Comparison of growth and nutrient uptake capacities of three dominant species of Qinhuangdao green tides

Since 2015, green tides have been blooming in offshore waters of Qinhuangdao, with serious impacts on the local ecological environment and tourism. Ulva australis, Bryopsis plumosa, and U. prolifera are the dominant species of Qinhuangdao green tides, following a sequential succession pattern. Ulva prolifera is the dominant species,with the highest biomass and the greatest influence on the local ecological environment. To study the reason of green tide dominant species succession and U. profilera became the dominant species with the largest biomass,we compared and analyzed the growth and nutrient uptake capacity of the three algae. The results showed that temperature significantly affects the growth of the three species. Within the temperature range of the experimental setup, the optimum temperature for the growth of U. australis, B. plumosa and U. profilera is10℃, 15℃, and 20–25℃, respectively. Combined with the temperature variation trend during green tide bloom development, we believe that temperature is the key environmental factor for the succession of the dominant species. Ulva prolifera has a higher growth rate than U. australis and B. plumosa under the same nitrate,ammonium, and phosphate levels. Significant differences in the maximum absorption rate(R_(max)) and R_(max)/Ks(the relationship between uptake rate and substrate concentration) values indicated that U. prolifera had an apparent competitive advantage over U. australis and B. plumosa regarding nutrient uptake. Therefore, the strong growth and nutrient uptake capacities of U. prolifera might be the main reason for becoming the dominant species with the largest biomass in Qinhuangdao green tides.

Effects of Controlled Release Nitrogen Fertilizer on Seedling Growth and Nutrient Uptake of Bitter Gourd

Different application rates of controlled release nitrogen fertilizer （CRFN） were designed to evaluate their effects on the growth and root morphology of bitter gourd （Momordica charantia L.） seedlings, and thus determine the optimal nitrogen amount and suitable nitrogen content in substrate at seedling transplanting,, in com- parison with conventional fertilizer application. CRFN was applied at five levels, 0, 0.6, 1.2, 2.4 and 4.8 kg N/m3, and conventional fertilizer was applied at 0.6 kg N/m3 as control. Four replicates were included in each treatment. The results showed that 0.6-2.4 kg N/m3 CRFN provided sufficient N nutrient for bitter gourd, with higher shoot and root dry weights, root length and root surface area than control treat- ments. Correspondingly, the total inorganic nitrogen in substrate ranged from 99.3 to 162.5 mg/pot at seedling transplanting in these treatments. 1.2 kg N/m3 was proven to be the optimal CRFN rate. Compared with conventional nitrogen fertilizer applica- tion, 1.2 kg N/m3 CRFN in substrate increased the dry weight, nitrogen uptake and improved root morphology indices of seedlings, and more than 83.3 mg/pot inorgan- ic nitrogen could be carried with substrate at transplanting, revealing a potential to reduce N-deficient risk after rain and basal N input by continuous release of CRFN.

Effects of different N sources on growth, nutrient uptake and ionic balance of Larlix gmelini seedlings

The effect of different sources and levels of N on dry matter production, nutrient uptake and ionic balance ofLarlix gmelini was studied. The results showed that the growth of the plants fertilized with ammonium was not as good as the control treatment. The growth of the plants fertilized with ammonium nitrate did not differ significantly from that in control or nitrate treatment, but was better than that in the ammonium treatment. Total cation concentrations in shoots varied little with N level in the ammonium and ammonium nitrate treatments, while those in the shoot increased with N level in the nitrate treatment. The treatments had little effect on the anion concentrations in the shoot. In the roots, the concentrations of both cations and anions changed little except for SO4 2? and Ca2+. There existed a higher carboxylate production in the plants fertilized with nitrate. The ratio between the production of carboxylate and the production of organic N Δ(C-A)/ΔNorg was constant with N supply in the plants receiving nitrate, but obviously declined with N supply for ammonium-fed plants. Δ (C-A)/ΔNorg values were intermediate between those of the nitrate and the ammonium-fed plants as for the mixed N source.

