Sequential extraction methods for soil organic nitrogen

(pp. 825–831)
This study was carried out to clarify the effects of soil nitrate before cultivation and amounts of basal-dressed nitrogen on additional N application rate and yields of semi-forced tomato for three years from 1998 to 2000. The amounts and timing of additional N dressing were determined based on diagnosis of petiole sap nitrate. The top-dressing was carried out with a liquid fertilizer when the nitrate concentration of a leaflet's petiole sap of leaf beneath fruit which is 2–4 cm declined below 2000 mg L⁻¹.
For standard yield by the method of fertilizer application based on this condition, no basal-dressed nitrogen was required when soil nitrate before cultivation was 150 mg kg⁻¹ dry soil or higher in the 0–30 cm layer; 38 kg ha⁻¹ of basal-dressed nitrogen, which corresponds to 25% of the standard rate of fertilizer application of Chiba Prefecture, was optimum when soil nitrate before cultivation was 100150 mg kg⁻¹ dry soil; 75 kg ha⁻¹ of basal-dressed nitrogen, which corresponds to 50% of the standard, was optimum when soil nitrate before cultivation was under 100 mg kg⁻¹ dry soil. A standard yield was secured and the rate of nitrogen fertilizer application decreased by 49–76% of the standard by keeping the nitrate concentration of tomato petiole sap between 1000–2000 mg L⁻¹ from early harvest time to topping time under these conditions.     

Ideal transition pattern of nitrate concentration for improving quality of spinach Spinacea oleracea L. and effect of drip fertigation on the sugar and oxalate concentration

(pp. 25–32)

The effectiveness of drip fertigation, which is known to control fertilizer application, for reducing nitrate in spinach and for improving the other qualities of spinach was investigated. Fertilizer application can be controlled effectively by drip fertigation. In 2002 and 2003, two spinach cultivars were grown in a plastic greenhouse with 4, 8 or 12 g N m^?2 of fertilizer application by drip fertigation, and with 8, 12 or 16 g N m^?2 of fertilizer application as a basal application. Nitrate concentration of petiole sap extracted by a garlic squeezer was significantly correlated with the water-extractable nitrate concentration. Nitrate concentrations of petiole sap extracted from plants treated with 12, 8 and 4 g N m^?2 of fertilizer by drip fertigation were constant, gradually decreased and significantly decreased, respectively, during the last 2 weeks. When nitrate concentration decreased during the last week, nitrate concentration in spinach at harvest was less than 3,000 mg kg^?1 FW. Thus it was thought that the pattern of the time course of nitrate in petiole xylem sap is a good indicator for getting spinach with low nitrate. The sugar concentration was negatively correlated with applied nitrogen quantity and the nitrate concentration. The total oxalic acid concentration in spinach treated by drip fertigation was significantly lower than that in spinach treated by basal application, independent of the amount of applied nitrogen. Thus drip fertigation is advantageous for improving crop quality.     

A lysimeter study of the fate of fertilizer nitrogen in spring barley crops grown on shallow soil overlying Chalk: crop uptake and leaching losses

