Rice yield nutrient uptake as affected by cyanobacteria soil amendments—a pot experiment

Abstract

Rice production and cyanobacterial N in acid soil can be improved by liming. There is evidence that the organic amendments can increase the soil pH. The aim of this study was to find appropriate combination of soil amendments and cyanobacteria capable for enhancing nutrient uptake and improving rice yield in acidic paddy soil. Three soil amendments (rice straw, sewage‐sludge composts, NPK) with and without inoculation of cyanobacteria were studied for rice plants (Oryza sativa L.) in a pot experiment. The sludge compost had significantly reduced soil acidity from 5.44 to 6.67. The plant N and K uptake increased significantly with sludge and cyanobacteria application. The yield components increased significantly with sludge, but decreased thereafter, an exception was the number of panicles, with straw compost. These characters were also significantly affected by inoculation with cyanobacteria except 100‐grain weight, filled‐grain percentage, and harvest index. The combination of sludge compost and cyanobacteria improved the yield components and consequently grain yield (138 g pot–1) compared with sludge treatment only (132 g pot–1). The amount of cyanobacterial N absorbed (N‐difference method) by rice plant under sludge compost was higher than that of soils amended with either rice straw or NPK treatments. Therefore, the addition of sewage sludge to acid paddy soil not only amended the soil properties but also activated the cyanobacteria and consequently improved rice plant nutrition and grain yield.

Effect of Nitrogen Sources on Microbial Biomass Nitrogen under Different Soil Types

“…Later, the microorganisms, soil biomass, are decomposed by other microbes, and then the nitrogen will be mineralized to ammonium followed by nitrification to nitrate. It has been observed that from the results in this experiment, the marked increase of the total N in soil under inoculated pot may be attributed not only to high population of microorganism and its activity but also to some of bacteria able to fix the atmospheric nitrogen which add additional nitrogen to the soil [8]. Clay soil had higher level of soil NH 4 than the loamy soil.…”

“…The soil samples were air-dried, ground and sieved using a 0.5 mm stainless sieve, and stored under laboratory condition until being analyzed. The total content of nitrogen and carbon in the soil and plant was determined using the Sumi-Graph CHN-21 analyzer at Tottori University Japan [8,24].…”

“…Nitrogen uptake in rice shoot was determined by multiplying the N concentration by shoot dry weight. The total amount of microbial N absorbed by rice plant was determined by N difference method at maximum tillering stage [8,[25][26][27][28]. Amount of microbial N was calculated from the difference between the extractable N from fresh soil and autoclaved soil samples under the same treatment as shown in the following equation.…”

“…Each group plays a role in the soil ecosystem and can assist the organic farmer in producing a healthy crop. Microorganisms can be grouped according to their function: free-living decomposers convert organic matter into nutrients for plants, and other microorganisms, rhizosphere organisms, are symbiotically associated with the plant roots and free-living nitrogen fixers [4][5][6][7][8]. Plant roots leak or exude a large number of organic substances and continually slough off root caps into the soil.…”

“…Bacteria benefit most from the food supplied in the rhizosphere and may form a continuous film around the root. Other micro-organisms liberate nutrients from the clay and humus colloids (a colloid is a mass of fine particles) [6,8].…”