Effects of Nitrogen Application Level on Rice Nutrient Uptake and Ammonia Volatilization

The effects of different nitrogen application levels on nutrient uptake and ammonia volatilization were studied with the rice cultivar Zheyou 12 as a material.The accumulative amounts of nitrogen,phosphorus and potassium in rice plants across all growth stages showed a trend to increase with increasing nitrogen application levels from 0 to 270 kg/hm 2,but decreased at nitrogen application levels exceeding 270 kg/hm 2.Moreover,the accumulative uptake of nitrogen,phosphorus and potassium by the rice plants was increased by application of organic manure in combination with 150 kg/hm 2 nitrogen.The nitrogen uptake was high during the jointing to heading stages.Correlation analysis showed that rice yield was positively correlated with the accumulative uptake of nitrogen,phosphorus and potassium by the rice plants.The highest correlation coefficient observed was between the amount of nitrogen uptake and rice yield.The rate and accumulative amounts of ammonia volatilization increased with increasing nitrogen fertilizer application level.Compared with other stages,the rate and accumulative amount of ammonia volatilization were higher after base fertilizer application.The ammonia volatilization rates in response to the nitrogen application levels of 270 kg/hm 2 and 330 kg/hm 2 were much higher than those in the other treatments.The loss of nitrogen through ammonia volatilization accounted for 23.9% of the total applied nitrogen at the nitrogen application level of 330 kg/hm 2.

Nutrient deficiency limits population development,yield formation,and nutrient uptake of direct sown winter oilseed rape

Direct-sowing establishment method has great significance in improving winter oilseed rape（Brassica napus L.） production and guaranteeing edible oil security in China. However, nutrient responses on direct sown winter oilseed rape（DOR） performance and population development dynamic are still not well understood. Therefore, five on-farm experiments were conducted in the reaches of the Yangtze River（RYR） to determine the effects of nitrogen（N）, phosphorus（P）, and potassium（K） deficiencies on population density, dry matter production, nutrient uptake, seed yield, and yield components of DOR plants. Four fertilization treatments included the balanced NPK application treatment（NPK, 180 kg N, 39.3 kg P, 100 kg K, and 1.8 kg borax ha–1） and three nutrient deficiency treatments based on the NPK treatment, i.e., –N, –P, and –K. The results indicated that DOR population density declined gradually throughout the growing season, especially at over-wintering and pod-development stages. Nutrient deficiency decreased nutrient concentration in DOR plants, limited dry matter production and nutrient uptake, and thereby exacerbated density reduction during plants growth. The poor individual growth and reduced population density together decreased seed yield in the nutrient deficiency treatment. Averaged across all the experiments, seed yield reduced 61% by N deficiency, 38.3% by P deficiency, and 14.4% by K deficiency. The negative effects of nutrient deficiency on DOR performances followed the order of –N–P–K, and the effects were various among different nutrient deficiencies. Although N deficiency improved DOR emergence, but it seriously limited dry matter production and nutrient uptake, which in turn led to substantial plants death and therefore resulted in a very low harvested density. The P deficiency significantly reduced initial density, limited plants growth, and exacerbated density reduction. The K deficiency mainly decreased individual growth and yield, but did not affect density dynamic. Our results highlighted the importance of balanced NPK application in DOR production, suggesting that management strategy of these nutrients should be comprehensively considered with an aim to build an appropriate population structure with balanced plant density and individual growth.

Nutrient Uptake and Use Efficiency of Irrigated Rice in Response to Potassium Application