The objective of this work was to determine the fate of fertilizer nitrogen (labelled with nitrogen-15) applied to an undisturbed shallow soil overlying Chalk contained in 10 lysimeters (80 cm diameter, 135 cm deep). Measurements are reported of the nitrogen uptake by four spring barley crops and the rate and extent of leaching of nitrate beyond the roots. The crops were fertilized with 0, 80 or 120 kg N ha^?1 in each of four years, but only the first application in 1977 was labelled with nitrogen ?15. Rainfall and irrigation approximated to the long-term average, but in two treatments dry or wet spring conditions were imposed for the 10 weeks after sowing the first crop in 1977. The dry matter and grain yields of the spring barley crops varied from year to year in the ranges 8.7–14.0 t ha^?1 and 3.5–6.1 t ha^?1 respectively. The total nitrogen harvested in the crop approximated to the amount of nitrogen applied in each year with an apparent recovery of fertilizer in the range 38–76%. The recovery of nitrogen derived from fertilizer (labelled with nitrogen-15) was 46–54% in the first crop and after 2 years rapidly declined to below 1%. The total amount of nitrogen-15 labelled fertilizer recovered in four barley crops was 49–57% of that applied. Mean annual nitrate concentrations in water draining from the base of the lysimeters were in the range 11.8–26.7 mg N 1^?1 and did not differ significantly between nitrogen fertilizer treatments (0, 80 and 120 kg N ha^?1 a^?1). In all treatments nitrate concentrations varied considerably within each growing season, with a cycle of peaks and troughs. Annual losses of nitrate were in the range 39–128 kg N ha^?1, and the mean annual losses over the 4 years varied between lysimeters from 65 to 83 kg N ha^?1. Nitrogen-15 labelled nitrate was detected in the first drainage water collected in autumn following its spring application, 5 months earlier. Recovery of fertilizer-derived nitrogen in drainage water was greatest during the winter following the second barley crop, and was 3.4–3.7% of the nitrogen-15 applied. Over the 4 years of the experiment 6.3–6.6% of labelled fertilizer was accounted for in drainage water, representing 2–3% of the total nitrogen lost by leaching.     

The influence of phosphate fertilizer application levels and cultivars on cadmium uptake by Komatsuna (Brassica rapa L. var. perviridis)

Cadmium (Cd) is a common impurity in phosphate fertilizers and application of phosphate fertilizer may contribute to soil Cd accumulation. Changes in Cd burdens to agricultural soils and the potential for plant Cd accumulation resulting from fertilizer input were investigated in this study. A field experiment was conducted on Haplaquept to investigate the influence of calcium superphosphate on extractable and total soil Cd and on growth and Cd uptake of different Komatsuna (Brassica rapa L. var. perviridis) cultivars. Four cultivars of Komatsuna were grown on the soil and harvested after 60 days. The superphosphate application increased total soil Cd from 2.51 to 2.75?mg?kg^?1, 0.1?mol?L^?1 hydrochloric acid (HCl) extractable Cd from 1.48 to 1.55?mg?kg^?1, 0.01?mol?L^?1 HCl extractable Cd from 0.043 to 0.046?mg?kg^?1 and water extractable Cd from 0.0057 to 0.0077?mg?kg^?1. Cd input reached 5.68?g?ha^–1 at a rate of 240?kg?ha^–1 superphosphate fertilizer application. Superphosphate affected dry-matter yield of leaves to different degrees in each cultivar. ‘Nakamachi’ produced the highest yield in 2008 and ‘Hamami No. 2’ in 2009. Compared with the control (no phosphate fertilizer), application of superphosphate at a rate of 240?kg?ha^–1 increased the Cd concentration in dry leaves by 0.14?mg?kg^?1 in ‘Maruha’, 1.03?mg?kg^?1 in ‘Nakamachi’, 0.63?mg?kg^?1 in ‘SC8-007’ in 2008, and by 0.19?mg?kg^?1 in Maruha’, 0.17?mg?kg^?1 in ‘Hamami No. 2’, while it decreased by 0.27?mg?kg^?1 in ‘Nakamachi’ in 2009. Field experiments in two years demonstrated that applications of different levels of calcium superphosphate did not influence Cd concentration in soil and Komatsuna significantly. However, there was a significant difference in Cd concentration of fresh and dry Komatsuna leaves among four cultivars in 2008 and 2009. The highest Cd concentration was found in the ‘Nakamachi’ cultivar (2.14?mg?kg^?1 in 2008 and 1.91?mg?kg^?1 in 2009). The lowest Cd concentration was observed in the ‘Maruha’ cultivar (1.51?mg?kg^?1?dry weight (DW)) in 2008 and in the ‘Hamami No. 2’ cultivar (1.56?mg?kg^?1?DW) in 2009. A decreasing trend in Cd concentration was found in ‘Nakamachi’, followed by ‘SC8-007’, ‘Hamami No. 2’ and ‘Maruha’ successively. It is necessary to consider a low-uptake cultivar for growing in a Cd polluted soil. In these two years’ results, ‘Maruha’ cultivar was the lowest Cd uptake cultivar compared to the others.     

