Nitrogen‐Supplying Capacity of Soils for Rice and Wheat and Nitrogen Availability Indices in Soils of Northwest India

Abstract

Quantitative assessment of soil nitrogen (N) that will become available is important for determining fertilizer needs of crops. Nitrogen‐supplying capacity of soil to rice and wheat was quantified by establishing zero‐N plots at on‐farm locations to which all nutrients except N were adequately supplied. Nitrogen uptake in zero‐N plots ranged from 41.4 to 110.3 kg N ha^?1 for rice and 33.7 to 123.4 kg N ha^?1 for wheat. Availability of soil N was also studied using oxidative, hydrolytic, and autoclaving indices, salt‐extraction indices, light‐absorption indices, and aerobic and anaerobic incubation indices. These were correlated with yield and N uptake by rice and wheat in zero‐N plots. Nitrogen extracted by alkaline KMnO₄ and phosphate borate buffer and nitrogen mineralized under aerobic incubation were satisfactory indices of soil N supply. For rice, 2 M KCl and alkaline KMnO₄ were the best N‐availability indices. Thus, alkaline KMnO₄ should prove a quick and reliable indicator of indigenous soil N supply in soils under a rice–wheat cropping system.     

Nitrogen and mineral composition of autumn‐grazed pasture

Abstract

Grazing management in autumn can influence the botanical composition and productivity of a sward. Cycling of nutrients as a result of grazing livestock activity and variable canopy growth rates may influence mineral nutrient supply and demand in a dynamic canopy. An experiment was conducted to determine the influence of autumn grazing practices on the growth and composition, including minerals in terms of ruminant requirements, of a grass/legume sward. Paddocks were established and three replicates grazed by growing lambs for 30‐, 60‐, or 90‐d intervals beginning in late summer. Herbage samples were collected at the beginning of the grazing interval and at the end of each interval (closing date). Herbage mass, and nitrogen (N), phosphorus (P), potassium (K), magnesium (Mg), calcium (Ca), and sulfur (S), as well as copper (Cu) and zinc (Zn) were examined in terms of the influence of sampling date, closing date, year, and the interaction of these factors from stockpiled and grazed canopies. Soil mineral composition was determined as well. Concentrations of all minerals declined with increasing soil depth and P, Na, Mg, and Ca increased in soil over the course of the experiment. Soil N concentration was reflected in the pattern of herbage growth in autumn. In general, closing date had no influence on herbage mineral composition and concentrations were within the recommended levels for a range of livestock. Phosphorus was the exception and concentrations in herbage were low in terms of requirements for high producing livestock such as lactating dairy cattle. Uptake or mineral reallocation within the plant remained constant during the autumn growth interval, since mineral yields were stable as growth rates declined in 1991 and increased when growth rates were stable in 1992. Mineral related nutritional problems in grazed mixed‐species pasture, would most likely be a function of mineral bioavailability or interactions, rather than low concentrations in the herbage.     

Direct Estimation of Nitrogen Gases Emitted from Flooded Soils During Denitrification of Applied Nitrogen

Denitrification losses measured by direct method (measuring the evolution of (N2 N2O)-^15N) were compared with the apparent denitrification losses (calculated from the difference between the total N loss and ammonia loss), for fertilizers applied to flooded soils.The direct measured denitrification losses from potassium nitrate were 23.0%,40.0%,and 63.1-79.7% of applied N in rice field,and in incubations of 7 cm deep layer of soil and 2 cm deep layer of soil,respectively;while the corresponding apparent denitrification losses were 96.0%,98.4%,and 97.7-97.9%,respectively.In field experiments with urea,the direct measured denitrification losses ranged from 0.1-1.8%,which were much less than the apparent denitrification losses (41.3-45.7%).Such discrepancies were primarily due to the entrapment of the gaseous products of denitrification in the soil as revealed by the facts:(1) stirring the floodwater and the surface soil markedly increased the fluxes of (N2_N2O)-^15N from urea or potassium nitrate applied to the flooded rice field,and (2) reducing the pressure in the headspace of the incubation bottle with the 7 cm soil layer during gas sampling decreased the discrepance between the direct measured and apparent denitrifecation losses from 58.4% to 21.2%.The advantage of reducing the pressure in the headspace is that there is minimal disturbance of the soil.Further testing of this technique in rice field is needed to determine its effectiveness in releasing the entrapped gaseous products of denitrification so that denitrification losses can be quantified directly.     

