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Upping zinc grain concentration, biochar for improved soil, increasing phosphate

By Nicola Cottam

- Last updated on GMT

Applying zinc fertilizer to wheat leaves is more effective in upping the zinc content of soils, find Chinese scientists
Applying zinc fertilizer to wheat leaves is more effective in upping the zinc content of soils, find Chinese scientists

Related tags Soil

Effects of foliar fertilization on grain zinc concentrations, biochar application can improve the nutrient profile of soils, and tapping into phosphate reserves with bio-fertilizers.

Increasing the bioavailability of zinc

Foliar zinc application is a more effective method for upping the zinc content of deficient soils, find scientists.

Chinese scientists conducted a two-year field and greenhouse study comparing the efficacy of soil and foliar (leaf) Zn fertilization to improve grain Zn concentration and bioavailability in wheat grown on potentially Zn-deficient calcareous soil.

Findings showed that although Zn application increased soil Zn by an average of 174% it had no significant effect on grain Zn concentration. In contrast, foliar Zn application increased grain Zn concentration by an average 61% and Zn bioavailability by an average of 36%.

Other findings revealed significant differences in grain phytic acid concentration among cultivars, which suggests Zn bioavailability may be improved using wheat cultivars with low phytic acid.

Zinc (Zn) deficiency affects one-third (or 73%) of the world’s population and is especially widespread in developing countries, primarily due to zinc deficient soils and the presence of phytic acid in grains, which can inhibit Zn absorption in plants.

Source: Journal of the Science of Food and Agriculture
Published: August 2014, DOI:10.1002/jsfa.6518
“Comparison of soil and foliar zinc application for enhancing grain zinc content of wheat when grown on potentially zinc-deficient calcareous soils”
Authors: Ai-qing Zhao, Xiao-hong Tian, Yu-xian Cao, Xin-chun Lu, Ting Liu


Effects of biochar on the nutrient content in arid soils

A combination of Conservation Farming (CF) and the application of low dosage biochar (charcoal plant matter in the soil) may significantly improve soil fertility and crop yields in tropical soils, according to new research.

Extensive farmer-led biochar trials is Zambia found a consistently positive response to the addition of biochar on maize grain yield. Adding 5% biochar to soils in Mongu, Kaoma and Kshui increased plant available water (PAW) by 10%, 17.6%, and 22.3%, respectively.

In Mongu, the addition of biochar significantly increased in situ​ plant-available potassium (K) and concentrations of K and phosphorus (P) in maize stover. Soil pH and cation exchange capacity (CEC) also increased.

Relative yield increases for maize were also noted in Mongu at the recommended fertilizer rates but not at reduced levels in groundnuts. This illustrates that biochar is probably most effective in combination with fertilization, as the CECs and soil pH propagate nutrient retention, the authors said.

Source: Journal of Plant Nutrition and Soil Science
Article first published online: August 12, 2014, DOI:10.1002/jpln.201300590
“Farmer-led maize biochar trials: Effect on crop yield and soil nutrients under conservation farming”
Authors: Vegard Martinsen, Jan Mulder, Victor Shitumbanuma, Magnus Sparrevik, Trond Børresen, Gerard Cornelissen


Bio-fertilizers can increase phosphate absorption

Inoculating wheat roots with bio-fertilizers such as phosphate (P) solubilising bacteria (PSB) and vesicular arbuscular mycorrhiza (VAM) can increase absorption of phosphate by approximately 4.6%, according to experts.

Root studies carried out over two years by scientists at the Indian Agricultural Research Institute ​(IARI) in New Delhi, investigated the individual and combined effects of PSB and VAM on root morphology, P in-flow rates and root cation exchange capacity (CEC or mineral absorption rates) of wheat and soybean crops.

PSB and VAMs are known to increase the level of phosphorus nutrients in crop plants, however there is limited information about the specific inter-relationship between the two bio-fertilizers and their impact on plant roots, the authors wrote.

Experiments showed that inoculation with PSB and VAM enhanced phosphate acquisition by increasing root CEC, root length density (RLD) and P in-flow rates, as well as root foraging and soil P mining capacity.

The compatibility of  P and VAM was attributed to the fact that vesicular arbuscular mycorrhiza mobilises soluble P and may increase the surface area of nutrient absorption from inaccessible areas. Similarly, VAM increases P uptake by improving root mobility and therefore accessibility to hard to reach nutrients.

Results suggest that 50% of recommended phosphate application can be substituted by inoculation with PSB and VAM to improve root absorption properties and productivity.

Source: Field Crops Research
Published online on June 26, 2014, DOI: 10.1016/j.fcr.2014.06.016
“Influence of phosphorus and biofertilizers on soybean and wheat root growth and properties”
Authors: Dibakar Mahanta​, Raj K. Rai​, Shiva Dhar Mishra​, Arunkumar Raja​, Tapan J. Purakayastha​, Eldho Varghese 

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