Nitrogen application effects on forage sorghum production and nitrate concentration

Abstract

Forage sorghum (Sorghum bicolor (L.) Moench) is an important annual forage crop but prone to high nitrate concentration which can cause toxicity when fed to cattle (Bos taurus and Bos indicus). Two field experiments were conducted over six site-years across Kansas to determine the optimum nitrogen (N) rate for no-till forage sorghum dry matter (DM) yield and investigate the effect of N fertilization on sorghum forage nitrate content. A quadratic model described the relationship between sorghum DM and N rate across the combined site-years. Maximum DM yield of 6530?kg ha^?1 was produced with N application rate of 100?kg N ha^?1. The economic optimum N rate ranged from 55 to 70?kg N ha^?1 depending on sorghum hay price and N fertilizer costs. Crude protein concentration increased with N fertilizer application but N rates beyond 70?kg N ha^?1 resulted in forage nitrate concentrations greater than safe limit of 3000?mg kg^?1. Nitrogen uptake increased with N fertilizer application but nitrogen use efficiency and N recovery decreased with increasing N fertilizer rates. In conclusion, forage sorghum required 55–70?kg N ha^?1 to produce an economic optimum DM yields with safe nitrate concentration.     

Potential mineralization and nitrification in volcanic grassland soils in Chile

Abstract

A proportion of the nitrogen (N) applied to grasslands as organic or inorganic fertilizers can be lost to water courses as nitrate and to the atmosphere as nitrous and nitric oxides. Volcanic soils from Chile are not generally prone to leaching, possibly due to net immobilization of nitrate and/or ammonium, and/or due to inhibition of nitrification by either chemical or physical processes. In laboratory studies we found large mineralization potentials in soils from three different Chilean soils after 17 weeks of incubation, totalling 215 and 254 mg kg^?1 dry soil for two Andisols and 127 mg kg^?1 dry soil in an Ultisol. Nitrification occurred after a short period, and was lowest in the Ultisol. In addition, microbial analysis showed nitrifiers to be present in all three soils. Adsorption of ammonium was two-fold stronger than for nitrate, ranging from 29 to 180 kg N ha^?1. The highest potential for N adsorption in the 0–60 cm soil profile was with the Ultisol (398 kg N ha^?1), but was similar in both Andisols (193 and 172 kg N ha^?1, respectively). The combination of ammonium retention together with delayed nitrification could account for the low leaching rates in these soils.     

Potassium fertilization on sandy soils in relation to soil test,crop yield and K-leaching

To study the influence of potassium (K) fertilizer rate on soil test K values, crop yield, and K-leaching in sandy soils, four long-term fertilizer experiments (0–60–120–180 kg K ha^?1 a^?1) were initiated in 1988 in northern Germany on farmers fields. Clay content of the plow layer was about 4%, and organic matter between 2% and 5%. Plant available soil K was estimated with the double lactate (DL) method. Small grain cereals (rye and barley) did not respond to K fertilization in the 7-year period even though the soil test value of the K-0 plots decreased from ca. 90 to ca. 30 mg K_DL kg^?1 within 3 years. This value remained almost constant thereafter. Crop removal (including straw) of 75 kg K ha^?1 a^?1 was therefore apparently supplied from nonexchangeable K fractions. Compared to the optimum, no K application reduced the yield of potato by up to 21%, and that of white sugar yield up to 10%. Maximum potato yield was obtained by annually applying 60 kg K ha^?1 which resulted in a test value of 60 mg K_DL kg^?1 soil. Maximum potato yield was also obtained at 40 mg K_DL kg^?1 soil, however, with a single application of 200 kg K ha^?1. Similar results were obtained with sugar beet. This indicates that for maximum yield, even for K demanding crops, it is not necessary to maintain K_DL values above 40 mg K kg^?1 soil throughout the entire crop rotation. Soil test values increased roughly proportional to the K fertilizer level. About 120 kg fertilizer K ha^?1 a^?1, markedly more than crop K removal, was required to maintain the initial K_DL of 90 mg kg^?1. The K concentration of the soil solution in the top soil measured after harvest was increased exponentially by K fertilizer level and so was K leaching from the plow layer into the rooted subsoil. The leached quantity increased from 22 kg K ha_?1 a_?1 in the plot without K application to 42.79 and 133 kg Kha^?1 a^?1 in plots supplied with 60, 120 and 180 kg K ha^?1 a^?1 respectively. Soil test values around 100 mg K_DL kg^?1 on sandy soils, as often found in the plow layer of farmers fields, lead to K leaching below the root zone that may exceed the critical K concentration of 12 mg K T^?1 for drinking water.     

