Abstract An agronomically effective source of iron is provided in a plant nutrient solution as a soluble diferrate complex anion. The solution is effective for foliar application to plants and is compatible with plant nutrients commonly used for fertilization such as urea, ammonium nitrate and ammonium phosphate. If desired, water soluble salts of other trace metals can be added to the iron solution. Solutions containing the iron complexes have been observed to exhibit a greater agronomical effect on plants than exhibited by use of conventional iron sources such as aqueous solutions of water soluble iron salts or chelates of iron using conventional chelating agents. The solutions are also free of foliage or fruit spotting which frequently occurs with conventional iron sources. In a specific embodiment, a solution is provided which is effective for the foliar fertilization of pineapple and which contains a soluble ferric sulfatohydroxyl complex dissolved in ammonium nitrate or urea.
The solution of claim 1 in combination with from 0.05 to 10 weight percent of a halide or nitrate of manganese, zinc, molybdenum, magnesium or copper.
Claim 2
Dependent Claim
12 words
The solution of claim 1 wherein said iron source is metallic iron.
Claim 3
Dependent Claim
19 words
The solution of claim 1 in combination with 1 to about 60 weight percent P2O5, present as ammonium orthophosphate.
Claim 4
Dependent Claim
15 words
The solution of claim 1 in combination with 5 to about 70 weight percent urea.
Claim 5
Dependent Claim
80 words
An aqueous solution of from 0.05 to 15 weight percent iron present as the ammonium or alkali metal salt of a Mu -dihydroxo diferrate anion of the following formula: (Fe2(OH)2(SO4)3(H2O)5) 2 , or (Fe2(OH)3(SO4)2(H2O)5) 2 from 5 to about 35 weight percent nitrogen present as ammonium nitrate, ammonium phosphate or urea; and a sufficient quantity of an acid selected from the class consisting of nitric, phosphoric or hydrohalic to provide the pH of said solution between about 1 and 3.
Claim 6
Dependent Claim
28 words
The solution of claim 8 also containing from 1 to 60 weight percent P2O5 and wherein said nitrogen is present as a mixture of ammonium nitrate and phosphate.
Claim 7
Dependent Claim
11 words
The solution of claim 6 wherein said acid is nitric acid.
Claim 8
Dependent Claim
13 words
The solution of claim 8 wherein said ntirogen is present as ammonium nitrate.
Claim 9
Dependent Claim
18 words
The solution of claim 8 wherein said nitrogen is present as a mixture of urea and ammonium nitrate.