Impacts of soil fertility management on productivity and economics of rice and fodder intercropping systems under rainfed conditions in Odisha,India

Under small and marginal farm conditions, allocation of land exclusively for forages is not possible. Hence, integration of forages in existing crop geometry can ensure production of grain and fodder, simultaneously under rainfed conditions. A field experiment was conducted to study the effect of different nutrient management practices on rice and fodder intercropping systems under rainfed conditions during 2015–2017. The intercropping system comprised (i) sole rice (R), (ii) rice and cowpea (5:2) (CP) and (iii) rice and ricebean (5:2) (RB) whereas the different nutrient management practices comprised (i) application of farm yard manure (FYM) at 5 t ha^–1 (farmers’ practice) (N₁), (ii) application of inorganic fertilizer (recommended dose of fertilizer (RDF) of rice, 60:30:30 kg ha^–1 of N:P₂O₅:K₂O) (N₂) and (iii) application of both FYM at 5 t ha^–1 and 50% of RDF inorganic fertilizer (N₃). The results of the experiment revealed that the growth attribute such as leaf area was influenced significantly when fodder crops were taken as intercrops because rice plant was getting more nitrogen from soil due to nitrogen fixation of leguminous fodder crops. Among the nutrient management practices, significant differences in leaf area were found beween N₂ and N₁, and between N₃ and N₁ treatments. However, regarding total number of effective tillers, significant differences were found neither between nutrient management practices nor between cropping systems. The rice equivalent yield (REY) based on price (REY_P) was found to be significantly lower in CP (2 615 kg ha^–1; –6.4%) and RB intercropping systems (2 571 kg ha^–1; –8.0%) than in R monocropping system (2 794 kg ha^–1). However, the REY based on energy (REY_E) of CP (2 999 kg ha^–1; +7.3%) and RB (2 960 kg ha^–1; +5.9%) were found to be significantly higher than that of R (2 794 kg ha^–1) irrespective of nutrient management practices. Between different nutrient management practices, the N₃ treatment recorded the highest REY_P and REY_E which was at par with the N₂ treatment and significantly higher than the N₁ treatment irrespective of cropping systems. The combined application of both organic and inorganic sources of nutrients helped to supply nutrients throughout the growing season, which led to improved growth parameters and rice yield. The R monocropping system resulted in more income and rain water use efficiency (RWUE) closely followed by rice and fodder intercropping systems. However, the REY_E and energy use efficiency (EUE) of rice and fodder intercropping systems were higher than those of R. Also, fodder helped to meet the requirement of cattle feeding in the off-season. Hence, the intercropping system is advocated in the study zone. Further study can be done on ecosystem services and carbon sequestration potential of the intercropping system, as well as the system’s coping ability in response to short drought through observing periodic soil moisture regime in root zone.     

Effects of the potassium application rate on lipid synthesis and eating quality of two rice cultivars

Lipid content has an important effect on rice eating quality, but the effects of fertilizer application rate on the lipid synthesis and eating quality of rice are not well understood. Potassium (K) has a strong influence on rice quality and the requirement for K fertilizer in rice is greater than for nitrogen (N) and phosphorus (P) fertilizers. To investigate the effects of K fertilizer on the lipid synthesis and eating quality of rice, we used Nanjing 9108 (NJ9108, japonica) and IR72 (indica) rice as experimental materials and four K levels: K0 (0 kg ha^–1), K1 (90 kg ha^–1), K2 (135 kg ha^–1) and K3 (180 kg ha^–1). The results showed that the lipid content, free fatty acid (FFA) content, unsaturated fatty acid (UFA) content, malonyl-CoA (MCA) content, phosphatidic acid (PA) content, lipid synthesis-related enzyme activities and eating quality first increased and then decreased with increasing K in both cultivars. The maximum values were obtained under K2. However, the saturated fatty acid (SFA) content showed the opposite trend. No significant differences were found in pyruvate (PYR) content among the K treatments. The protein and oxaloacetic acid (OAA) contents and phosphoenolpyruvate carboxylase (PEPCase) activity of NJ9108 first decreased and then increased with increasing K, and the minimum values were obtained under K2; while IR72 showed the opposite trend and the maximum values were obtained under K1. Overall, increasing K optimized the fatty acid components and increased the lipid content and eating quality of rice by enhancing lipid synthesis-related enzyme activities and regulating substrate competition for lipid and protein synthesis. The optimal K application rate for lipid synthesis, eating quality and grain yield was 135 kg ha^–1 for both cultivars.     