Effect of enriched municipal solid waste compost application on soil available macronutrients in the rice field

Abstract

A study was conducted in the Department of Environmental Sciences, Tamil Nadu Agricultural University, Coimbatore, India, to transform the normal compost into bioactive compost, which has multiple benefits to the crop system. The key players in this transformation process were Azotobacter sp., Pseudomonas sp., Phosphobacteria sp. and the waste materials like poultry litter and spent wash. This enrichment process increases both the quality and nutrient content of the municipal solid waste compost significantly. A study was carried out to evaluate the effect of application of different levels of enriched municipal solid waste compost on the availability of the macronutrient content to the rice field soil. The effect of enriched compost on soil available nutrients was significant. The soil ammonium nitrogen and soil nitrate nitrogen content was found to be high in the plots where the enriched compost was applied along with inorganic fertilizer with the values of 38.87 mg kg^?1 and 32.87 mg kg^?1, respectively. In addition, the availability decreased towards crop growth. The soil available P and K were also increased with enriched compost application to about 22.46 kg ha^?1 and 647 kg ha^?1 compared with control values of 19.44 kg ha^?1 and 518 kg ha^?1, respectively. Both phosphorus and potassium content decreased towards advancement of crop growth.     

Petiole N,P, K Concentrations and Yield of the Potato Cultivar Molli from Certified Organic Amendments and Fertilizer Formulations

This study evaluated the petiole uptake of nitrogen, phosphorus, potassium, and sulfur (N, P, K, and S) by the potato from two seed meals, mint compost, and five commercially available organic fertilizers under an irrigated certified organic production system. Available soil nitrate (NO₃-N) and ammonium (NH₄-N) from each amendment averaged 115 kg N ha^?1 at application and 25 kg N ha^?1 30 d after planting through harvest, with minor differences between fertilizers. Petiole N declined from an average of 25,000 mg N kg^?1, 4 wk after emergence to 3,000 mg N kg^?1 prior to harvest. Petiole P and K concentrations were maintained above 4,000 mg P kg^?1, 10,000 mg K kg^?1, and 2,000 mg S kg^?1 tissue, respectively, throughout the growing season in all treatments. Tuber yields were not different between fertilized treatments averaging 53 Mg ha^?1. This study provides organic potato growers baseline information on the performance of a diverse array of organic fertilizers and amendments.     

Nitrogen and Potassium Fertilization Responses of Potato (Solanum tuberosum) cv. Spunta