Potassium is one of the most important nutrients for rice production in many areas of Asia, especially in southeast China where potassium deficiency in soil is a widespread problem. Field experiments were conducted for four consecutive years in Jinhua City, Zhejiang Province, to determine utilization of nutrients (N, P and K) by inbred and hybrid rice and rice grain yields as affected by application of potassium fertilizer under irrigated conditions. Grain yield and nutrient harvest index showed a significant response to the NPK treatment as compared to the NP treatment. This suggested that potassium improved transfer of nitrogen and phosphorus from stems and leaves to panicles in rice plants. N and P use efficiencies of rice were not strongly responsive to potassium, but K use efficiency decreased significantly despite the fact that the amount of total K uptake increased. A significant difference between varieties was also observed with respect to nutrient uptake and use efficiency. Hybrid rice exhibited physiological advantage in N and P uptake and use efficiency over inbred rice. Analysis of annual dynamic change of exchangeable K and non-exchangeable K in the test soil indicated that non-exchangeable K was an important K source for rice. Potassium application caused an annual decrease in the concentration of available K in the soil tested, whereas an increase was observed in non-exchangeable K. It could be concluded that K fertilizer application at the rate of 100 kg ha-1 per season was not high enough to match K output, and efficient K management for rice must be based on the K input/output balance.

Effect of CO_2 Enrichment on the Growth and Nutrient Uptake of Tomato Seedlings

Exposing tomato seedlings to elevated CO2 concentrations may have potentially profound impacts on the tomato yield and quality. A growth chamber experiment was designed to estimate how different nutrient concentrations influenced the effect of elevated CO2 on the growth and nutrient uptake of tomato seedlings. Tomato (Hezuo 906) was grown in pots placed in controlled growth chambers and was subjected to ambient or elevated CO2 (360 or 720μL L-1) and four nutrient solutions of different strengths (1/2-, 1/4-, 1/8-, and 1/16-strength Japan Yamazaki nutrient solutions) in a completely randomized design. The results indicated that some agricultural characteristics of the tomato seedlings such as the plant height, stem thickness, total dry and fresh weights of the leaves, stems and roots, the G value (G value = total plant dry weight/seedling age), and the seedling vigor index (seedling vigor index = stem thickness/(plant height×total plant dry weight) increased with the elevated CO2, and the increases were strongly dependent on the nutrient solution concentrations, being greater with higher nutrient solution concentrations. The elevated CO2 did not alter the ratio of root to shoot. The total N, P, K, and C absorbed from all the solutions except P in the 1/8- and 1/16-strength nutrient solutions increased in the elevated CO2 treatment. These results demonstrate that the nutrient demands of the tomato seedlings increased at elevated CO2 concentrations.

Studies on nutrient uptake of rice and characteristics of soil microorganisms in a long-term fertilization experiments for irrigated rice

The ecosystem characteristics of soil microorganism and the nutrient uptake of irrigated rice were investigated in a split-block experiment with different fertilization treatments, including control (no fertilizer application), PK, NK, NP, NPK fertilization, in the main block, and conventional rice and hybrid rice comparison, in the sub block. Average data of five treatments in five years indicated that the indigenous N supply (INS) capacity ranged from 32.72 to 93.21 kg/ha; that indigenous P supply (IPS)capacity ranged from 7.42 to 32.25 kg/ha; and that indigenous K supply (IKS) capacity ranged from 16.24 to 140.51 kg/ha, which showed that soil available nutrient pool depletion might occur very fast and that P, K deficiency has become a constraint to increasing yields of consecutive crops grown without fertilizer application. It was found that soil nutrient deficiency and unbalanced fertilization to rice crop had negative effect on the diversity of the microbial community and total microbial biomass in the soil.The long-term fertilizer experiment (LTFE) also showed that balanced application of N, P and K promoted microbial biomass growth and improvement of community composition. Unbalanced fertilization reduced microbial N and increased C/N ratio of the microbial biomass. Compared with inbred rice, hybrid rice behavior is characterized by physiological advantage in nutrient uptake and lower internal K use efficiency.