Effects of mechanized deep placement of nitrogen fertilizer rate and type on rice yield and nitrogen use efficiency in Chuanxi Plain,China

This paper investigates the yield and nitrogen use efficiency (NUE) of machine-transplanted rice cultivated using mechanized deep placement of N fertilizer in the rice–wheat rotation region of Chuanxi Plain, China. It provides theoretical support for N-saving and improves quality and production efficiency of machine-transplanted rice. Using a single-factor complete randomized block design in field experiments in 2018 and 2019, seven N-fertilization treatments were applied, with the fertilizer being surface broadcast and/or mechanically placed beside the seedlings at (5.5±0.5) cm soil depth when transplanting. The treatments were: N0, no N fertilizer; U1, 180 kg N ha^–1 as urea, surface broadcast manually before transplanting; U2, 108 kg N ha^–1 as urea, surface broadcast manually before transplanting, and 72 kg N ha^–1 as urea surface broadcast manually on the 10th d after transplanting, which is not only the local common fertilization method, but also the reference treatment; UD, 180 kg N ha^–1 as urea, mechanically deep-placed when transplanting; M1, 81.6 kg N ha^–1 as urea and 38.4 kg N ha^–1 as controlled-release urea (CRU), mechanically deep-placed when transplanting; M2, 102 kg N ha^–1 as urea and 48 kg N ha^–1 as CRU, mechanically deep-placed when transplanting; M3, 122.4 kg N ha^–1 as urea and 57.6 kg N ha^–1 as CRU, mechanically deep-placed when transplanting. The effects of the N fertilizer treatments on rice yield and NUE were consistent in the 2 yr. With a N application rate of 180 kg ha^–1, compared with U2, the N recovery efficiency (NRE), N agronomic use efficiency (NAE) and yield under the UD treatment were 20.6, 3.5 and 1.1% higher in 2018, and 4.6, 1.7 and 1.2% higher in 2019, respectively. Compared with urea alone (U1, U2 or UD), the NRE, NAE and yield achieved by M3 (combined application of urea and controlled-release urea) were higher by 9.2–73.3%, 18.6–61.5% and 6.5–16.5% (2018), and 22.2–65.2%, 25.6–75.0% and 5.9–13.9% (2019), respectively. Compared with M3, the lower-N treatments M1 and M2 significantly increased NRE by 4.0–7.8% in 2018 and 3.1–4.3% in 2019, respectively. Compared with urea surface application (U1 or U2), the yield under the M2 treatment was higher by 4.3–12.9% in 2018 and 3.6–10.1% in 2019, respectively. Compared with U2, the NRE and NAE under the M2 treatment was higher by 36.9 and 36.3% in 2018, and 33.2 and 37.4% in 2019, mainly because of higher N uptake. There was no significant difference in the concentration of nitrate in the top 0–20 cm soil under U1, U2 and M2 treatments during the full heading and maturity stages. During the full heading stage, U2 produced the highest concentration of nitrite in 0–20 cm and 20–40 cm soil among the N fertilizer treatments. In conclusion, mechanized deep placement of mixed urea and controlled-release urea (M2) at transplanting is a highly-efficient cultivation technology that enables increased yield of machine-transplanted rice and improved NUE, while reducing the amount of N-fertilization applied.     

Improvement of soil fertility and rice yield after long-term application of cow manure combined with inorganic fertilizers

Fertilization is an effective technique to improve soil fertility and increase crop yield. The long-term effects of different fertilizers on soil considerably vary. Over 38 consecutive years of different fertilization positioning experiments in a double cropping rice field of Qiyang Red Soil Experimental Station, seven different fertilization treatments including CK (no fertilization), NPK (nitrogen, phosphorus, and potassium fertilizer), M (cow manure), NPKM (nitrogen, phosphorus, and potassium with cow manure), NPM (nitrogen and phosphorus with cow manure), NKM (nitrogen and potassium with cow manure), and PKM (phosphorus and potassium with cow manure) were applied to study the effects on rice yield, soil fertility, and nutrient apparent balance in a paddy field. The results showed that the annual average yields of rice in NPKM, NPM, NKM, PKM, M, NPK and CK treatments ranged from 6 214 to 11 562 kg ha^–1. Yields under long-term organic and inorganic treatments (NPKM, NPM, NKM and PKM) were 22.58, 15.35, 10.53 and 4.41%, respectively, greater than under the NPK treatment. Soil organic carbon (SOC), total nitrogen (TN), available nitrogen (AN) and available potassium (AK) concentration with long-term organic and inorganic treatment (NPKM, NPM, NKM and PKM) were significantly higher than in inorganic fertilizer (NPK) treatments. Soil total phosphorus (TP) and available phosphorus (AP) contentration with organic fertilizer combined with inorganic N and P fertilizer treatment (NPKM, NPM and PKM) were significantly higher than with inorganic fertilizer alone (NPK treatments). The average annual rice yield (11 562 kg ha^–1), SOC (20.88 g kg^–1), TN (2.30 g kg^–1), TP (0.95 g kg^–1), TK (22.50 g kg^–1) and AP (38.94 mg kg^–1) concentrations were the highest in the NPKM treatment. The soil AN concentration (152.40 mg kg^–1) and AK contentration (151.00 mg kg^–1) were the highest in the NKM treatment. N and P application led to a surplus of nitrogen and phosphorus in the soil, but NPKM treatment effectively reduced the surplus compared with other treatments. Soils under all treatments were deficient in potassium. Correlation analysis showed that SOC, TN, AN, TP, and AP contentration was significantly correlated with rice yield; the correlation coefficients were 0.428, 0.496, 0.518, 0.501, and 0.438, respectively. This study showed that the combined application of N, P, and K with cow manure had important effects on rice yield and soil fertility, but balanced application of N, P, and K with cow manure was required.     