A potato field experiment was conducted for 2 consecutive years to determine the effects of nitrogen (N) and potassium (K) fertilization rates on the yield and quality of potato cv. Spunta cultivated on soil low in N and K. A 3?×?4 complete factorial experiment was used with three rates of nitrogen (330, 495, and 660 kg N ha^–1) and four rates of potassium (112, 225, 450, and 675 kg K₂Ο ha^–1). An additional treatment without fertilization was used as the control. On soils low in N and K, potatoes showed low yield response to K fertilizer. The greatest tuber yields for both years were achieved at 495 kg N ha^–1 and 112 kg K₂O ha^–1 (29.81 t ha^–1) and 225 kg ha^–1 (27.13 t ha^–1), respectively. Differences in mean fresh weight due to treatment application were not significant. Application of 495 kg N ha^–1 significantly reduced harvest index (the ratio of tuber dry weight to the total dry weight at harvest) compared to 330 kg N ha^–1, but at 660 kg N ha^–1 harvest index achieved the greatest significant value. Potassium fertilization had no significant influence on harvest index. Nitrogen rates positively influenced the number of tubers. The addition of 450 kg K₂O ha^–1 significantly enhanced the number of tubers compared to the lower K rates, and the number was significantly decreased by the application of 675 kg K₂O ha^–1. Tuber dry-matter concentration was significantly promoted by N fertilization in both cultivation years, but it was negatively affected by K fertilization in the first year of cultivation. There was no change in tuber N with N application, but N application strongly increased nitrate (NO₃) concentration, which fluctuated between 360 and 1382 mg kg^–1 wet mass. Tuber NO₃ was negatively correlated with tuber yield, indicating that high levels of NO₃ in tubers can adversely affect yield. Tuber response to K fertilization was not in accordance with the rate of applied nutrient.     

Effect of nitrogen forms on reduction of manganese oxides in an Oxisol by plant root exudates

Reductive dissolution of soil manganese (Mn) oxides increases potential toxicity of Mn²⁺ to plants. In order to examine the effect of nitrogen forms on reduction of Mn oxides in rhizosphere soil, a rhizobox experiment was employed to investigate the reduction of Mn oxides due to the growth of soybean and maize in an Oxisol with various contents of NO₃^–-N and NH₄⁺-N and a total N of 200 mg kg^?1. The results showed that exchangeable Mn²⁺ in rhizosphere soil was 9.6–32.7 mg kg^?1 higher than that in bulk soil after cultivation of soybean and maize for 80 days, which suggested that plant root exudates increased reduction of soil Mn oxides. Application of ammonium-N promoted reduction of Mn oxides in rhizosphere soil compared to application of nitrate and nitrate together with ammonium. Soybean cultivation led to a higher reduction in soil Mn oxides than maize cultivation. Application of single ammonium enhanced Mn uptake by the plants and led to more Mn accumulating in plant leaves, especially for soybean. Therefore, application of ammonium-based fertilizer can promote reduction of soil Mn oxides, while application of nitrate-based fertilizer can inhibit reduction of soil Mn oxides and thus reduce Mn²⁺ toxicity to plants.     

Nitrogen Availability for Maize from a Rolling Pampa Soil After Addition of Biosolids

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.     

Interaction of soil boron application with leaf B concentration,root length density,and canopy size of citrus affected by Huanglongbing

Abstract

Good and balanced citrus nutrition is important for high fruit yields and improved tree performance. A study was conducted for 2?years to investigate the effect of soil application of boron (B) on leaf nutrient content, canopy size, and root length density (RLD). The study was conducted on 10-year-old Candidatus Liberibacter asiaticus (CLas)-infected Vernia sweet orange on Rough Lemon rootstock in a commercial grove east of St. Cloud, FL planted at 375 trees ha^?1 on a traditional soluble dry nutrition and spray programs. Treatments were supplied with various ground-applied controlled-release fertilizer treatments containing B. Boron was applied at 0×, 2×, and 4× current University of Florida recommendation where 1×?=?1.12?kg ha^?1. Data collected included leaf B nutrient content, soil B concentration, trunk diameters, canopy volumes, soil electrical conductivity, and soil pH. The 0×, 2×, and 4× application rates corresponded with leaf nutrient contents ranging from 56?mg kg^?1 and 88?mg kg^?1 in March 2017, 162?mg kg^?1 and 288?mg kg^?1 in September 2017, and 122?mg kg^?1 and 320?mg kg^?1 in May 2018. Temporary, RLD decreased with time from March to September 2017 by 13, 30, and 37% at the 0, 2.24, and 4.48?kg B ha^?1 and increased by 309, 258, and 306% at the 0, 2.24, and 4.48?kg B ha^?1, respectively, from September 2017 to May 2018. No consistent pattern was established between soil B application with canopy size.     