Increasing photosynthetic performance and post-silking N uptake by moderate decreasing leaf source of maize under high planting density

To date,little attention has been paid to the effects of leaf source reduction on photosynthetic matter production,root function and post-silking N uptake characteristics at different planting densities.In a 2-year field experiment,Xianyu 335,a widely released hybrid in China,was planted at 60 000 plants ha^(–1 )(conventional planting density,CD) and 90 000 plants ha^(–1) (high planting density,HD),respectively.Until all the filaments protruded from the ear,at which point the plants were subjected to the removal of 1/2 (T1),1/3 (T2) and 1/4 (T3) each leaf length per plant,no leaf removal served as the control(CK).We evaluated the leaf source reduction on canopy photosynthetic matter production and N accumulation of different planting densities.Under CD,decreasing leaf source markedly decreased photosynthetic rate (P_(n)),effective quantum yield of photosystem II (ΦPSII) and the maximal efficiency of photosystem II photochemistry (F_(v)/F_(m)) at grain filling stage,reduced post-silking dry matter accumulation,harvest index (HI),and the yield.Compared with the CK,the 2-year average yields of T1,T2 and T3 treatments decreased by 35.4,23.8 and 8.3%,respectively.Meanwhile,decreasing leaf source reduced the root bleeding sap intensity,the content of soluble sugar in the bleeding sap,post-silking N uptake,and N accumulation in grain.The grain N accumulation in T1,T2 and T3 decreased by 26.7,16.5 and 12.8% compared with CK,respectively.Under HD,compared to other treatments,excising T3 markedly improved the leaf P_(n),ΦPSII and F_(v)/F_(m) at late-grain filling stage,increased the post-silking dry matter accumulation,HI and the grain yield.The yield of T3 was 9.2,35.7 and 20.1% higher than that of CK,T1 and T2 on average,respectively.The T3 treatment also increased the root bleeding sap intensity,the content of soluble sugar in the bleeding sap and post-silking N uptake and N accumulation in grain.Compared with CK,T1 and T2 treatments,the grain N accumulation in T3 increased by 13.1,40.9 and 25.2% on average,respectively.In addition,under the same source reduction treatment,the maize yield of HD was significantly higher than that of CD.Therefore,planting density should be increased in maize production for higher grain yield.Under HD,moderate decreasing leaf source improved photosynthetic performance and increased the post-silking dry matter accumulation and HI,and thus the grain yield.In addition,the improvement of photosynthetic performance improved the root function and promoted postsilking N uptake,which led to the increase of N accumulation in grain.

Effect of Potassium and Moisture on Rape Growth and Its Nutrient Uptake

The Interaction between potassium and moisture during the growth of and nutrient uptake by rapeseed plants grown on K-deficient soils has been investigated in this Study. The results show that the dry weight of the above-ground parts of the plant appears to be somewhat reduced when the volume water content of the soil remains 0.15 for 3 successive days. As the shortage in the soil water continues, the height of the plant root and the permeability of the root plasmalemma are markedly affected; the stem thickness and leaf area are reduced. However, K application can increase the dry matter weight of the above-ground parts, the thickness of the stem, and the area of the leaf. Application of K can also maintain a comparatively low water potential(ψ) and a comparatively high moisture content in the leaves, thus increasing the drought-resisting ability of the plant. When the volume water content of the soil is raised to 0.30, leaf yellowing as a symptom of nutrient deficiency appears on rapeseed plants grown on K-deficient soils. With increase in soil moisture content, the Ca concentration of the aerial parts of the rapeseed plant without K application increases while the K concentration decreases. Both K application and the soil moisture regime have very little effect on the Mg concentration in the plant. Under soil moisture stress, the nitrogen content and total amount of alnino acids in rape leaves increases; and thus more proline and glutamic acid is formed. On the other hand, the impact of soil moisture on plant's dry matter is governed by the status of potassium nutrition. On soils with low K, the moisture content has very little effect on yield; when K fertilizer is applied, however, the moisture content shows a very significant effect on yield increase.

