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1.
With respect to the important effects of nitrogen (N) on plant growth and fruit production, a five-year experiment was performed to evaluate the effects of different sources of N fertilization including chemical and organic on the quantity and quality of citrus fruit. Using five-year old trees, different types of fertilization including ammonium sulfate, urea coated with sulfur, ammonium nitrate and manure were tested using seven treatments in five replicates from 2002 to 2007. Different plant quantitative and qualitative parameters were determined. The most effective strategy on fruit yield production was the use of urea coated with sulfur and manure with 92.46 kg ha?1 fruit yield followed by ammonium sulfate and manure (87.06 kg ha?1) and ammonium sulfate (86.43 kg ha?1). The combination of mineral and organic fertilization may be the most suitable fertilization strategy for citrus production.  相似文献   

2.
The effect of different levels and forms of nitrogen (N) fertilizer on cadmium (Cd) concentrations in potato (Solanum tuberosum L.) tubers, a large component of the northern European diet, was investigated with the aim of decreasing the Cd content. A high and a low Cd-accumulating cultivar were used in two field trials and a pot experiment. The N fertilizers tested were balanced N- phosphorus (P)- potassium (K) 11-5-18 + micronutrients, alkaline calcium nitrate and acidic ammonium sulfate at levels of 60, 160, and 240 kg N ha?1 at planting or (for the higher N doses) split between two or three occasions. The Cd concentration in tubers of both cultivars decreased when increasing the N fertilizer from 60 to 160 or 240 kg N ha?1, indicating that Cd uptake and translocation are not positively correlated to the growth rate of the potato plant. A strong positive linear correlation was found between the Cd concentration in leaves at 77 days after planting and the Cd concentration in tubers at harvest, irrespective of N treatment, although the Cd concentration was three-fold higher in the leaves. The genetic variation in leaf and tuber Cd accumulation was consistent, regardless of the form of N fertilizer used. Ammonium sulfate decreased soil pH and increased tuber Cd concentration in both cultivars compared with NPK fertilizer, possibly due to increased amounts of plant-available Cd arising from the pH decrease after ammonium sulfate application. The tuber Cd concentration in the low Cd-accumulating cultivar increased when fertilized with calcium nitrate, an effect attributed to Cd availability being influenced by the increased Ca2+ concentration.  相似文献   

3.
The objective was to evaluate the effect of nitrogen, associated to silicon, on soil chemical properties, nutritional status and yield of the second sugarcane ratoon. The experiment was carried out at a Haplustox, loamy texture. The treatments consisted of urea rates of 0, 40, 80, 120 and 160 kg ha?1 and two sources of correctives: silicate and lime. The use of nitrogen (N) associated with silicate and lime did not affect soil fertility; however, the use of silicate increased soil silicon content at harvest. Growth variables were not affected by the application of the treatments, except stalk number at harvest, which increased in the presence of silicon. N rates and the correctives did not affect the crop nutritional status, but affected the N and Si accumulation in the plant. The N rates increased the sugarcane ratoon yield regardless the use of silicate; however, they did not affect its technological quality.  相似文献   

4.
A field experiment was conducted to investigate the effect of nitrogen (N) application on the growth and metabolism of sugar beet (Beta vulgaris L.). Changes in nitrate, ammonium, soluble protein and pigment levels, nitrogen metabolism enzyme activity, biomass of leaves and beet, and sucrose and α-amino-N were studied in relation to five different NPK application rates (0, 50, 100, 150, and 200 kg N ha?1) and association with Azotobacter chrooccocum. The availability of nitrate and ammonium ions in the leaves proved to be influenced by the different nitrogen treatments. The most important enzymatic activities within nitrogen metabolism were affected negatively by the highest NPK rate. With increasing nitrogen supply, the concentration of α-amino-N increased considerably and that of sucrose decreased. Application of NPK had a significant positive effect on the growth and biomass production. The measured parameters of plants associated with A. chrooccocum were of similar magnitude comparing to the controls.  相似文献   