Potassium fertilization and soil diagnostic criteria for forage corn (Zea mays L.) production contributing to lower potassium input in regional fertilizer recommendation

Abstract

Effective soil diagnostic criteria for exchangeable potassium (Ex-K) combined with inorganic potassium (K) application rates were developed to lower K input in forage corn (Zea mays L.) production using experimental fields with different application rates and histories of cattle manure compost. Two corn varieties, ‘Cecilia’ as a low K uptake variety and ‘Yumechikara’ as a high K uptake variety, were selected from among 20 varieties and tested to make diagnostic criteria for K fertilization applicable to varieties with different K uptakes. The K uptakes increased from 96 to 303 kg K ha^?1 for ‘Cecilia’ and from 123 to 411 kg K ha^?1 for ‘Yumechikara’ with increasing Ex-K content on a dry soil basis from 0.11 to 0.92 g kg^?1 with no inorganic K fertilizer application. The K uptake by corn for achieving the target dry matter yield of 18 Mg ha^?1 was estimated to be approximately 200 kg K ha^?1 in common between the two varieties. Yields of both varieties achieved the target yield at an Ex-K content of approximately 0.30 g kg^?1 with no K fertilization, although ‘Yumechikara’ reached the target yield at a lower Ex-K content. At the low Ex-K content of 0.1 g kg^?1, inorganic K fertilizer application at 83 kg K ha^?1 was needed to gain the target yield, and apparent K recovery rate for K fertilizer was calculated to be 70% for both varieties. The K uptakes for gaining the target yield by the K fertilization were lower than that by soil K supply. Based on these results, diagnostic criteria of Ex-K and inorganic K application rates were set up as follows: at an Ex-K content of < 0.15 g kg^?1, inorganic K fertilizer is applied at 83 kg K ha^?1 (100 kg ha^?1 as potassium oxide (K₂O) equivalent); at an Ex-K content of 0.15–0.30 g kg^?1, the application rate is reduced to 33 kg K ha^?1 (40 kg K₂O ha^?1); at an Ex-K content of ≥ 0.30 g kg^?1, inorganic K fertilizer is not applied because of sufficient K in the soil. Additionally, we propose that cattle manure compost be used to supplement soil K fertility.     

Soil Phosphorus Management Based on the Agronomic Critical Value of Olsen P

Fertilizer phosphorus (P) is generally added to agricultural soils to meet the needs of crop production. In this study, the crop yield and soil Olsen P were measured every year (5–18 years) at 16 winter wheat (Triticum aestivum L.) –maize (Zea mays L.) crop rotation sites in cinnamon soil (Luvisols in FAO system). The mean agronomic critical value of Olsen P for maize was 14.2 mg kg^?1 and for winter wheat was 14.4 mg kg^?1 when using the Liner-plateau and Mitscherlich models. The change in soil Olsen P was positively linearly correlated with the P budget (P < 0.01), and an increase of 4.70 mg kg^?1 in soil Olsen P for each 100 kg ha^?1 of P budget in the 0–20 cm soil layer. A model of P fertilizer recommendation rate that integrated values of the change in soil Olsen P in response to P budget and the agronomic critical value of Olsen P was used, in order to adjust current levels of soil Olsen P to the agronomic critical value at the experimental sites over the next 5 years, P fertilizer application rate should be in the range of 0–87.5 kg P ha^?1.     