Effect of K and Al on Growth and Nutrient Uptake of Rice

The effects of K and Al in K-deficient and complete nutrient solutions on the growth and nutrient uptake of rice were studied in the work. The effect of Al on the growth of roots and above-ground part of rice was associated with the concentration of Al in solution. A low level (0.1 mmol L-1) of Al promoted but a high level (1 mmol L-1) of Al inhibited the growth of both the root and the aerial part of rice, and the magnitude of K concentration in the nutrient solution also had an appreciable impact on this. Thus, in the low-Al solution, the plant treated with K2 (80 mg K L-1) produced much longer roots, showing the presence of interaction between Al and K; in the high-Al solution the K-treated plant had more and longer roots and a considerably greater dry weight of the above-ground pat compared with the plant deficient in K, showing the alleviating effect of K+ on Al toxicity.The mechanism of the Al-K interaction affecting the rice aerial part growth is not yet known, but part of the reason might be that the excessive amount of Al inhibited the uptake of some nutrients such as Ca and Mg and reduced their transfer to the plant aerial organs, whereas K showed its compensating effect on this; therefore, K could relieve Al toxicity at a high level of Al and promoted rice growth at a lOw level of Al.

Effect of Effluent from Biodigestion of Pre-Treated Rice Bran and Animal Manure on the Dry Matter Yield and Nutrient Uptake of <i>Amaranthus viridis</i>

The effect of effluents from biodigestion of pre-treated rice bran in combination with two types of animal manure on dry matter yield of Amarathus viridis was investigated using two pre-treatment methods: Soaking in ordinary distilled water and boiled in distilled water at 100°C. The pre-treated rice bran and animal manure were mixed (w/w basis) to give carbon to nitrogen ratio of 35:1 and 37:1 prior to loading into the digester to make eight different treatment combinations as follow: 1) Cow dung with no rice bran (NRB + CD);2) Raw rice bran + cow dung (RRB + CD);3) Soaked rice bran in ordinary distilled water + cow dung (SRB + CD);4) Boiled rice bran + cow dung (BRB + CD);5) Poultry manure with no rice bran (NRB + PM);6) Raw rice bran + poultry manure (RRB + PM);7) Soaked rice bran + poultry manure (SRB + PM);8) Boiled rice bran + poultry manure (BRB + PM). Samples of different treatment combinations were collected before digestion, both the samples and resultant effluents were subjected to elemental analysis using AAS. The effluents from the biodigestion of these combinations were applied at two rates (80 and 150 kg N ha-1) to 3 kg air-dried and sieved soil samples (0 - 20) cm in the greenhouse, control (0 kg N ha-1) and reference pot with NPK fertilizer at the 80 kg N ha-1 were arranged in a completely randomized design replicated three times. Amaranthus plants were introduced into each treated pot, left for four weeks before harvest, dry matter yields were recorded. Results of chemical analysis of raw materials and effluents obtained after biodigestion revealed the presence of all plant nutrients in both the raw materials and resultant effluents though the former had higher values in some nutrients than the effluent, for examples treatment combination of CD, the values for organic carbon (42.85%), Ca (3.41%) and Mg (0.61%) were higher than in the resultant effluent for CD, a similar trend was observed with other treatment combinations. Drastic reduction in heavy metal concentration was observed after digestion, Pb content in the raw materials for poultry manure reduced by 94.7% in the resultant effluent from BRB: PM thus making the effluent a better soil amendment. Raw chicken manure was richer in the nutrients needed for optimal crop growth however, raw cow dung had the highest. The amendment of effluent from boiled rice bran with poultry manure at 150 kg N ha-1 significantly increased the dry matter yield of Amaranthus viridis over control pots, NPK pots and all other amendments thus making it a good alternative to NPK fertilizer.

Determination of Nutrient Uptake Characteristic of Black Pepper （Piper nigrum L.）

The relationship between the growth and nutrient uptake by perennial crop such as pepper is poorly understood and improved understanding of such relationship is important for the establishment of rational crop management practices. In order to characterize the growth performance and quantify the nutrient removed, this study presents results of three consecutive cropping years, fertilized with 1, 2 and 3 ton ha1 of NPK fertilizer respectively. Plant biomass accumulated was evaluated every two months, separating plant into stems, branches, leaves, berries, fruit spikes and flowers. Total biomass of pepper increased linearly and reach maximum at 22 months after planting. Thereafter, a decrease in dry matter was observed due to fruit export and fallen leaves at harvest. However, at the 28 months of planting, the biomass of pepper vine showing some increasing trend indicating the vegetative growth was reassumed for the next flowering. At 30 months, the pepper had removed 293.08 kg of nitrogen, 46.41 kg of phosphorus, 264.95 kg of potassium, 35.4 kg of magnesium and 74.82 kg of calcium. Based on data obtained, the nutrient uptake rates were lower than nutrient applied suggested that fertilizer had been overused for pepper production. In light of these results obtained, the optimum fertilizer dosage would be 62-10-62-6-18 kg/ha, 237-22-246-22-65 kg/ha and 390-62-352-47-100 kg/ha of N-P-K-Mg-Ca for the year 1, year 2 and year 3 of cropping year.