Closing the nitrogen use efficiency gap and reducing the environmental impact of wheat-maize cropping on smallholder farms in the Guanzhong Plain,Northwest China

A high crop yield with the minimum possible cost to the environment is generally desirable. However, the complicated relationships among crop production, nitrogen (N) use efficiency and environmental impacts must be clearly assessed. We conducted a series of on-farm N application rate experiments to establish the linkage between crop yield and N₂O emissions in the Guanzhong Plain in Northwest China. We also examined crop yield, partial factor productivity of applied N (PFPN) and reactive N (Nr) losses through a survey of 1 529 and 1 497 smallholder farms that grow wheat and maize, respectively, in the region. The optimum N rates were 175 and 214 kg ha^–1 for winter wheat and summer maize, respectively, thereby achieving the yields of 6 799 and 7 518 kg ha^–1, correspondingly, with low N₂O emissions based on on-farm N rate experiments. Among the smallholder farms, the average N application rates were 215 and 294 kg ha^–1 season^–1, thus producing 6 490 and 6 220 kg ha^–1 of wheat and maize, respectively. The corresponding PFPN values for the two crops were 36.8 and 21.2 kg N kg^–1, and the total N₂O emissions were 1.50 and 3.88 kg ha^–1, respectively. High N balance, large Nr losses and elevated N₂O emissions could be explained by the overdoses of N application and low grain yields under the current farming practice. The crop yields, N application rates, PFPN and total N₂O for wheat and maize were 18 and 24% higher, 42 and 37% less, 75 and 116% higher, and 42 and 47% less, correspondingly, in the high-yield and high-PFPN group than in the average smallholder farms. In conclusion, closing the PFPN gap between the current average and the value for the high-yield and high-PFPN group would increase crop production and reduce Nr losses or the total N₂O emissions for the investigated cropping system in Northwest China.     

Yield performance and optimal nitrogen and phosphorus application rates in wheat and faba bean intercropping

Yield performance in cereal and legume intercropping is related to nutrient management, however, the yield response of companion crops to nitrogen (N) input is inconclusive and only limited efforts have focused on rationed phosphorous (P) fertilization. In this study, two multi-year field experiments were implemented from 2014–2019 under identical conditions. Two factors in a randomized complete block design were adopted in both experiments. In field experiment 1, the two factors included three planting patterns (mono-cropped wheat (MW), mono-cropped faba bean (MF), and wheat and faba bean intercropping (W//F)) and four N application rates (N0, 0 kg N ha^–1; N1, 90 and 45 kg N ha^–1 for wheat and faba beans, respectively; N2, 180 and 90 kg N ha^–1 for wheat and faba beans, respectively; and N3, 270 and 135 kg N ha^–1 for wheat and faba beans, respectively). In field experiment 2, the two factors included three P application rates (P0, 0 kg P₂O₅ ha^–1; P1, 45 kg P₂O₅ ha^–1; and P2, 90 kg P₂O₅ ha^–1) and the same three planting patterns (MW, MF, and W//F). The yield performances of inter- and mono-cropped wheat and faba beans under different N and P application rates were analyzed and the optimal N and P rates for intercropped wheat (IW) and MW were estimated. The results revealed that intercropping favored wheat yield and was adverse to faba bean yield. Wheat yield increased by 18–26%, but faba bean yield decreased by 5–21% in W//F compared to MW and MF, respectively. The stimulated IW yield drove the yield advantage in W//F with an average land equivalent ratio (LER) of 1.12. N and P fertilization benefited IW yield, but reduced intercropped faba bean (IF) yield. Nevertheless, the partial LER of wheat (pLER_wheat) decreased with increasing N application rates, and the partial LER of faba bean (pLER_{faba bean}) decreased with increasing P application rates. Thus, LER decreased as N input increased and tended to decline as P rates increased. IW maintained a similar yield as MW, even under reduced 40–50% N fertilizer and 30–40% P fertilizer conditions. The estimated optimum N application rates for IW and MW were 150 and 168 kg ha^–1, respectively, and 63 and 62 kg ha^–1 for P₂O₅, respectively. In conclusion, W//F exhibited yield advantages due to stimulated IW yield, but the intercropping yield benefit decreased as N and P inputs increased. Thus, it was concluded that modulated N and P rates could maximize the economic and ecological functions of intercropping. Based on the results, rates of 150 kg Nha^–1 and 60 kg P₂O₅ ha^–1 are recommended for IW production in southwestern China and places with similar conditions.     

Effects of reduced nitrogen and suitable soil moisture on wheat(Triticum aestivum L.) rhizosphere soil microbiological,biochemical properties and yield in the Huanghuai Plain,China