5.
Abstract

The objective of this paper was to evaluate the influence of different rates of biosolids on the soil nitrogen (N) availability for maize and its residuality. A field experiment was developed in a typic Argiudol located in the NE of the Buenos Aires Province. Maize was sown for two consecutive years 1997–1999. Biosolids from a sewage treatment plant of Buenos Aires outskirts were superficially applied to the soil and incorporated by plowing. There were eight treatments: Check; 8, 16, and 24 Mg of dry biosolid ha?1; 8 and 16 Mg of dry biosolid ha?1 applied one year before, 100 and 150 kg N ha?1 of calcium ammonium nitrate (CAN). The sampling and determinations were done during the second maize cycle. At presowing (PS), sowing (S), 6 expanded leaves (V6), 12 expanded leaves (V12), and Flowering (Fl) composite soil samples from 0–40 cm depth were obtained to determine ammonium and nitrate contents. At Fl maize plants were sampled in order to determine total biomass and N content. The N‐nitrate content in the soil was significantly increased by the biosolids application (p < 0.05), and varied for each increment depending on the biosolids rates and the phenological stage. After 30 days from the incorporation the increases of 1.19, 1.34, and 2.05% were observed for N‐nitrates for 8, 16, and 24 Mg ha?1, respectively. The contribution of mineral N from the biosolids was 2.48, 6.46, and 5.01 kg N Mg?1 when the rates were incremented from 0–8, 8–16, and 16–24 Mg ha?1, respectively. The nitrogen mineralization followed a release pattern with a maximum value of 296 kg N‐nitrate ha?1 at sowing for 24 Mg ha?1. Since then, the release of mineral nitrogen decreased significantly till Fl. The N‐nitrates values variation with the temperature adjusted to polinomic functions. The mineral N released from the biosolids increased as a response to the increment of soil temperature and then decreased due to the maize nitrogen absorption and the potentially mineralized nitrogen exhaustion. The application of 150 kg N ha?1 as CAN incremented significantly the soil N‐nitrate content and equalized 16 and 24 Mg of dry biosolids ha?1 at V6. But, no synchronism between the high nitrate releasing from biosolids and the increment in the nitrogen absorption by maize was observed. This fact generates a surplus of nitrate that incremented the potential of nitrogen loss by lixiviation. We observed a residual effect from the biosolids that were applied the previous year. This contribution represented the 35% of the maize requirements and was similar to the nitrate content observed in Bio 16. The biosolids might be a valuable source of nitrogen for maize crop if the synchronism between the soil supply and maize demand is observed in order to avoid nitrates surplus.  相似文献   

6.
The objective of this study was to determine the effect of nitrogen (N) application source and rate on silage corn (Zea mays L.). Urea, ammonium nitrate, and ammonium sulfate were compared at 50, 100, 150, and 200 kg N ha?1. The application of ammonium sulfate produced the highest plant height, leaf area index (LAI), total yield, and stem, leaf, and ear dry matter, followed by ammonium nitrate and urea. However, nitrogen sources had no marked effects on the content of protein, ash, oil, soluble carbohydrates, acid detergent fiber (ADF) and neutral detergent fiber (NDF). As the rate of nitrogen increased plant height, LAI, total yield, and stem, leaf, tassel, and ear dry matters, and protein, ash and oil contents increased while soluble carbohydrates, ADF, and NDF contents decreased. Ammonium sulfate was the most effective N source on production and 200 kg N ha?1 was the most effective N rate on corn yield and quality.  相似文献   