Yield of Wheat (<i>Triticum aestivum</i>) and Nutrient Uptake in Grain and Straw as Influenced by Some Macro (S &Mg) and Micro (B &Zn) Nutrients

A wheat variety BARI Gom 26 was cultivated with an objective of evaluating the effects of macro/secondary nutrients as S and Mg, and micro nutrients as B and Zn on yield, yield contributing traits and nutrient uptake status by the crop. The field experiment was con-ducted in the “North Eastern Barind Tract Soils” at Kushadaha, Nawabganj, Dinajpur, Bangladesh from November, 2014 to March, 2015. The surface soil was clay in texture, having pH 5.61, organic matter 1.58%, total N 0.10%, available P 7.03 ppm, exchangeable K 0.11 meq/100g, available S 2.57 ppm, exchangeable Mg 0.55 meq/100g, available Zn 1.30 ppm, available B 0.08 ppm. The experiment was designed with five treatments laid out in a randomized complete block design (RCBD) with three replications. The treatments were T1: NPK (control), T2: NPK + S, T3: NPK + S + Mg, T4: NPK + S + Mg + Zn and T5: NPK + S + Mg + Zn + B. All plots of wheat received 100 kg N/ha, 30 kg P/ha and 70 kg K/ha as basal dose. The secondary and micro nutrients doses were 15 kg S/ha, 6 kg Mg/ha, 2.5 kg Zn/ha and 1.5 kg B/ha. Results revealed that the plant height, tillers/hill, 1000-grain weight, yield of grain and straw, uptake of some specific nutrients in grain and straw were signifi-cantly influenced by all the treatments, though these treatments did not show any identical effect on spike length, content of P and Mg in wheat. Significantly highest amount of 1000-grain weight, yield of grain and straw weight of wheat were obtained in applying T2 treatment that employed the addition of S with recommended dose of NPK. Significant positive effects were also observed for the rest parameters in receiving the treatments composed of secondary and micronutrients (T3, T4, and T5). The highest concentration of nutrient uptake N, P, K and S in grain and straw of wheat were also obtained due to the application of T2 treatment. In the case of Mg, the maximum uptake was recorded in T4 where Mg was added as a component of this treatment. In contrast, the highest content of Zn and B were extracted in receiving the treatment T5 both for grain and straw. However, results suggested that T2 treatment comprising recommended dose of NPK with S might be economic and suitable as for better production of 1000-grain weight, yield of grain and straw, uptake of N, P, K and S in grain and straw of wheat cultivated in the North Eastern Barind Tract Soils of Bangladesh under winter condition. The treatment T5 would also be recommended in the context of addition of micronutrients.

Effects of phosphorus on nutrient uptake and rhizosphere acidification of soybean (G/ycine max L.)

Pot experiment was conducted to examine how application of KH2PO4 （0-165 mg·kg^-1 P） to affect nutrient ion uptake and rhizosphere acidification of soybean （Glycine max L.） grown in greenhouse for 90 days. When supplied of 82 and 165 mg·kg^-1 P, soybeans showed excessive poison. Under all kinds of P levels, the K, Ca, Na and Mg concents in plant tissues were as below order K was nodules 〉 roots 〉 pods 〉 shoots; Ca was shoots 〉 roots 〉 nodules 〉 pods; Na was roots 〉 nodules 〉 pods 〉 shoots and Mg was shoots 〉 nodules 〉 roots 〉 pods. K concent in plant tisssues had greater effect on rhizosphere acidification than other cations in this experiment irrespective of P supply, and was significantly negative to pH. Na concentration was significantly positive to pH. Excessive P supply induced rhizosphere acidification, pH decreased as P supply increased from 82 to 165 mg·kg^-1. Ash alkalinity in shoots and roots was significantly positively correlated with rhizosphere pH irrespective of P supply. All these results suggested that P supply affected nutrient uptake, induced ash alkalinity to increase and rhizosphere pH to decrease in soybean.