Soil management practices affect rhizosphere microorganisms and enzyme activities, which in turn influence soil ecosystem processes. The objective of this study was to explore the effects of different nitrogen application rates on wheat(Triticum aestivum L.) rhizosphere soil microorganisms and enzyme activities, and their temporal variations in relation to soil fertility under supplemental irrigation conditions in a fluvo-aquic region. For this, we established a split-plot experiment for two consecutive years(2014–2015 and 2015–2016) in the field with three levels of soil moisture: water deficit to no irrigation(W1), medium irrigation to(70±5)% of soil relative moisture after jointing stage(W2), and adequate irrigation to(80±5)% of soil relative moisture after jointing stage(W3); and three levels of nitrogen: 0 kg ha~(–1)(N1), 195 kg ha~(–1)(N2) and 270 kg ha~(–1)(N3). Results showed that irrigation and nitrogen application significantly increased rhizosphere microorganisms and enzyme activities. Soil microbiological properties showed different trends in response to N level; the highest values of bacteria, protease, catalase and phosphatase appeared in N2, while the highest levels of actinobacteria, fungi and urease were observed in N3. In addition, these items performed best under medium irrigation(W2) relative to W1 and W3; particularly the maximum microorganism(bacteria, actinobacteria and fungi) amounts appeared at W2, 5.37×10~7 and 6.35×10~7 CFUs g–1 higher than those at W3 in 2014–2015 and 2015–2016, respectively; and these changes were similar in both growing seasons. Microbe-related parameters fluctuated over time but their seasonality did not hamper the irrigation and fertilization-induced effects. Further, the highest grain yields of 13 309.2 and 12 885.7 kg ha~(–1) were both obtained at W2 N2 in 2014–2015 and 2015–2016, respectively. The selected properties, soil microorganisms and enzymes, were significantly correlated with wheat yield and proved to be valuable indicators of soil quality. These results clearly demonstrated that the combined treatment(W2 N2) significantly improved soil microbiological properties, soil fertility and wheat yield on the Huanghuai Plain, China.     

Effects of nitrogen application rates and irrigation regimes on grain yield and water use efficiency of maize under alternate partial root-zone irrigation

Faced with the scarcity of water resources and irrational fertilizer use, it is critical to supply plants with water and fertilizer in a coordinated pattern to improve yield with high water use efficiency (WUE). One such method, alternate partial root-zone irrigation (APRI), has been practiced worldwide, but there is limited information on the performance of different irrigation regimes and nitrogen (N) rates under APRI. The objectives of this study were to investigate the effects of varying irrigation regimes and N rates on shoot growth, grain yield and WUE of maize (Zea mays L.) grown under APRI in the Hexi Corridor area of Northwest China in 2014 and 2015. The three N rates were 100, 200 and 300 kg N ha⁻¹, designated N₁, N₂ and N₃, respectively. The three irrigation regimes of 45–50%, 60–65% and 75–80% field capacity (FC) throughout the maize growing season, designated W₁, W₂ and W₃, respectively, were applied in combination with each N rate. The results showed that W₂ and W₃ significantly increased the plant height, stem diameter, crop growth rate, chlorophyll SPAD value, net photosynthetic rate (P_n), biomass, grain yield, ears per ha, kernels per cob, 1 000-kernel weight, harvest index, evapotranspiration and leaf area index (LAI) compared to W₁ at each N rate. The N₂ and N₃ treatments increased those parameters compared to N₁ in each irrigation treatment. Increasing the N rate from the N₂ to N₃ resulted in increased biomass and grain yield under W₃ while it had no impact on those under the W₁ and W₂ treatments. The W₃N₃ and W₂N₂ and W₂N₃ treatments achieved the greatest and the second-greatest biomass and grain yield, respectively. Increasing the N rate significantly enhanced the maximum LAI (LAI at the silking stage) and P_n under W₃, suggesting that the interaction of irrigation and fertilizer N management can effectively improve leaf growth and development, and consequently provide high biomass and grain yield of maize. The W₂N₂, W₂N₃ and W₃N₃ treatments attained the greatest WUE among all the treatments. Thus, either 60–65% FC coupled with 200–300 kg N ha⁻¹ or 75–80% FC coupled with 300 kg N ha⁻¹ is proposed as a better pattern of irrigation and nitrogen application with positive regulative effects on grain yield and WUE of maize under APRI in the Hexi Corridor area of Northwest China and other regions with similar environments. These results can provide a basis for in-depth understanding of the mechanisms of grain yield and WUE to supply levels of water and nitrogen.     

Effect of low-nitrogen stress on photosynthesis and chlorophyll fluorescence characteristics of maize cultivars with different low-nitrogen tolerances

Nitrogen(N) is a critical element for plant growth and productivity that influences photosynthesis and chlorophyll fluorescence. We investigated the effect of low-N stress on leaf photosynthesis and chlorophyll fluorescence characteristics of maize cultivars with difference in tolerance to low N levels. The low-N tolerant cultivar ZH311 and low-N sensitive cultivar XY508 were used as the test materials. A field experiment(with three N levels: N0, 0 kg ha–1; N1, 150 kg ha–1; N2, 300 kg ha–1) in Jiyanyang, Sichuan Province, China, and a hydroponic experiment(with two N levels: CK, 4 mmol L–1; LN, 0.04 mmol L–1) in Chengdu, Sichuan Province, China were conducted. Low-N stress significantly decreased chlorophyll content and rapid light response curves of the maximum fluorescence under light(Fm′), fluorescence instable state(Fs), non-photochemical quenching(qN), the maximum efficiency of PSII photochemistry under dark-adaption(Fv/Fm), potential activity of PSII(Fv/Fo), and actual photochemical efficiency of PSII(ΦPSII) of leaves. Further, it increased the chlorophyll(Chl) a/Chl b values and so on. The light compensation point of ZH311 decreased, while that of XY508 increased. The degree of variation of these indices in low-N tolerant cultivars was lower than that in low-N sensitive cultivars, especially at the seedling stage. Maize could increase Chl a/Chl b, apparent quantum yield and light saturation point to adapt to N stress. Compared to low-N sensitive cultivars, low-N tolerant cultivars maintained a higher net photosynthetic rate and electron transport rate to maintain stronger PSII activity, which further promoted the ability to harvest and transfer light. This might be a photosynthetic mechanism by which low-N tolerant cultivar adapt to low-N stress.     

