline irrigation water or because of other physical constraints.

Management Aspect for Crop Production

Response of hydroponically grown gerbera to nutrient solution recycling and different nutrient cation ratios

Nitrogen (N) metabolism in plants requires adequate potassium (K) content in the cytoplasm. However, the influence of NH4 + in the nutrient solution on plant uptake of K is controversial. To identify the effect of N form on K uptake in sweet pepper (Capsicum annum L. cv. Hazera 1195) two hydroponic experiments containing three K concentrations (0.5, 2.5, and 5.0 mM) combined with four NH4 + −N to NO3 − −N mM ratios (0:6, 0.9:5.1, 1.8:4.2, or 3:3) at a constant total of 6 mM N were conducted during the spring-summer and autumn-winter seasons. Early fruit yield was affected by K concentration but not by N form. Replacing 0.9–1.8 mM (15–30%) of NO3 − −N by NH4 + −N increased total fruit yield, especially when only 0.5 mM K was supplied. No significant interaction of NH4 + −N and K concentration on early and total fruit yield was found in either season. The uptake rate of NH4 + −N was related to its concentration and was independent of K concentration in the culture solution. The uptake rate of K was reduced ...

S. Feigenbaum

Papers

Effect of potassium nitrate and ammonium nitrate on the growth, cation uptake and water requirement of tomato grown in sand culture