Biomass,nutrient uptake and fatty acid composition of Chlamydomonas sp.ICE-L in response to different nitrogen sources

Nitrogen removal from media by microalgae provides the potential benefit of producing lipids for biodiesel and biomass. However, research is limited on algal growth and biomass under different nitrogen sources and provides little insight in terms of biofuel production. We studied the influences of nitrogen sources on cell growth and lipid accumulation of Chlamydomonas sp. ICE-L, one of a promising oil rich micro algal species. Chlamydomonas sp.ICE-L grown in NH_4 Cl medium had maximum growth rate. While the highest dry biomass of 0.28 g/L was obtained in media containing NH_4NO_3, the highest lipid content of 0.21 g/g was achieved under nitrogendeficiency condition with a dry biomass of 0.24 g/L. In terms of total polyunsaturated fatty acids（PUFAs）production, NH_4NO_3 and NH_4 Cl media performed better than nitrogen-deficiency and KNO_3 media.Furthermore, NH_4NO_3 and NH_4 Cl media elucidated better results on C18：3 and C20：5 productions while KNO_3and-N conditions were better in C16：0, C18：1 and C18：2, comparatively.

Effects of Silicon-Based Fertilizer on Growth, Yield and Nutrient Uptake of Rice in Tropical Zone of Vietnam

Application of silicon(Si) could greatly boost rice yield and mitigate abiotic stress,especially drought.A field experiment was conducted during 2015 at the research farm of Hong Duc University,Thanh Hoa City,Vietnam,to evaluate the effects of five different combined doses of standard fertilizer practice and Si fertilizer on growth,yield and yield components,as well as nutrient uptake of rice.The treatments consisted of the recommended dose of fertilizer(RDF,110 kg/hm^2 N + 90 kg/hm^2 P_2O_5 + 80 kg/hm^2 K_2O) as the control,RDF + 100 kg/hm^2 SiO_2,RDF + 200 kg/hm^2 SiO_2,RDF + 300 kg/hm^2 SiO_2 and RDF + 400 kg/hm^2 SiO_2.The results showed that the growth,grain and straw yields as well as yield components(number of grains per panicle,seed-setting rate and 1000-grain weight) were significantly affected by Si application.The highest grain yield of 3 705 kg/hm^2 was obtained with the highest level of Si fertilizer in combination with RDF(RDF + 400 kg/hm^2 SiO_2),however,it was statistically at par with the yields obtained with RDF + 300 kg/hm^2 SiO_2(3 664 kg/hm^2) and RDF + 200 kg/hm^2 SiO_2(3 621 kg/hm^2).The optimum dose of Si fertilizer with maximized grain yield(3 716 kg/hm^2) was 329 kg/hm^2 SiO_2.The nutrient(Si,N,P and K) uptakes of rice were also significantly enhanced by Si application.Si application at the level of 329 kg/hm^2 along with RDF would help in the sustainable production of rice in the tropical zone of Vietnam.