Effects of salt and nitrogen on physiological indices and carbon isotope discrimination of wheat cultivars in the northeast of Iran

In order to study the effects of different levels of salt stress and nitrogen(N) on physiological mechanisms,carbon isotope discrimination(△~(13)C),and yield of two wheat cultivars(cv.),a two-year field experiment was carried out during 2013-2015.The treatments included three levels of salt stress(1.3,5.2,and 10.5 dS m~(-1)),three levels of N(50,100,and 150 kg N ha~(-1)),and two wheat cultivars,Bam and Toos.Under salt stress,N application(100 and 150 kg N ha~(-1)) produced a significant effect on both cultivars with respect to physiological traits,i.e.,net photosynthetic rate(P_n),stomatal conductance(g_s),chlorophyll index(Cl),Na~+/K~+ratio as well as the grain yield(GY).The salt-tolerant and-sensitive cultivars exhibited the maximum values of physio-biochemical and yield attributes at 100 and 150 kg N ha~(-1),respectively.The results of △~(13)C showed a significant difference(P0.001) between wheat cultivars under the control and salt stress.According to our result,salt-tolerant cultivar Bam seems to be more efficient in terms of higher GY,P_n,g_s,Cl,and lower Na~+/K~+ratio as well as higher △~(13)C as compared with salt-sensitive cultivar Toos,under salt stress.Therefore,a significant positive correlation that observed between △~(13)C and GY,indicated that △~(13)C may be an effective index for indirect selection of yield potential in wheat under irrigation regimes with saline water.     

Effects of nitrogen fertilizer and chemical regulation on spring maize lodging characteristics,grain filling and yield formation under high planting density in Heilongjiang Province,China

Now,lodging is a major constraint factor contributing to yield loss of maize (Zea mays L.) under high planting density.Chemical regulation and nitrogen fertilizer could effectively coordinate the relationship between stem lodging and maize yield,which significantly reduce lodging and improve the grain yield.The purpose of this study was to explore the effects of chemical regulation and different nitrogen application rates on lodging characteristics,grain filling and yield of maize under high density.For this,we established a field study during 2017 and 2018 growing seasons,with three nitrogen levels of N100 (100 kg ha~(–1)),N200 (200 kg ha~(–1)) and N300 (300 kg ha~(–1)) at high planting density (90 000 plants ha~(–1)),and applied plant growth regulator (Yuhuangjin,the mixture of 3% DTA-6 and 27% ethephon) at the 7th leaf.The results showed that chemical control increased the activities of phenylalanine ammonia-lyase (PAL),tyrosine ammonia-lyase (TAL),4-coumarate:Co A ligase (4CL),and cinnamyl alcohol dehydrogenase (CAD),and increased the lignin,cellulose and hemicellulose contents at the bottom of the 3rd internode,which significantly reduced the lodging percentage.The lignin-related enzyme activities,lignin,cellulose and hemicellulose contents decreased with the increase of nitrogen fertilizer,which significantly increased the lodging percentage.The 200 kg ha~(–1) nitrogen application and chemical control increased the number,diameter,angle,volume,and dry weight of brace roots.The 200 kg ha~(–1) nitrogen application and chemical control significantly increased the activities of ADP-glucose pyrophosphorylase (AGPase),soluble starch synthase (SSS) and starch branching enzyme(SBE),which promoted the starch accumulation in grains.Additional,improved the maximum grain filling rate (V_(max)) and mean grain filling rate (V_m),which promoted the grain filling process,significantly increased grain weight and grain number per ear,thus increased the final yield.     

Combining rhizosphere and soil-based P management decreases the P fertilizer demand of China by more than half based on LePA model simulations

Phosphorus (P) is a finite natural resource and is increasingly considered to be a challenge for global sustainability. Agriculture in China plays a key role in global sustainable P management. Rhizosphere and soil-based P management are necessary for improving P-use efficiency and crop productivity in intensive agriculture in China. A previous study has shown that the future demand for phosphate fertilizer by China estimated by the LePA model (legacy phosphorus assessment model) can be greatly reduced by soil-based P management (the building-up and maintenance approach). The present study used the LePA model to predict the phosphate demand by China through combined rhizosphere and soil-based P management at county scale under four P fertilizer scenarios: (1) same P application rate as in 2012; (2) rate maintained same as 2012 in low-P counties or no P fertilizer applied in high-P counties until targeted soil Olsen-P (TP_Olsen) level is reached, and then rate was the same as P-removed at harvest; (3) rate in each county decreased to 1–7 kg ha^–1 yr^–1 after TP_Olsen is reached in low-P counties, then increased by 0.1–9 kg ha^–1 yr^–1 until equal to P-removal; (4) rate maintained same as 2012 in low-P counties until TP_Olsen is reached and then equaled to P-removal, while the rate in high-P counties is decreased to 1–7 kg ha^–1 yr^–1 until TP_Olsen is reached and then increased by 0.1–9 kg ha^–1 yr^–1 until equal to P-removal. Our predictions showed that the total demand for P fertilizer by whole China was 693 Mt P₂O₅ and according to scenario 4, P fertilizer could be reduced by 57.5% compared with farmer current practice, during the period 2013–2080. The model showed that rhizosphere P management led to a further 8.0% decrease in P fertilizer use compared with soil-based P management. The average soil Olsen-P level in China only needs to be maintained at 17 mg kg^–1 to achieve high crop yields. Our results provide a firm basis for government to issue-relevant policies for sustainable P management in China.     