Effect of Deficit Irrigation and Dairy Manure on Winter Wheat Yield,Soil Physical Health,and Nitrate Leaching

ABSTRACT

The effect of deficit irrigation (DI) on wheat crop yield, soil physical parameters and on nitrate nitrogen movement in soil profile was evaluated under application of dairy manure and nitrogen fertilizer. Two levels of DI were taken as I_0.6 (60% FC) and I_0.8 (80% FC) along with two dairy manure levels (20 and 25 Mg ha^?1) and three nitrogen levels (80, 100, and 120 kg ha^?1). The grain yield was high under I_0.8 than I_0.6, whereas the irrigation level has no significant effect on soil organic carbon contents. Dairy manure, irrigation, and nitrogen indicated strong interaction with each other for all yield-related parameters during both years of study, however, results for 2nd year were highly positive. Soil nitrate nitrogen movement was significantly affected under I_0.8 with high rate of dairy manure (25 Mg ha^?1) and nitrogen fertilizer (120 kg ha^?1). Results concluded that combined application of dairy manure (25 Mg ha^?1) and nitrogen fertilizer (120 kg ha^?1) under DI level I_0.8 resulted in high grain yield. To overcome water scarce conditions, further experiments can be designed by addition of various organic matters in different combination that enhances the yield and soil health.     

Fate of fertilizer nitrogen applied to grassland. I. Field leaching results

Results are presented from a 3 year investigation into nitrate leaching from isolated 0.4 ha grassland plots fertilized with 250, 500 and 900 kg N ha^?1 a^?1. Cumulative nitrate leaching over the 3 years was equivalent to 1.5%, 5.4% and 16.7% of the fertilizer applied at 250, 500 and 900 kg N ha^?1 rates respectively. Over a whole drainage season, mean nitrate leachate concentrations at 250 kg N ha^?1 did not exceed 4 mgl^?1, although maximum values of 13.3 mgl^?1 were observed. In contrast, at 900 kg N ha^?1, the mean nitrate leachate concentration in two of the years exceeded 90 mgl^?1. Mineral nitrogen balances constructed for the 1979 growing season indicated that leaching at 250 kg N ha^?1 was low because net mineralization of soil organic nitrogen was small, and crop nitrogen uptake almost balanced fertilizer application. Although the pattern of nitrate leaching suggested that by-passing occurred in the movement of water down the soil profile, it was not possible to confirm this using simulation models of leaching. Possible reasons for this, including the occurrence of rapid water flow down gravitationally drained macropores, are discussed.     

Lowland Rice Response to Thermophosphate Fertilization

Abstract

Use of adequate rates of phosphorus (P) in crop production on high‐P‐fixing acid soils is essential because of high crop response to P fertilization and the high cost of P fertilizers. Information on lowland rice response to thermophosphate fertilization grown on Inceptisols is limited, and data are also lacking for soil‐test‐based P fertilization recommendations for this crop. The objective of this study was to evaluate response of lowland rice to added thermophosphate and to calibrate P soil testing for making P fertilizer recommendations. A field experiment was conducted for two consecutive years in central Brazil on a Haplaquept Inceptisol. The broadcast P rates used were 0, 131, 262, 393, 524, and 655 kg P ha^?1, applied as thermophosphate Yoorin. Rice yield and yield components were significantly increased with the application of P fertilizer. Average maximum grain yield was obtained with the application of 509 kg P ha^?1. Uptake of macro‐ and micronutrients had significant quadratic responses with increasing P rates. Application of thermophosphate significantly decreased soil acidity and created favorable macro‐ and micronutrient environment for lowland rice growth. Across 2 years, soil‐test levels of Mehlich 1–extractable P were categorized, based on relative grain yield, as very low (0–17 mg P kg^?1 soil), low (17–32 mg P kg^?1 soil), medium (32–45 mg P kg^?1 soil), or high (>45 mg P kg^?1 soil). Similarly, soil‐test levels of Bray 1–extractable P across 2 years were very low (0–17 mg P kg^?1 soil), low (17–28 mg P kg^?1 soil), medium (28–35 mg P kg^?1 soil), or high (>35 mg P kg^?1 soil). Soil P availability indices for Mehlich 1 extractant were slightly higher at higher P rates. However, both the extracting solutions had highly significant association with grain yield.     