Effect of Incorporation of Wheat Straw and Urea into Soil on Biomass Nitrogen and Nitrogen-Supplying Characteristics of Paddy Soil

Pot experiments were carried out to study the effect of incorporation of wheat straw and/ or urea into soil on biomass nitrogen and mineral nitrogen and its relation to the growth and yield of rice.The combined appliation of wheat straw and urea increased much more biomass nitrogen in soil than the application of wheat straw or urea alone and consequently increased the immobilization of urea nitrogen added and reduced the loss of urea nitrogen.An adequate nitrogen-supplying process to rice plant could be obtained if C/ N ratio of the material added was about 20.The three yield components of rice were affected significantly by the status of nitrogen supplying.More than 30mg N/ kg soil of mineral nitrogen at effective tillering stage,panicle initiation stage and filling stage should be maintained in order to get high rice yield,though the criteria varied with the different experimental conditions.     

Boiling Potassium Chloride–Extractable Nitrogen as an Index of Potentially Mineralizable and Plant‐Available Nitrogen in Soil

Abstract

Mineralization of soil organic nitrogen (N) and its contribution toward crop N uptake is central to developing efficient N‐management practices. Because biological incubation methods are time consuming and do not fit into the batch‐analysis techniques of soil‐testing laboratories, an analytical procedure that can provide an estimate of the mineralizable N would be useful as a soil‐test method for predicting plant‐available N in soil. In the present studies, the ability of boiling potassium chloride (KCl) to extract potentially mineralizable and plant‐available N in arable soils of semi‐arid India was tested against results from biological incubations and uptake of N by wheat in a pot experiment. Mineralization of organic N in soils was studied in the laboratory by conducting aerobic incubations for 112 days at 32°C and 33 KPa of moisture. Cumulative N mineralization in different soils ranged from 8.2 to 75.6 mg N kg^?1 soil that constituted 2.7 to 8.8% of organic N. The amount of mineral N extracted by KCl increased with increase in length of boiling from 0.5 to 2 h. Boiling for 0.5, 1, 1.5, and 2 h resulted in an increase in mineral‐N extraction by 9.3, 12.7, 19.6, and 26.1%, respectively, as compared to mineral N extracted at room temperature. The boiling‐KCl‐hydrolyzable N (ΔN_i) was directly dependent upon soil organic N content, but the presence of clay retarded hydrolysis for boiling lengths of 0.5 and 1 h. However, for boiling lengths of 1.5, and 2 h, the negative effect of clay was not apparent. The ΔN _i was significantly (P=0.05) correlated to cumulative N mineralized and N‐mineralization potential (N₀). The relationship between N₀ and ΔN _i was curvilinear and was best described by a power function. Boiling length of 2 h accounted for 78% of the variability in N₀. Results of the pot experiment showed that at 21‐ and 63‐day growth stages, dry‐matter yield and N uptake by wheat were significantly correlated to boiling‐KCl‐extractable mineral N. Thus, boiling KCl could be used to predict potentially mineralizable and plant‐available N in these soils, and a boiling time of 2 h was most suitable to avoid the negatively affected estimates of boiling‐KCl‐hydrolyzable N in the presence of clay. The results have implications for selecting length of boiling in soils varying widely in clay content, and this may explain why, in earlier studies, longer boiling times (viz. 2 or 4 h) were better predictors of N availability as compared to 0.5 and 1 h.     

Natural Nitrogen-15 Abundance of Ammonium Nitrogen and Fixed Ammonium in Soils

The present article deals with the natural nitrogen-15 abundance of ammonium nitrogen and fixed ammonium in different soils.Variations in the natural ^15N abundance of ammonium nitrogen mineralized in soils under anaerobic incubation condition were related to soil pH.The δ ^15N of mineralizable N in acid soils was lower but that in neutral and calcareous soils was higher compared with the δ ^15N of total N in the soils.A variation tendence was also found in the δ ^15N of amino-acid N in the hydrolysates of soils.The natural ^15N abundance of fixed ammonium was higher than that of total N in most surface soils and other soil horizons,indicating that the increase of δ ^15N in the soil borizons beneath subsurface horizon of some forest soils and acid paddy soils was related to the higher δ ^15N value of fixed ammonium in the soil.     