Organic and inorganic fertilization influenced on yield and quality of sugar beet genotypes

The objective of this study was to evaluate the effects of organic and inorganic fertilizers on yield and quality of sugar beet genotypes (Beta vulgaris L.). Therefore a field trial was carried out at New Developmental Farm of The University Agriculture, Peshawar, Pakistan during winter 2012–13. The field experiment was layout in randomized complete block design with split plot arrangement having three replications. Fertilizers treatments (control, higo organic plus (composted manure, it contains N 2%, P 3%, K 3%, organic matter 40%, organic carbon 11%, Zn 145 mg kg^–1, Cu 56 mg kg^–1, Fe 380 mg kg^–1 and Mg 228 mg kg^–1), maxicrop sea gold (extract of sea weeds i.e., Sargasssum, Laminara Polysaccharide and Ascophyllum Nodosum), farm yard manure, NP (90: 60 kg ha^–1), NP (120: 90 kg ha^–1) and NP (150: 120 kg ha^–1) were allotted to main plots while genotypes (Sandrina, Serenada and Kawe Terma) to the sub plots. Farm yard manure (10 t ha^–1) and higo organic Plus (5 t ha^–1) was incorporated in the soil before seed bed preparation. Maxicrop sea gold (5 lit ha^–1) was sprayed after the emergence of the crop. All phosphorus was applied @ of 60, 90 and 120 kg ha^–1 at the time of sowing while nitrogen @ of 90, 120 and 150 kg ha^–1 in two splits/3 of the dose was applied at the time of sowing while the remaing 1/3 of the dose was applied before earthen up. Plots treated with application of NP ratio 120: 90 kg ha^–1 produced maximum beet yield (76.4 t ha^–1), sugar yield (11.1 t ha^–1), Pol (polarizable sugar) percentage (14.67%) and more economic return (Rs.234 Thousand ha^–1) as compared to control plots. Sugar beet genotype Serenada had significantly produced maximum beet yield (55.5 t ha^–1), sugar yield (7.9 t ha^–1), pol (polarizable sugar) percentage (14.60%), brix percentage (14.60%) and more economic return (158) as compared to other genotypes. It was concluded from the above results that sugar beet genotype Serenada treated with NP ratio 120: 90 kg ha^–1 for improved sugar beet productivity and quality therefore it is recommended for general practice in agro-climatic conditions of Peshawar valley.     

土壤肥力对红壤性水稻土水稻产量和氮肥利用效率的影响

【目的】土壤肥力是红壤性稻田水稻丰产的基础。明确不同肥力对红壤性水稻土作物产量和氮肥利用效率的影响,为红壤性稻田土壤培肥和合理施肥提供科学依据。【方法】选取质地相似的不同肥力水平的红壤性水稻土进行盆栽试验(以土壤有机质的高低代表土壤肥力的高低),利用~(15)N同位素示踪技术研究不同肥力水平(F_L、F_M和F_H分别代表低肥力、中肥力和高肥力,其低、中、高肥力土壤的有机质含量分别为19.9、29.6、38.9 g·kg~(-1))和氮肥水平(N_0、N_(150)和N_(225)分别代表施氮量为0、150和225 kg·hm~(-2),共9个试验处理,分别为F_LN_0、F_LN_(150)、F_LN_(225)、F_MN_0、F_MN_(150)、F_MN_(225)、F_HN_0、F_HN_(150)和F_HN_(225))对水稻产量及其构成、氮肥吸收及其去向的影响。【结果】提升土壤肥力和施氮均能显著提高水稻的有效穗数、产量和总吸氮量。与N_0相比,F_L、F_M和F_H在N_(150)处理下的增产率分别为63%、40%、17%,而在N_(225)处理下的增产率分别为89%、55%和23%。在中、低肥力土壤上,增施氮肥能显著提高水稻产量,而F_HN_(150)和F_HN_(225)处理之间产量无显著差异。~(15)N示踪结果表明,相同施氮量条件下,水稻植株对肥料氮素和土壤氮素的吸收量均随土壤肥力的提高而增加。但是,水稻植株总吸氮量中来自土壤氮素的比例随土壤肥力的提高而增加,而来自肥料氮素的比例则随之降低。增施氮肥会增加水稻吸收肥料氮素的比例,降低其吸收土壤氮素的比例。F_L、F_M和F_H土壤水稻的平均氮肥回收率分别为42%、48%和52%,平均氮肥残留率分别为20%、23%和28%,平均氮肥损失率分别为38%、29%和20%。F_LN_(225)氮肥回收率显著高于F_LN_(150),F_M两个施氮量氮肥回收率无显著差异,而F_HN_(225)的氮肥回收率显著低于F_HN_(150)。提升土壤肥力能显著提高土壤微生物量氮、铵态氮和固定态铵的含量。【结论】提升土壤肥力能显著提高红壤性水稻土的水稻产量以及化肥氮的回收率和残留率,而降低氮肥损失率。在低肥力土壤上适当增加施氮量有利于增加产量和氮肥回收率;而在高肥力土壤上适当降低施氮量在保证较高水稻产量的同时,能够提高氮肥回收率、降低氮肥损失。     