7.
ABSTRACT

Field experiments were carried out for three consecutive years (2003–2006) at Bangladesh Sugarcane Research Institute farm soil on plant (first crop after planting) and subsequent two ratoon crops of sugarcane. The main objectives of the study were to assess the direct and residual effects of organic and inorganic fertilizer on growth, yield, and juice quality of plant and ratoon crops. The plant crop consisted of four treatments. After harvesting of plant crop to evaluate the residual effects on ratoon crop the plots were subdivided except the control plot. Thus, there were seven treatments in the ratoon crop. Application of recommended fertilizer [nitrogen (N150), phosphorus (P52), potassium (K90), sulfur (S35), and zinc (Zn3) kg ha? 1] singly or 25% less of it either with press mud or farmyard manure (FYM) at 15 t ha? 1 produced statistically identical yield ranged from 67.5 to 69.0 t ha? 1 in plant crop. In the ratoon experiment when the recommended fertilizer was applied alone or 25% less of its either with press mud or FYM at 15 or even 7.5 t ha? 1 again produced better yield; it ranged from 64.8 to 69.2 in first ratoon and 68.2 to 76.5 t ha? 1 in second ratoon crops. Results showed that N, P, K, and S content in leaf progressively decreased in ratoon crops over plant crop. Juice quality parameters viz. brix, pol, and purity % remained unchanged both in plant and ratoon crops. Furthermore, organic carbon (C), available N, P, K, and S were higher in post harvest soils that received inorganic fertilizer in combination with organic manure than control and inorganic fertilizer treated soil. It may be concluded that the application of 25% less of recommended fertilizer (N112, P40, K68, S26, and Zn2.2.5 kg ha? 1) either with press mud or FYM at 15 t ha? 1 was adequate for optimum yield of plant crop. Results also suggest that additional N (50% extra dosage) keeping all other fertilizers at the same level like plant crop i.e. N168, P40, K68, S26, and Zn2.25 kg ha? 1 either with press mud or FYM at 7.5 t ha? 1 may be recommended for subsequent ratoon crops to obtain good yield without deterioration in soil fertility.  相似文献   

8.
The optimum dose of nitrogen (N) and phosphorus (P) for Withania somnifera was determined by utilizing graded levels of 0, 30, 45 and 60 kg ha?1 N and 0, 13, 26 and 40 kg ha?1 P in two separate simple randomized pot experiments. Soil-application of 45 kg N ha?1 and 26 kg P ha?1 proved the best dose for increasing shoot and root length, leaf area, fresh and dry weight of shoot and root, total chlorophyll and leaf-N, P, and potassium (K) content, nitrate reductase, and carbonic anhydrase activity, total alkaloid content, seed-yield per plant, root- yield per plant and berries per plant. While 30 kg N ha?1 proved best for root length, fresh and dry weights, as well as root-yield per plant. However, the effect of N and P fertilizers on carotenoid content, seeds per berry and 100-seed weight were insipid. Leaf- P remained unaffected by nitrogen application.  相似文献   

9.
Determining a critical nitrogen dilution curve for sugarcane   总被引：1，自引：0，他引：1  
Adequate measurements of the nitrogen (N) concentration in the aboveground biomass of sugarcane throughout the growth cycle can be obtained using the critical N dilution curve (CNDC) concept, which provides an N‐nutrition index (NNI). The aim of this work was to determine the CNDC value for Brazilian sugarcane variety SP81‐3250, establish the critical concentration of N, and determine the NNI in the aboveground biomass throughout the cane plant and first ratoon crop cycles. The study was performed in three experimental areas located in São Paulo, Brazil, during the crop cycles of 2005/2006 (18‐month cane plant) and 2006/2007 (first ratoon). The plant cane crop was fertilized with treatments of 40, 80, or 120 kg N ha–1 and a control treatment without N. After the plant cane harvest, rates of 0, 50, 100, or 150 kg N ha–1 were applied to the control plot and the 120 kg N ha–1–treatment plot in a split‐plot experimental design with four repetitions. Throughout both sugarcane cycles, measurements of aboveground biomass were used to determine the dry‐mass (DM) production and N concentration for each treatment. CNDC varied between the growth cycles, with a higher N concentration observed in the initial stages of the first ratoon and a lower N dilution observed throughout the plant cane cycle. The NNI value indicated excessive N storage in the initial stages and limiting concentrations at the end of the growth cycle. CNDC and NNI allow for the identification of the N‐nutrition variation rate and the period in which the nutrient concentration limits the production of aboveground biomass. The equations for the critical N (Ncr) level obtained in this study for plant cane (Ncr = 19.0 DM–0.369) and ratoons (Ncr = 20.3 DM–0.469) can potentially be used as N‐nutritional diagnostic parameters for sugarcane N nutrition.  相似文献   