Effects of Slow‐Release Fertilizers on Tomato Growth and Nitrogen Leaching

Tomatoes (Lycopersicon esculentum Mill.) were grown in 9.46‐L plastic pots in a glasshouse for evaluation of their growth and nitrogen (N) losses through leaching. Plants were fertilized with either ammonium nitrate (AN) or one of three slow‐release N fertilizers. The slow‐release N fertilizers were Georgia Pacific liquid 30‐0‐0 (L30), Georgia Pacific granular 42‐0‐0 (N42), and Georgia Pacific granular 24‐0‐0 (N24). Each fertilizer was applied at 112 low N rate (L) and 224 high N rate (H) kg N ha^?1. The pots were filled with either a sandy soil from Florida or a loam soil from Georgia. Increasing the N rate did not influence shoot biomass at 19 days after transplanting (DAT) and increased biomass production at 77 DAT. Shoot biomass differed significantly among fertilizer treatments. The accumulation of N in shoots was significantly influenced by fertilizer source, rate, and soil type. The plants grown in the loam soil accumulated significantly more N than those grown in the sandy soil with the same treatment. In the loam soil, the highest and lowest N accumulations occurred in the N42‐H and N24‐L treatments, respectively; and in the sandy soil the corresponding treatments were AN‐H and N24‐L. The amount of N leached varied with the different fertilizers, soils, and time. The net leaching of N ranged from ?0.4% to 6.3% of the fertilizer N applied for the loam soil and 6.5% to 32.9% for the sand soil. The net amount of N leached from the loam soil at both high and low application rates declined in the following order: AN > N24 > N42 > L30; the corresponding order for the sandy soil was AN‐H > N42‐H > L30‐H > N24‐H. L30 had the least leaching potential, and ammonium nitrate had the most. Slow‐release fertilizers had significantly less leaching N than did ammonia nitrate.     

Nutritional Evaluation of Nitrogen and Potassium Fertilization of Carob Tree under Dry‐Farming Conditions

Abstract

The aim of this work was to assess how potassium (K) and nitrogen (N) fertilization might affect the variation of leaf and fruit nutrient concentrations in carob tree (Ceratonia siliqua L.) under low precipitation. A field study was conducted in 1997, 1998, and 1999 in a calcareous soil. Four fertilization treatments were tested: no fertilizer (C), 0.8 kg N tree^?1 (N treatment), 0.83 kg K tree^?1 (K treatment), and 0.80 kg N tree^?1 plus 0.83 kg K tree^?1 (NK treatment). During the hydrological cycle 1998/1999, only 250 mm of rain were recorded. Because of this, from 1998 to 1999 a decrease in the concentrations of mobile nutrients N, phosphorus (P), and K and an increase in calcium (Ca), iron (Fe), and manganese (Mn) were observed in leaves. The application of N led to higher leaf N concentration compared with other treatments. This response allowed the establishment of a linear model that relates soil plant analysis development (SPAD) readings with leaf N concentrations (r²=0.55; P<0.05). Compared with leaves, fruits showed similar amounts of N and P; less Ca, Mg, Fe, and Mn; and high concentrations of K. Fertilization did not change considerably the mineral composition of fruits, and because of large variation among trees, yield was similar for all treatments.     

Nitrogen Fertilizer Influences Fruit Quality,Soil Nutrients and Cover Crops,Leaf Color and Nitrogen Content,Biennial Bearing and Cold Hardiness of ‘Golden Delicious’

Four rates of ammonium nitrate (NH₄NO₃) (0, 151, 454, and 908 g actual N/tree) were applied each spring for 6 years to ‘Golden Delicious’ (Malus domestica) apple trees. High rates of nitrogen (N) increased N concentration of Orchardgrass (Dactylis glomerata) blades and increased cover-grass growth whereas various legume species were prevalent at the low rates. Leaf N in spur or mid-terminal leaves increased yearly, and was related to leaf color by visual comparison and reflectance. Fruit from the higher N rates had greener peel and lower firmness, soluble solids content and titratable acidity. In vitro freeze tests indicated trees fertilized with lower rates of N were more cold hardy during the fall, winter and spring than those receiving the higher rates. In a similar long-term study on ‘Delicious,’ cold hardiness was related not only to seasonal temperature cycles and shoot dry matter, but to total sugars and sorbitol content in wood or sap.     

Nitrogen and organic matter of volcanic ash soils of Santa Bárbara Association in Chile

Santa Bárbara association is a group of Andosols widely distributed on the western foothills of the Andes Mountains in the Central Valley of Chile from about 36° to 40° south latitude. The soils of this association may be divided into two groups—south and north—by the characteristics of soil organic matter, although they are much alike in morphology. The line of demarcation between the groups lies at about 38° south latitude.