Estimation of economic and environmental potentials of variable rate versus uniform N fertilizer application to spring barley on morainic soils in SE Norway

Spring barley was grown for 4 years (2001–2004) in field trials at two sites on morainic soil in central SE Norway, with five N level treatments: 0, 60, 90, 120 and 150 kg N ha^-1. Regression analyses showed that a selection of soil properties could explain 95–98% of the spatial yield variation and 47–90% of the yield responses (averaged over years). A strategy with uniform fertilizer application of 120 kg N ha⁻¹ (U _N120) was compared with two variable-rate (VR) strategies, with a maximum N rate of either 150 kg N ha⁻¹ (VR_N150) or 180 kg N ha⁻¹ (VR_N180). These strategies were tested using either Norwegian prices (low price ratio of N fertilizer to yield value; P_N/P_Y), or Swedish prices (high P_N/P_Y). The VR_N180 strategy had the highest potential yield and net revenue (yield value minus N cost) at both sites and under both price regimes. Using this strategy with Norwegian prices would increase the profit of barley cropping as long as at least 40 and 31% of the estimated potential increase in net revenue was realized, respectively. Using Swedish prices, uniform application appeared to be as good as or even better economically than the VR methods, when correcting for extra costs of VR application. The environmental effect of VR compared with uniform application, expressed as N not accounted for, showed contrasting effects when using Norwegian prices, but was clearly favourable using Swedish prices, with up to 20% reduction in the amount of N not accounted for.     

Nitrogen Nutrition Index and Its Relationship with N Use Efficiency,Tuber Yield,Radiation Use Efficiency,and Leaf Parameters in Potatoes

Knowledge about crop growth processes in relation to N limitation is necessary to optimize N management in farming system. Plant-based diagnostic method, for instance nitrogen nutrition index (NNI) were used to determine the crop nitrogen status. This study determines the relationship of NNI with agronomic nitrogen use efficiency (AE_N), tuber yield, radiation use efficiency (RUE) and leaf parameters including leaf area index (LAI), areal leaf N content (N_AL) and leaf N concentration (N_L). Potatoes were grown in field at three N levels: no N (N1), 150 kg N ha⁻¹ (N2), 300 kg N ha⁻¹ (N3). N deficiency was quantified by NNI and RUE was generally calculated by estimating of the light absorbance on leaf area. NNI was used to evaluate the N effect on tuber yield, RUE, LAI, N_AL, and N_L. The results showed that NNI was negatively correlated with AE_N, N deficiencies (NNI<1) which occurred for N1 and N2 significantly reduced LAI, N_L and tuber yield; whereas the N deficiencies had a relative small effect on N_AL and RUE. To remove any effect other than N on these parameters, the actual ratio to maximum values were calculated for each developmental stage of potatoes. When the NNI ranged from 0.4 to 1, positive linear relationships were obtained between NNI and tuber yield, LAI, N_L, while a nonlinear regression fitted the response of RUE to NNI.     

Soil Organic Carbon,Black Carbon,and Enzyme Activity Under Long-Term Fertilization

The present study aims to understand the effects of long-term fertilization on soil organic carbon (SOC), black carbon (BC), enzyme activity, and the relationships among these parameters. Paddy field was continuously fertilized over 30 yr with nine different fertilizer treatments including N, P, K, NP, NK, NPK, 2NPK (two-fold NPK), NPK+manure (NPKM), and CK (no fertilization), N, 90 kg urea-N ha⁻¹ yr⁻¹; P, 45 kg triple superphosphate-P₂O₅ ha⁻¹ yr⁻¹; K, 75 kg potassium chloride-K₂O ha⁻¹ yr⁻¹; and pig manure, 22 500 kg ha⁻¹ yr⁻¹. Soil samples were collected and determined for SOC, BC content, and enzyme activity. The results showed that the SOC in the NPKM treatment was significantly higher than those in the K, P, and CK treatments. The lowest SOC content was found in the CK treatment. SOC content was similar in the N, NP, NK, NPK, 2NPK, and NPKM treatments. There was no significant difference in BC content among different treatments. The BC-to-SOC ratios (BC/SOC) ranged from 0.50 to 0.63, suggesting that BC might originate from the same source. Regarding enzyme activity, NPK treatment had higher urease activity than NPKM treatment. The urease activity of NPKM treatment was significantly higher than that of 2NPK, NP, N, P, K, CK, and NPKM treatment which produced higher activities of acid phosphatase, catalase, and invertase than all other treatments. Our results indicated that long-term fertilization did not significantly affect BC content. Concurrent application of manure and mineral fertilizers increased SOC content and significantly enhanced soil enzyme activities. Correlation analysis showed that catalase activity was significantly associated with invertase activity, but SOC, BC, and enzyme activity levels were not significantly correlated with one another. No significant correlations were observed between BC and soil enzymes. It is unknown whether soil enzymes play a role in the decomposition of BC.     