10.
The current study aimed to verify the effect of the inoculant constituted by diazotrophic bacteria applied in different ways, associated to different nitrogen (N)-fertilizer doses, on the yield and N utilization efficiency of sugarcane ratoon. The use of inoculant did not affect the N content in leaves, the chlorophyll content, tiller number, stalk diameter, or any of the other assessed technological attributes. However, the use of inoculant associated to doses of 60 and 90 kg N ha?1 promoted increase in stalk yield, dry matter, and N accumulation and efficiency of N fertilizer, and, on the other hand, the association of inoculant with 120 kg N ha?1 caused reduction of these parameters.  相似文献   

11.
The objective of this growth chamber study was to evaluate the effect of adding N-(n-butyl) thiophosphoric triamide (NBPT) and dicyandiaminde (DCD) to urea fertilizer, on the physiology and growth of cotton (Gossypiumhirsutum L.) under normal and high temperatures. Treatments consisted of two day temperature regimes, 30°C and 38°C, and five nitrogen fertilization applications: unfertilized control, 125 kg ha?1 of urea, 93 kg ha?1 of urea, 93 kg ha?1 urea + NBPT, and 93 kg ha?1 urea + NBPT + DCD. The addition of NBPT to urea fertilizer had positive effects on leaf chlorophyll, leaf area, dry matter, nitrogen (N) uptake, and N use efficiency. The absence of a significant interaction effect indicated that N fertilization was not influenced by temperature. Deficiency of N significantly decreased leaf chlorophyll, increased glutathione reductase, decreased protein and increased leaf nitrate reductase. Physiological changes under high temperature included increased plant N uptake, glutamine synthetase, leaf chlorophyll, protein content, plant height and leaf area were due to high N uptake and utilization.  相似文献   

12.
With regard to the low cation-exchange capacity and large saturated hydraulic conductivity of sandy soils, a field experiment was carried out in 2006–2007 to determine the impact of zeolite on nitrogen leaching and canola production. Four nitrogen (N) rates (0, 90, 180, and 270 kg ha–1) and three zeolite amounts (3, 6 and 9 t ha?1) were included as treatments. The results demonstrated that the highest growth parameters and seed yield were attained with 270 kg N ha?1 and 9 t zeolite ha?1. However, the highest and the lowest seed protein percentage and oil content were obtained with 270 kg N ha?1 accompanied by 9 t zeolite ha?1, respectively. Nitrate concentration in drained water was affected by nitrogen and zeolite. The lowest and highest leached nitrate values were found in control without N and zeolite (N0Z0) and in treatments with the highest N supply without zeolite (N270Z0), respectively. In general, nitrogen-use efficiency decreased with an increase in N supply. Application of 9 t zeolite ha?1 showed higher nitrogen use efficiency than other zeolite amounts. Also, application of more N fertilizer in soil reduced nitrogen uptake efficiency. In total, application of 270 kg N ha?1 and 9 t zeolite ha?1 could be suggested as superior treatment.  相似文献   