The potential nitrogen fertility or , the content of easily decomposable organic nitrogen is greater in the south soils than in the north soils of which humic matter is at a more advanced stage of humification, as compared with that of the south soils. Dry summers have caused the north soils to lessen in their potential nitrogen fertility and to stimulate humification of organic matter, altering the organic matter in quantity as well as in nature. It is evident that the analysis of soil organic matter is an effectual measure for the characterization of Andosols, and hence for the classification of the soils.

It is very probable that a considerable water erosion has occurred in the soils of this association, transporting the fine soil particles from the mid-slope to the foot of the hills.     

Nitrogen fertigation of greenhouse‐grown tomato

Abstract

This greenhouse study was conducted to determine the response of trickle‐irrigated tomato (Lycopersicon esculentum cv. Dombo) to 6.4, 12.8, or 19.2 mmol N/L applied via the irrigation stream. The plants were grown in pots filled with 12 kg of soil. The amount of N applied in a total of 438 L of water per plant was 39.4, 78.8, or 118.2 g for the three N levels, respectively. The residual NO₃‐N concentration in the root volume was negligible with the 6.4 mmol N/L treatment, whereas, with the highest N level increased sharply for the first 16 weeks before reaching a value around 32 mmol N/L, which continued for the remainder of the experiment. With the highest N level there was also increase of soil solution EC, and NO₃‐N concentration in laminae and petioles was in excess. With the lowest N treatment, NO₃‐N concentration in laminae and petioles was at deficient levels. With 12.8 mmol N/L, NO₃‐N in petioles and laminae was at the sufficient level and yet no substantial increase of soil solution EC or NO₃‐N concentration occurred, suggesting efficient use of N by crop. The highest yield (12.6 kg marketable fresh fruit per plant) was obtained with 12.8 mmol N/L due to increased number of fresh weight of fruits. It was concluded that 12.8 mmol N/L applied via the irrigation stream is adequate for high tomato yield without unduly raising soil salinity or wasting fertilizer N.     

Estimation of Plant‐Available Nitrogen in Soils using Rapid Chemical and Biological Methods

The relationships between potential laboratory indices for plant‐available nitrogen (N) and the plant N uptake in a pot experiment with ryegrass were assessed for 13 mineral soils and 2 peat soils. The methods included aerobic soil incubation, soil incubation in a bioreactor, hot potassium chloride (KCl)–extractable mineral N, 0.01 M calcium chloride (CaCl₂)–extractable N, and N loss at heating. The indices for total plant‐available N accounted for 63–93% of the variance in N uptake in a statistical analysis with all soils (n = 15) and 27–89% for the mineral soils (n = 13). Most indices were not a direct quantitative measure of the plant N uptake. The N mineralization indices accounted for 57–86% of the variance in N mineralization for all soils and 5–50% for the mineral soils. Hot KCl‐extractable mineral N and 0.01 M CaCl₂–extractable N were the most promising rapid indices for plant‐available N.     

Nitrogen for no‐tillage corn in Virginia: Sources and time of application

Abstract

No‐tillage corn (Zea mays L.) culture normally entails the placement of N fertilizer on the soil surface without mechanical incorporation. This field investigation was conducted to compare the N fertilizers that are most widely used in Virginia, when applied in this manner, for their effectiveness in producing notillage corn. Comparisons of the time of applying NH₄NO₃ were also made. Grain and stover yields, in addition to N removed in the crop, were used to draw conclusions. The experiments were conducted on both fertile and infertile soils in 1972 and 1973, both of which were relatively wet years. The fertilizers tested, urea, NH₄NO₃, and N solutions, were equally effective, per unit of N applied. Split applications of NH₄NO₃ showed no statistically significant advantage over all applied at planting but slightly trended to do so. N deficiency reduced grain yields relatively more than stover yields.     