Abundance and Community Composition of Ammonia-Oxidizers in Paddy Soil at Different Nitrogen Fertilizer Rates

Ammonia oxidation, the first and rate-limiting step of nitrification, is carried out by both ammonia-oxidizing bacteria （AOB） and ammonia-oxidizing archaea （AOA）. However, the relative importance of AOB and AOA to nitrification in terrestrial ecosystems is not well understood. The aim of this study was to investigate the effect of the nitrogen input amount on abundance and community composition of AOB and AOA in red paddy soil. Soil samples of 10-20 cm （root layer soil） and 0-5 cm （surface soil） depths were taken from a red paddy. Rice in the paddy was fertilized with different rates of N as urea of N1 （75 kg N ha＂ yr-1）, N2 （150 kg N ha~ yrl）, N3 （225 kg N ha1 yrl） and CK （without fertilizers） in 2009, 2010 and 2011. Abundance and community composition of ammonia oxidizers was analyzed by real-time PCR and denaturing gradient gel electrophoresis （DGGE） based on amoA （the unit A of ammonia monooxygenase） gene. Archaeal amoA copies in N3 and N2 were significantly （P〈0.05） higher than those in CK and N1 in root layer soil or in surface soil under tillering and heading stages of rice, while the enhancement in bacterial amoA gene copies with increasing of N fertilizer rates only took on in root layer soil. N availability and soil NO3--N content increased but soil NH4＋-N content didn＇t change with increasing of N fertilizer rates. Otherwise, the copy numbers of archaeal amoA gene were higher （P〈0.05） than those of bacterial amoA gene in root lary soil or in surface soil. Redundancy discriminate analysis based on DGGE bands showed that there were no obvious differs in composition of AOA or AOB communities in the field among different N fertilizer rates. Results of this study suggested that the abundance of ammonia-oxidizers had active response to N fertilizer rates and the response of AOA was more obvious than that of AOB. Similarity in the community composition of AOA or AOB among different N fertilizer rates indicate that the community composition of ammonia-oxidizers was relatively stable in the paddy soil at least in short term for three years.     

施肥水平对不同氮效率水稻氮素利用特征及产量的影响

【目的】研究不同施肥水平下不同氮效率杂交水稻产量差异与氮素吸收和利用的关系,以期为水稻品种改良和高产高效栽培技术提供依据。【方法】以氮高效品种(德香4103)和氮低效品种(宜香3724)为材料,通过设置低肥(75 kg N·hm~(-2),37.5 kg P_2O_5·hm~(-2),75 kg K_2O·hm~(-2),记为N_1P_1K_1)、中肥(150 kg N·hm~(-2),75 kg P_2O_5·hm~(-2),150 kg K_2O·hm~(-2),记为N_2P_2K_2)、高肥(225 kg N·hm~(-2),112.5 kg P_2O_5·hm~(-2),225 kg K_2O·hm~(-2),记为N_3P_3K_3)3种施肥水平,并在各施肥水平下均增设一不施氮处理,研究其对不同氮效率水稻产量和氮素利用效率的影响及其结实期氮素吸收、转运和分配特性。【结果】品种与施肥水平对杂交稻主要生育时期及各生育阶段氮素的累积、转运、分配,以及氮素利用特征和产量均存在显著影响;品种对氮肥回收利用率、千粒重,以及总颖花数的影响均不同程度的高于施肥水平的调控效应;施肥水平对主要生育时期及各生育阶段氮素的累积,结实期叶片和茎鞘氮的运转,以及产量调控作用显著。N_2P_2K_2相对于N_1P_1K_1处理能促进不同氮效率水稻主要生育时期及各生育阶段氮素的累积,提高氮收获指数,促进结实期叶片和茎鞘中氮素的运转,进而显著提高稻谷产量及氮肥利用效率,且N_2P_2K_2均显著高于同品种下其他的肥料施用处理,为本试验最佳的氮磷钾肥施用模式;N_3P_3K_3处理易造成结实期叶片及茎鞘中氮滞留量增加,氮转运贡献率显著降低,导致产量及氮肥利用效率显著降低。氮高效品种具有总颖花数、结实率高的特征,其主要生育时期氮素累积量,氮素干物质生产效率,氮素稻谷生产效率及氮素收获指数等均显著高于氮低效品种,但千粒重并不是氮高效品种所独有的特征;此外,氮高效品种结实期更有利于叶片与茎鞘氮素的运转及穗部氮素的累积,尤其氮高效品种具有较高的茎鞘氮素转运率,其与氮肥生理利用率、回收利用率及农艺利用率均存在显著正相关性(r=0.699*—0.743*),是导致不同氮效率品种氮肥利用效率、产量差异的重要因子,可作为氮效率及品种鉴选的评价指标,也可以以进一步提高抽穗至成熟期氮高效水稻品种茎鞘氮素运转率,作为实现水稻高产与氮高效利用协调统一的另一重要途径。【结论】本试验条件下,氮高效品种具备的结实期茎鞘高氮素转运、高总颖花数及结实率是优于氮低效品种而形成产量差异的主要因素,N_2P_2K2_为氮高效品种配套的最优氮磷钾肥施用模式。提高抽穗期至成熟期氮累积量,促进叶片与茎鞘氮运转量,尤其应提高茎鞘氮素运转率,可实现高产与氮高效利用的同步提高。