Abstract
Soybean (Glycine max [L.] Merr) is an important crop, as both food for humans and feed for livestock in Cambodia, but the yields are low, due to use of low yielding genotypes and limited use of inputs. This study aimed to investigate the effects of different genotypes and different N and P fertilizer sources on growth, seed yield, and seed protein of soybean. Five genotypes (Sbung, Hongry, 98C81, ACS1, and Kaiabi) were grown under different N (90 kg N ha−1 from urea, nano-n, Nitroplus, and without N application as control) and P fertilizers (50 kg P ha−1 from Inorganic P, nano-p, Mykovam, and without P application as control) in two screenhouse experiments. Shoot, root, and nodulation traits, as well as seed yield and protein, were significantly affected by genotypes and different N and/or P fertilizer sources. Notably, while genotypes Sbung and 98C81 showed the highest yields among the genotypes, regardless of different N and P fertilizers, only Sbung had the highest seed protein. The application of different N and/or P sources significantly increased seed yield, compared to non-N and -P application. Specifically, seed yield and seed protein were higher when treated with nano-n or urea, and number of nodules, root biomass, and nodule dry weight was increased with Nitroplus, whereas seed yield and protein were higher with nano-p, Mykovam, and inorganic P. Application rate of 90 kg N ha−1 and 50 kg P ha−1 produced higher seed yield and its components and seed protein. We conclude that N and P application as well as Nitroplus inoculation can help increase seed yield of soybean in Cambodia.
Highlights
The N source that showed the highest positive effects to days to flowering (DF) and stem biomass was urea, the effects of the other N sources (Nitroplus, nano-n) on shoot growth were greater than non-N application
The highest total aboveground biomass, leaf chlorophyll index, seed yield and seed protein were obtained under nano-n and urea, followed by Nitroplus conditions, applied with the same N rate (90 kg N ha−1 ), compared to non-N applied control
(50 kg ha−1 ) was produced under nano-p, Mykovam, and inorganic P, while seed protein was higher under nano-p and inorganic P conditions compared to Mykovam non-P applied conditions
Summary
Merrill) is one of the most important legume crops and essential source for high quality protein, edible oil, and micronutrients for human food and livestock feed around the world [1]. Soybean protein is rich in valuable amino acid lysine (5%), which is deficient in most of the cereals [2]. Like other legumes, fixes atmospheric nitrogen (N2 ), through association with gram-negative bacteria species of the genera Bradyrhizobium and Sinorhizobium [3]. The leguminous crop requirement of N is substantially fulfilled from symbiotic N2 fixation through Rhizobium, i.e., 120–150 kg N ha−1 [4]. Legumes leave about 30–40 kg N ha−1 for the Licensee MDPI, Basel, Switzerland
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