Mineralization and Transformation of Nitrogen Derived from Plant Materials in Soils over 10 Years

Results of a 10-year decomposition experiment indicated that the annual mineralization rate of organic N in newly-formed humus varied with the type of original plant materials and the water regimes for decomposition,ranging from 0.028 to 0.074.The mineralization rate under waterlogged conditions was higher than that under upland conditions.The proportion of α-amino acid N in humus newly-formed under waterlogged conditions was slightly higher than that under upland conditions.It decreased gradually with time,while the proportion of nonhydrolyzable N showed no consistent trend,irrespective of the water regines for decomposition.The distribution of amino acids in humus newly-formed from different plant materials under various water regimes was quite similar with that in original plant materials,and only minor differences could be found among them.For example,in comparison to original plant materials,the newly-formed humus contained higher proportions of isoleucine,cysting,γ-amino-butyric acid and ornithine,and lower proportions of phenylalanine and proline.Moreover the proportion of phenylalanine was higher in the humus newly-fored under waterlogged conditions than that under upland conditions.     

Nitrogen,phosphorus, and potassium effects on pre‐ and post‐transplant growth of salvia and vinca seedlings

Pre‐ and post‐transplant growth of bedding plants is affected by seedling nutrition. However, there is little information available on how seedling nutrition affects the growth of ornamental bedding plants. In this study, we quantified the effects of nitrogen (N) (8 to 32 mM) and phosphorus (P) and potassium (K) concentration (0.25 to 1 mM) of the seedling fertilizer on pre‐ and post‐transplant growth and nutrient element content of salvia (Salvia splendens F. Sellow ex Roem. & Schult.) and vinca (Catharanthus roseus L.) seedlings. Shoot growth of salvia and vinca increased with increasing concentrations of N in the pre‐transplant fertilizer and these differences lasted until the end of the study at 15 days after transplanting. Pre‐transplant root dry mass of these species was not affected by the N concentration of the fertilizer, but root dry mass at 12 days after transplanting was positively correlated with the N concentration of the pre‐transplant fertilizer. Increasing N concentrations in the seedling fertilizer increased tissue N levels of salvia and decreased tissue K level of vinca at transplanting. Increasing P and K concentrations in the pre‐transplant fertilizer increased tissue P level of salvia and P and K levels of vinca, but had little effect on seedling growth. Leaf area and root dry mass at transplanting decreased slightly with increasing P and K concentration in the fertilizer. There were no lasting effects of pre‐transplant P and K concentration of the fertilizer. These results indicate that salvia and vinca seedlings can benefit from high concentrations of N (up to 32 mM) in the fertilizer, while only low concentrations of P and K (0.25 mM) are needed.     

Impact of Postharvest Sprays of Nitrogen,Boron and Zinc on Nutrition,Reproductive Response and Fruit Quality of ‘Schattenmorelle’ Tart Cherries

The aim of the study was to examine effects of fall sprays of nitrogen (N), boron (B) and zinc (Zn) on nutrition, reproductive response, and fruit quality of tart cherry (Prunus cerasus L.). The experiment was conducted during 2008–2010 in Poland on mature ‘Schattenmorelle’ sour cherry trees, planted at a spacing of 4.0 × 1.5 m on a coarse-textured soil with low level of organic matter, and adequate reaction and availabilities of macro- and micronutrients. Tart cherries were sprayed with boric acid-B, ethylenediaminetetraacetic acid (EDTA)-Zn, and urea-N at 40–50 d prior to initiation of leaf fall according to following schema: (i) spray of N at a rate of 23 kg ha^?1; (ii) spray of B and Zn at doses of 1.1 kg ha^?1 and 0.5 kg ha^?1, respectively; and (iii) spray of N, B, and Zn at the same rates as in the above spray combinations. The trees sprayed with water were served as the control. The results showed that postharvest spray treatments had no effect on defoliation, cold damage of flower buds, fruit set, yielding, plant N status, mean fruit weight, and soluble solids concentration in fruit. Postharvest sprays of B and Zn with or without N enhanced status of Zn and B in fall leaves, and B in flowers but had no impact on levels of the above micronutrients in summer leaves. Leaf-absorbed B was withdrawn in the fall, whereas Zn was immobile. It is concluded that postharvest B sprays can be recommended to increase B status in flowers of tart cherry, whereas fall sprays of urea-N and Zn are not able to improve plant nutrition of those nutrients the following season.     