Effects of maize-soybean relay intercropping on crop nutrient uptake and soil bacterial community

Maize-soybean relay intercropping is an effective approach to improve the crop yield and nutrient use efficiency,which is widely practiced by farmers in southwest of China.To elucidate the characteristics of different planting patterns on crop nutrient uptake,soil chemical properties,and soil bacteria community in maize-soybean relay intercropping systems,we conducted a field experiment in 2015–2016 with single factor treatments,including monoculture maize(MM),monoculture soybean(MS),maize-soybean relay intercropping(IMS),and fallow(CK).The results showed that the N uptake of maize grain increased in IMS compared with MM.Compared with MS,the yield and uptake of N,P,and K of soybean grain were increased by 25.5,24.4,9.6,and 22.4%in IMS,respectively,while the N and K uptakes in soybean straw were decreased in IMS.The soil total nitrogen,available phosphorus,and soil organic matter contents were significantly higher in IMS than those of the corresponding monocultures and CK.Moreover,the soil protease,soil urease,and soil nitrate reductase activities in IMS were higher than those of the corresponding monocultures and CK.The phyla Proteobacteria,Acidobacteria,Chloroflexi,and Actinobacteria dominated in all treatments.Shannon’s index in IMS was higher than that of the corresponding monocultures and CK.The phylum Proteobacteria proportion was positively correlated with maize soil organic matter and soybean soil total nitrogen content,respectively.These results indicated that the belowground interactions increased the crop nutrient(N and P)uptake and soil bacterial community diversity,both of which contributed to improved soil nutrient management for legume-cereal relay intercropping systems.

Interaction effect of nitrogen form and planting density on plant growth and nutrient uptake in maize seedlings

High planting density is essential to increasing maize grain yield.However,single plants suffer from insufficient light under high planting density.Ammonium(NH_4^+)assimilation consumes less energy converted from radiation than nitrateIt is hypothesized that a mixed NO_3~–/NH_4^+supply is more important to improving plant growth and population productivity under high vs.low planting density.Maize plants were grown under hydroponic conditions at two planting densities(low density:only).A significant interaction effect was found between planting density and N form on plant biomass.Compared to nitrate only,75/25NO_3~–/NH_4^+increased per-plant biomass by 44%under low density,but by 81%under high density.Treatment with 75/25NO_3~–/NH_4^+increased plant ATP,photosynthetic rate,and carbon amount per plant by 31,7,and 44%under low density,respectively,but by 51,23,and 95%under high density.Accordingly,carbon level per plant under 75/25NO_3~–/NH_4^+was improved,which increased leaf area,specific leaf weight and total root length,especially for high planting density,increased by 57,17 and 63%,respectively.Furthermore,under low density,75/25NO_3~–/NH_4^+increased nitrogen uptake rate,while under high density,75/25NO_3~–/NH_4^+increased nitrogen,phosphorus,copper and iron uptake rates.By increasing energy use efficiency,an optimum NO_3~–/NH_4^+ratio can improve plant growth and nutrient uptake efficiency,especially under high planting density.In summary,an appropriate supply of NH_4^+in addition to nitrate can greatly improve plant growth and promote population productivity of maize under high planting density,and therefore a mixed N form is recommended for high-yielding maize management in the field.

Effects of Photosynthetically Active Radiation and Air Temperature on CO_2 Uptake of Pterocarpus macrocarpus in the Open Field

Since trees and plants can absorb CO2, forests are widely regarded as a carbon sink that may control the amount of CO2 in the atmosphere. The CO2 uptake rate of plants is affected by the plant species and environmental conditions such as photosynthetically active radiation (PAR), temperature, water and nutrient contents. PAR is the most immediate environmental control on photosynthesis while air temperature affects both photorespiration and dark respiration. In the natural condition, PAR and temperature play an important role in net CO2 uptake. The effects of PAR and air temperature on the CO2 uptake of Pterocarpus macrocarpus grown in a natural habitat were studied in the present work. Due to many uncontrollable factors, a simple rectangular hyperbola could not represent the measured data. The data were divided into groups of 2oC intervals; CO2 uptake in each group may then be related to PAR by a rectangular hyperbola function. Using the obtained functions, the effect of PAR was removed from the original data. The PAR-independent CO2 uptake was then related to air temperature. Finally, the effects of PAR (I) and air temperature (Ta) on the CO2 uptake rate (A) were combined as: (-0.0575Ta2+2.6691Ta-23.264)I A= ——————————————— (-0.00766Ta2+0.40666Ta-3.99924) (-4.8794Ta2+227.13Ta-2456.9)+I