13.
A field experiment was conducted at ICAR-Indian Institute of Sugarcane Research, Lucknow, with three tillage practices (T1: Control- two times ploughing with harrow and cultivator, each followed by planking before sugarcane planting; T2: Deep tillage with disc plough (depth 25–30 cm) before planting followed by harrowing, cultivator, and planking; and T3: Subsoiling at 45–50 cm and deep tillage with disc plough/moldboard plough (depth 25–30 cm) followed by harrowing, cultivator, and planking before planting, two soil moisture regimes (M1: 0.5 irrigation water (IW)/cumulative pan evaporation (?CPE) ratio and M2: 0.75 IW/CPE ratio) at 7.5 cm depth of IW, and four N levels (N1- 0, N2- 75, N3- 150, and N4-225 kg N ha?1) in sugarcane plant crop. Deep tillage and subsoiling increased porosity and reduced bulk density in surface/subsurface soil. Further, these physical changes also improved soil biological and chemical properties responsible for higher crop growth and yield. Deep tillage and subsoiling reduced the compaction by 6.12% in 0–15 cm depth in sugarcane plant crop at maximum tillering stage. The highest N uptake (158.5 kg ha?1) was analyzed with deep tillage and subsoiling compared to all other tillage practices. Maintaining suboptimal moisture regime with deep tillage and subsoiling showed the highest IW use efficiency (157.16 kg cane kg?1 N applied). Mean soil microbial biomass carbon (SMBC) in ratoon crop was higher compared to plant crop. During initial tillering stage, ratoon crop showed higher SMBC with application of deep tillage and subsoiling (1209 mg CO2-C g?1 soil day?1) at 0–15 cm depth and 1082.9 mg CO2-C g?1 soil day?1 at 15–30 cm depth. Thus, it could be concluded that besides improving sugarcane yield, soil health could be sustained by adopting subsoiling (45–50 cm depth) and deep tillage (20–25 cm depth), with soil moisture regime of 0.75 IW/CPE and application of 150 kg N ha?1 in sugarcane (plant crop).  相似文献   

14.
Fate of fertilizer nitrogen.   总被引：3，自引：0，他引：3  
Results are presented from a three year lysimeter investigation, employing single (15NH4NO3) and double (15NH415NO3) labelled ammonium nitrate to study the uptake of soil and fertilizer nitrogen by cut ryegrass at 250, 500 and 900 kg N ha?1 a?1. Average annual recoveries of nitrogen were equivalent to 99,76 and 50% of the nitrogen added at 250, 500 and 900 kg N ha?1, respectively. At 250 kg N ha?1 the difference between the overall nitrogen recovery and the fertilizer recovery was almost entirely attributable to pool substitution resulting from mineralization/immobilization turnover (MIT). At 900 kg N ha?1 both the low overall recovery of nitrogen and the low fertilizer recovery reflected the large excess of available nitrogen over crop requirements. No evidence of ‘priming’ was obtained. Analysis of the results from single and double labelled lysimeters using simultaneous equations indicated that at 250 kg N ha?1,～70% of the nitrogen in the crop was derived from the ammonium pool. At 500 kg N ha?1 this dropped to 64%, while at 900 kg N ha?1 the figure was 59%. There was a suggestion that at the lower application rates, preferential uptake of ammonium was occurring but that as N supply exceeded crop requirements, nitrate was the major N source. Despite the preferential exploitation of the ammonium pool, at 250 and 500 kg N ha?1 pool substitution resulting from MIT resulted in lower recoveries of fertilizer ammonium compared with fertilizer nitrate.  相似文献   

15.
Foliar nutrient analysis is a useful diagnostic tool to complement soil testing as a best‐management practice with sugarcane (Saccharum spp.). This study was conducted to determine sugarcane production limits at leaf nutrient concentrations less than optimum. Eight Florida sugarcane growers participated in a survey of leaf nutrient values in 2004, 2005, and 2006. A total of 412 leaf samples were collected from individual commercial sugarcane fields, from which there were 389 harvest data/leaf data combinations. Fields were selected to be representative of plant cane, first ratoon, and second ratoon crops; mineral and organic soils of the area; and major commercial sugarcane cultivars. Leaf silicon (Si), magnesium (Mg), and manganese (Mn) concentrations had the strongest correlations with tons sugarcane ha?1 on organic soils, and leaf nitrogen (N), Mg, and Si concentrations had the strongest correlations with tons sugarcane ha?1 on mineral soils. Boundary lines were used to define practical limits of tons sugarcane ha?1 for leaf nutrient concentrations less than optimum. A table was developed that provides approximate leaf concentrations of nine nutrients at which 10 and 25% losses in relative tons sugarcane ha?1 were estimated. Boundary‐line analysis indicated that sugarcane production was most limited nutritionally in survey fields by insufficient Mg, iron, N, and Si on mineral soils and by insufficient Si and Mn on organic soils.  相似文献   