Soil Total Nitrogen and Natural 15Nitrogen in Response to Long-Term Fertilizer Management of a Maize–Wheat Cropping System in Northern China

The Fengqiu long-term field experiment was established to examine effects of organic manure and mineral fertilizers on soil total nitrogen (N) and natural ¹⁵N abundance. Fertilizer regimes include organic manure (OM), one-half N from organic manure plus one-half N from mineral N fertilizer (1/2OMN), mineral fertilizers [N–phosphorus (P)–potassium (K), NP, NK, PK], and a control. Organic manure (OM and 1/2OMN) significantly increased soil total N and δ¹⁵N, which was expected as a great amount of the N applied remained in soils. Mineral NPK fertilizer and mineral NP fertilizer significantly increased total N and slightly increaed δ¹⁵N. Phosphorus-deficient fertilization (NK) and N-deficient fertilization (PK) had no effect on soil total N. Significantly greater δ¹⁵N was observed in the NK treatment as compared to the control, suggesting that considerable N was lost by ammonia (NH₃) voltalization and denitrification in this P-deficiency fertilization regime.     

Growth and Accumulation of Nitrogen and Potassium in Flue‐Cured Tobacco as Affected by Calcium Nitrate and Ammonium Nitrate

The process of biomass, nitrogen (N), and potassium (K) accumulation over time as affected by N forms is poorly understood. The objective of this study was to identify the effects of N form on growth as well as on N and K nutrition of flue‐cured tobacco plants (Nicotiana tobaccum L.). The plants were grown in a greenhouse with pots of soil for 117 days after 200 days of preculture. Three treatments (calcium nitrate [Ca(NO₃)₂], ammonium nitrate (NH₄NO₃), and ammonium nitrate plus straw (NH₄NO₃ + straw)) were used. The results showed that there were no significant differences in shoot dry mass of tobacco among the three treatments during the entire growth stage except at 30 and 117 days after transplanting. At these two growth stages, shoot biomass with the Ca(NO₃)₂ treatment was significantly less than that with NH₄NO₃ with or without straw. The NH₄NO₃ + straw plants had more mature leaves and greater leaf dry weight than the other two treatments. At an early stage (before 66 days), N concentration of Ca(NO₃)₂‐fed plants was less than with the other two treatments. The leaf K concentration and shoot K content of NH₄NO₃ and NH₄NO₃ + straw plants were more than with the Ca(NO₃)₂ treatment before maturity. Also, K concentration in mature leaves with these two treatments was greater than with Ca(NO₃)₂ treatment. All these results indicated that NH₄NO₃ application had benefits to the maturity and K accumulation in leaves of tobacco.     

Mitrification-Denitrification Loss of Added Nitrogen in Flooded RiceRhizosphere

Nitrification-denitrification losses of 15N-labelled nitrate and ammonium applied to the rhizos phere and nonrhizosphere of flooded rice were evaluated in 2 greenhouse rhizobox experiments.The loss of added N via denitrification was estimated directly by measuring the total fluxes of (N2O N2)12N,It was found that 67% and 51%-56% of 15N-nitrate added to rice rhizosphere were lost as (N2O N2)-15N in the 2 experiments,respectively,which were comparable to that added to norhizosphere soil(70%and 47%,respectively),implying that the denitrifying activity in rice rhizosphere was as high as that in nonrhizosphere soil.However,only trace amounts (0-0\3% of added N)were recovered as (N2O N2)-15N when 15N-ammonium was applied to either rhizosphere or nonrhizosphere,which seems to indicate that the nitrifying activity in the either rhizosphere of nonrhizosphere soils was quite low.The apparent denitrification calculated from 15N balance studies was 10%-47% higher than the total flux of (N2O N2)-15N.Reasons for the large differences can not be explained satisfactorily.Though the denitrifying activity in rhizosphere was high and comparable to that in nonrhizosphere soil.presumably due to the low nitrifying activity and /or the strong competition of N uptake against denitrification.the nitrification-denitrification taking place in rhizosphere could not be an important mechanism of loss of ammonium N in flooded rice-soil system.     

Effect of Straw Incorporation on 15N‐Labeled Ammonium Nitrogen Uptake and Rice Growth

Abstract

A greenhouse experiment was conducted to determine the effect of rice straw residue on growth and uptake of added ¹⁵N‐labeled ammonium nitrogen (NH₄‐N) (3% ¹⁵N abundance at the rate of 150 kg N ha^?) by rice in Crowley silt loam soil (Typic Albaqualfs). Higher rates of rice straw addition had an adverse affect on plant growth from the first to sixth week. After 6 weeks, the high rice straw treatment had a positive effect on plant growth (P<0.05). The ¹⁵N‐labeled ammonium or fertilizer nitrogen (N) uptake by rice was significantly lower (P<0.05) in the high rice straw treatment as compared to lower rice straw treatments. Greater plant growth was recorded under alternate flooding and draining condition as compared to continuously flooded treatment (P<0.01).