Iron Dense Biofortification In Rice (Oryza Sativa L.) Grains With Application Of High Efficient Foliar Iron Fertilizer And Regulation Of The Integrated Nutrient Management In Crop-Soil System

Iron (Fe) deficiency is widespread in the world, especially in developingcountries, where it is estimated that 40-45% of school-age children are anemic,approximately 50% of this anemia results from Fe deficiency. And in China, about20% of the people are influenced by Fe deficiency. Fe deficiency will weakenimmune function and impair growth and development. A major etiologic factor is thelow concentration of Fe from diets based on the staple cereals.Half of the world's population ate rice (Oryza sativa L.) daily and depended on itas their staple food. It provides 23%, which is more than wheat and corn, of all thecalories consumed by the world's population, and even provides 50-80% of theenergy intake of the people in the developing countries. Rice, however, is a poorsource of many essential micronutrients, especially of Fe for human nutrition.Malnutrition of Fe afflicts more than 50% of the world's population at present. Heavyand monotonous consumption of rice with low concentrations of Fe has beenconsidered a major reason. Therefore, even a slightly increase in its nutritive valuewould be highly profound for alleviation of malnutrition, and then would be greatbeneficial for human health.In several potential approaches discussed and processed to increase Feconcentration of rice grains, the fertilization via soils and foliar applications could bea more sustainable, low cost-effective and high efficient strategy. So in the paper, thedevelopment of a new high efficient Fe foliar fertilizer and its role on ironbiofortification in rice grians and also with regulation of intergrated nutrientmanagement in soil-crop system were discussed. The main results are summarized asfollows:Development of Fe(â…¡)-AA, a new high efficient Fe foliar fertilizer, for ironbiofortification of rice grians. With foliar spray of Fe(â…¡)-AA, iron dense in ricegrains will be enhanced significantly not less than 15% compared to foliar spray ofdeioned water, and other mineral nutrients in rice grains such as Ca, Mg, B, Zn, Cu,Mn are also increased markedly, and also protein and amino acids of rice areimproved. Compared to other iron fertilizer commonly adopted for foliar application,e. g. FeSO₄ 7H₂O and Fe(â…¢)-EDTA, the effectiveness of Fe(â…¡)-AA on ironbiofortification of rice grains together with improvement of rice nutritional qualtity ispreponderant. Fe²⁺ in Fe(â…¡)-AA is not as easily oxidated as FeSO₄ 7H₂O forchelation of Fe²⁺ with amino acids, and the price is less than Fe(â…¢)-EDTA, so it issuitable dominantly for field application.The effectiveness of Fe(â…¡)-AA on rice iron biofortification is stable. Withexperiments under pot and field conditions, iron biofortification of rice grains issignificant with treatment of foliar Fe(â…¡)-AA spray on different rice genotypescompared to foliar deioned water application. The most increase of rice iron dense ishappened on the indica rice numbered 429, which is enhanced by 67.41%. And on thejaponica rice 'Bing 98110', which is about 15%. Iron biofortification is more than 15% with treatment of foliar Fe(â…¡)-AA spray on the white sticky indica rice, andabout 38% on black sticky indica rice, and about 25% on non-sticky indiea rice.In the present study, compared to no Fe(â…¡)-AA foliar spray (CK), iron dense ofrice grains is biofortified significantly with foliar Fe(â…¡)-AA spray as well as grainyield in anthesis. For the japonica 'Bing 98110', grain yield is reached to 13.197 gplant^-1with foliar spray of Fe(â…¡)-AA in anthesis, which is increased significantly by13.96% compared to CK. And iron dense in polished rice is enhanced significantly by13.18%, also protein and amino acids in rice are improved notably by 13.78% and13.63% respectively. However, in tiller stage and grain-forming stage of rice, irondense can not be biofortified significantly with foliar Fe(â…¡)-AA spray.The rational intergrated nutrient management is one of important approaches toharvesting good nutritional quality and high grain yield on rice production. Under potconditions, the effects of N, P, K fertilization on rice iron biofortification is studied,and the relationship between them is established with the quadratic polynomialregression equation, Y=3.22+15.70X₁+14.62X₂-10.26X₁²-8.45X₂²-14.39X₁*X₂(R=0.86^*). High iron dense rice production would be guided on fertilization withthe simulation equation.Iron dense could be increased by N fertilization alone, and more ironconcentration could be obtained with more N application. Proper P supply couldincrease rice iron concentration, but P overfeeding would be adverse to iron dense inrice grains. Similarly, low K application could increase rice iron concentration, andhigh K fertilization would decrease iron concentration of rice grains.The absorption mechanism of Fe²⁺ and Fe³⁺ through foliar spray is studied. Theresults are shown that the activities of the plasma membrane redox system on leavesof the two rice varieties 'Zhenong 952' and 'Bing98110' are enhanced significantlywith foliar Fe^â…¢-EDTA spray, however, Fe^â…¡-EDTA has no effect on the redox system.The activities of the plasma membrane H⁺-ATPase on leaves of 'Zhenong 952'and 'Bing98110' are enhanced significantly with foliar Fe^â…¢-EDTA and Fe^â…¡-EDTAspray. That suggests leaf iron absorption is an active absorption process depended onthe plasma membrane H⁺-ATPase and redox system. Fe²⁺ is the main form absorbedby rice leaf, Fe³⁺ reduction is prerequisite before its aborption.Iron accumulation trend in rice grains on grain filling stage of rice crops is alsostudied. The results show that in anthesis when grain fill is ongoing the tendency ofiron concentration (mg Fe kg^-1 dry matter) in grains is down, first 20 days afteranthesis the downtrend is evident and then slow. Adverse to iron dense in grains, ironcontent (ug Fe grain^-1) in grains is up, first 20 days after anthesis the uptrend isevident and then slow. That suggests the speed of iron accumulation in grains per timeis lower markedly than downloads of the carbohydrate, but the content of iron pergrain is certainly increased slowly.Generally, iron concentration decreased initially even though their rate ofaccumulation was highest during this time. Iron accumulation and dry matter download in rice grains are not synchronous which show the machnism of iron andthe carbohydrate uptake by grains is different. The majority of uptake of iron and drymatter occurred within the first 20 days after anthesis which suggest if agronomicapproach, especially foliar iron fertilization, is intended to regulation on ironbiofortification of rice grains in rice production the optimum stage on rice cropsshould be first 20 days after anthesis.