Effect of drip fertigation system on nitrate control in spinach Spinacea oleracea L.

(pp. 9–16)

Nitrate is a major form of uptake and storage of nitrogen for upland plants. However, nitrate is harmful to human health · ingestion of a large quantity can lead to cancer or methemoglobinemia. The effectiveness of drip fertigation for reducing nitrate in spinach was investigated in this study. Fertilizer application can be controlled effectively by drip fertigation. Field experiments were conducted in September 2002 and June 2003 at the National Agricultural Research Center for Hokkaido Region. Two spinach cultivars were grown in each cultivation in a plastic greenhouse, and the plants were treated with 4, 8 or 12 g N m^?2 of fertilizer applied by drip fertigation, and with 8, 12 or 16 g N m^?2 of fertilizer applied as basal application. The nitrogen was applied at the rate of 0.15 g m^?2 per day for the first 15 days, and 0.25 g m^?2 for the following 23 days in 8 g N m^?2 treatment of drip fertigation.

The rate of growth and nitrogen absorption of spinach in the early growth stages was very slow, but they increased quickly from around day 23 after sowing. The amount of nitrogen absorbed by spinach was close to the amount applied in 8 g N m^?2 treatment. This treatment resulted in spinach with a low nitrate concentration without reduction in yield. Although the same results were obtained by treatment with 8 g N m^?2 of fertilizer by basal application, there was a tendency for nitrate concentration to fall further with drip fertigation. The rate of nitrate-nitrogen to total-nitrogen rose sharply when the total-nitrogen concentration was higher than 42 g kg^?1 DW in leaf blade and 18 g kg^?1 DW in leaf petiole. The total-nitrogen concentration was lowered a little and for that reason the rate of nitrate-nitrogen to total-nitrogen was lower in spinach treated with 8 g N m^?2 of drip fertigation than in spinach treated with 8 g N m^?2 of basal application. Thus, drip fertigation was considered to reduce nitrate more stably.     

A Correlation of Rapid Cardy Meter Sap Test and ICP Spectrometry of Dry Tissue for Measuring Potassium (K+) Concentrations in Pak Choi (Brassica Rapa Chinensis Group)

Nutritional status of vegetable crops is often monitored by analysis of dried plant tissues, which is costly and often time consuming. Two greenhouse trials were conducted, at the University of Hawaii at Manoa, Magoon facilities, to evaluate the portable cardy ion meter (CIM) in determining potassium (K⁺) status in fresh petiole sap of pak choi as compared with standard laboratory methods. In the first greenhouse trial, three algae species (Gracilaria salicornia, Kappaphycus alvarezii, and Eucheuma denticulatum) were used to apply five rates of K⁺ (0, 84, 168,252, and 336 kg.ha^?1). The pak choi was directly seeded into 4 L pots and was grown in peat moss. In the second greenhouse trial, K+ was provided through Eucheuma denticulatum and potassium nitrate (KNO₃) at five rates (0,112, 168, 224, 280, and 336 kg.ha^?1) in peat moss and soil media. At harvest, K⁺ concentrations in fresh petiole sap were analyzed immediately with CIM and the dried samples were analyzed by inductively coupled plasma spectroscopy (ICP) measurement. The results showed increase in leaf K+ content at higher rates and the maximum concentration of leaf K⁺ at 4500–5300 mg/L for sap and 8–9% for tissue was obtained when K⁺ was provided between 224 and 284 kg.ha^?1. There was a close correlation between the CIM readings and the ICP method (r = 0.8048 and 0.8314) from the first and second GH results, respectively. The results suggest that the CIM could be used for the rapid monitoring of the relative K⁺ status of plants. The data further suggested 4500–5000 mg K/L for fresh petiole sap and 7.5% K⁺ in tissue as critical levels for K⁺ concentration in pak choi.