16.
《Journal of plant nutrition》2013,36(8):1561-1580
Abstract

The Magruder plots are the oldest continuous soil fertility wheat research plots in the Great Plains region, and are one of the oldest continuous soil fertility wheat plots in the world. They were initiated in 1892 by Alexander C. Magruder who was interested in the productivity of native prairie soils when sown continuously to winter wheat. This study reports on a simple estimate of nitrogen (N) balance in the Magruder plots, accounting for N applied, N removed in the grain, plant N loss, denitrification, non‐symbiotic N fixation, nitrate (NO3 ?) leaching, N applied in the rainfall, estimated total soil N (0–30 cm) at the beginning of the experiment and that measured in 2001. In the Manure plots, total soil N decreased from 6890 kg N ha?1 in the surface 0–30 cm in 1892, to 3198 kg N ha?1 in 2002. In the Check plots (no nutrients applied for 109 years) only 2411 kg N ha?1 or 35% of the original total soil organic N remains. Nitrogen removed in the grain averaged 38.4 kg N ha?1 yr?1 and N additions (manure, N in rainfall, N via symbiotic N fixation) averaged 44.5 kg N ha?1 yr?1 in the Manure plots. Following 109 years, unaccounted N ranged from 229 to 1395 kg N ha?1. On a by year basis, this would translate into 2–13 kg N ha?1 yr?1 that were unaccounted for, increasing with increased N application. For the Manure plots, the estimate of nitrogen use efficiency (NUE) (N removed in the grain, minus N removed in the grain of the Check plots, divided by the rate of N applied) was 32.8%, similar to the 33% NUE for world cereal production reported in 1999.  相似文献   

17.
Nitrogen (N) deposition is a major threat to the semiarid Mediterranean ecosystems. We simulated a gradient of N deposition (0, 10, 20 and 50 kg N ha?1 year?1?+?6.4 kg N ha?1 year?1 ambient deposition) in a Mediterranean shrubland from central Spain. In autumn 2011 (after 4 years of experimental duration), soil cores were taken to extract the soil fauna. Acari (45.54%) and Collembola (44.00%) were the most represented taxonomical groups, and their abundance was negatively related to soil pH. Simulated N deposition had an impact on the total number of individuals in soil as well as on Collembola and Pauropoda abundance. Collembola abundance increased with N loads up to 20 kg N ha-1 year-1 and then decreased. This response was attributed to soil acidification (between 0 and 20 kg N ha-1 year-1) and increased soil ammonium (between 20 and 50 kg N ha-1 year-1). Pauropoda were favoured by additions of 50 kg N ha-1 year-1, and it was the only taxonomical group whose abundance was exclusively related to N deposition, suggesting their potential as bioindicators. Contrary to predictions, there was a negative relationship between soil faunal abundance and plant diversity. In conclusion, soil faunal communities from semiarid Mediterranean ecosystems in central Spain seem to be primarily influenced by soil chemistry (mainly pH) but are also susceptible to increased N deposition. The main drivers of change under increased N deposition scenarios seem to be soil acidification and increased ammonium in soils where nitrate is the dominant mineral N form.  相似文献   

18.
Abstract

The single‐year response of soil inorganic nitrogen (N) content and indices of red raspberry (Rubus ideaus L.) yield, vigor, and N status to rate and source of fertilizer N were determined. Twenty‐nine trials were conducted in commercial plantings from 1994 to 1996. Treatments were 0, 55, or 110 kg N ha?1 as ammonium nitrate or 55 kg N ha?1 as a slow‐release fertilizer product containing 60% polycoated sulfur‐coated urea and 40% urea. Soil nitrate (NO3) content frequently increased during the growing season, indicating that soil N supply was nonlimiting. The plant indices were generally insensitive to fertilizer‐N rate under these high‐N fertility conditions. Soil nitrate content measured after berry harvest was frequently excessive even at the recommended N rate and can be used to identify fields with excess N fertility. The slow‐release N fertilizer provided limited benefits compared with use of ammonium nitrate.  相似文献   

19.
Controlled-release urea (CRU) and its placement method in rice production were investigated during 2007 and 2008 seasons. Controlled-release urea was applied at 62.5, 125, and 187.5 kg nitrogen (N) ha?1, and the urea was 187.5 kg N ha?1. All the CRU treatments were applied to the nursery beds once, and they were brought into the paddy field during transplanting, while the urea treatment was split into three applications from the plowing to the harvest. The results showed that rice seedlings with CRUs germinated and grow well and there was no salt damage at the nursery stage. The CRU treatment with 125 kg N ha?1 had 33% less N than urea treatment (187.50 kg N ha?1), but it produced significantly higher grain and straw yields, higher total N uptake and total apparent N uptake efficiency. In addition, all the CRU treatments effectively decreased floodwater ammonium (NH4 +)-N and nitrate (NO3 ?)-N concentrations, pH, and N runoff.  相似文献   

20.
It was hypothesized that the application of eucalyptus biochar enhances nutrient use efficiencies of simultaneously supplied fertilizer, as well as provides additional nutrients (i.e., Ca, P, and K), to support crop performance and residual effects on subsequent crops in a degraded sandy soil. To test this hypothesis, we conducted an on‐farm field experiment in the Khon Kaen province of Northeastern Thailand to assess the effects of different application rates of eucalyptus biochar in combination with mineral fertilizers to upland rice and a succeeding crop of sugarcane on a sandy soil. The field experiment consisted of three treatments: (1) no biochar; (2) 3.1 Mg ha?1 biochar (10.4 kg N ha?1, 3.1 kg P ha?1, 11.0 kg K ha?1, and 17.7 kg Ca ha?1); (3) 6.2 Mg ha?1 biochar (20.8 kg N ha?1, 6.2 kg P ha?1, 22.0 kg K ha?1, and 35.4 kg Ca ha?1). All treatments received the same recommended fertilizer rate (32 kg N ha?1, 14 kg P ha?1, and 16 kg K ha?1 for upland rice; 119 kg N ha?1, 21 kg P ha?1, and 39 kg K ha?1 for sugarcane). At crop harvests, yield and nutrient contents and nitrogen (N) use efficiency were determined, and soil chemical properties and pH0 monitored. The eucalyptus biochar material increased soil Ca availability (117 ± 28 and 116 ± 7 mg kg?1 with 3.1 and 6.2 Mg ha?1 biochar application, respectively) compared to 71 ± 13 mg kg?1 without biochar application, thus promoting Ca uptake and total plant biomass in upland rice. Moreover, the higher rate of eucalyptus biochar improved CEC, organic matter, available P, and exchangeable K at succeeding sugarcane harvest. Additionally, 6.2 Mg ha?1 biochar significantly increased sugarcane yield (41%) and N uptake (70%), thus enhancing N use efficiency (118%) by higher P (96%) and K (128%) uptake, although the sugar content was not increased. Hence, the application rate of 6.2 Mg ha?1 eucalyptus biochar could become a potential practice to enhance not only the nutrient status of crops and soils, but also crop productivity within an upland rice–sugarcane rotation system established on tropical low fertility sandy soils.  相似文献   

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