Influence of Azospirillum inoculation and nitrogen supply on grain yield,and carbon‐ and nitrogen‐assimilating enzymes in maize

Nitrogen (N) supply increased yield, leaf % N at 10 days after silking (DAS) and at harvesting, the contents of ribulose‐1,5‐bisphosphate carboxylase (RUBISCO) and soluble protein, and the activities of phosphoenolpyruvate carboxylase (PEPC), and ferredoxin‐glutamate synthase (Fd‐GOGAT), but not of glutamine synthetase (GS) for six tropical maize (Zea mays L) cultivars. Compared to plants fertilized with 10 kg N/ha, plants inoculated with a mixture of Azospirillum sp. (strains Sp 82, Sp 242, and Sp Eng‐501) had increased grain % protein, and leaf % N at 10 DAS and at harvest, but not grain yield. Compared to plants fertilized with either 60 or 180 kg N/ha, Azospirillum‐inoculated plants yielded significantly less, and except for GS activity, which was not influenced by N supply, had lower values for leaf % N at 10 DAS and at harvest, for contents of soluble protein and RUBISCO, and for the activities of PEPC and Fd‐GOGAT. Yield was positively correlated to leaf % N both at 10 DAS and at harvest, to the contents of soluble protein and RUBISCO, and to the activities of PEPC and Fd‐GOGAT, but not of GS, when RUBISCO contents and enzyme activities were calculated per g fresh weight/min. However, when enzyme contents and enzyme activities were expressed per mg soluble protein/min, yield was correlated positively to RUBISCO and PEPC, but negatively to GS. These results give support to the hypothesis that RUBISCO, Fd‐GOGAT, and PEPC may be used as biochemical markers for the development of genotypes with enhanced photosynthetic capacity and yield potential.     

Release and recovery of nitrogen from winter annual cover crops in no‐till corn production

Abstract

Soil bulk density markedly influences hydrolysis of surface‐applied granular urea that is vulnerable to serious ammonia volatilization losses. In order to decrease the ammonia losses by retarding urea hydrolysis, several chemicals have been tested for their soil urease inhibition properties. Phenyl phosphorodiamidate (PPDA) is a potent soil urease inhibitor. Laboratory studies using soil column incubations were conducted to investigate the effect of soil bulk density on inhibition of hydrolysis of surface‐applied urea granules (=20 mg of urea/granule) containing 1% PPDA in unsaturated soils. The increase in soil bulk density (from 0.69 to 1.50 Mg/m³) markedly increased the rate of hydrolysis of surface‐applied urea granules and significantly decreased the apparent urease inhibition by PPDA present in the granules. These results are attributed to the probable spatial separation of urea and PPDA because of the differences in diffusive transports in unsaturated soils caused in part by differences in their solubilities in water.     

Effects of normal and Fe‐treated organic matter on Fe chlorosis and yields of grain sorghum

Abstract

A greenhouse study was conducted to evaluate the effects of normal and Fe‐treated plant material on Fe chlorosis and yields of grain sorghum. Pigweed, guar, clover, sunflower and wheat plants grown in the field for six weeks were sprayed with a 20% ferrous sulfate solution. The plants were harvested after 48 hours, air dried, then ground to pass through a 0.5 mm stainless steel seive. Different rates of normal and Fe‐treated plant material (0, 14.8, 22.2 and 29.6 Mg ha^‐1) were added to the Pernitas fsl (Typic Agiustoll).

Chlorosis increased with increasing rates of normal plant material added to the soil. Conversely, applications of Fetreated plant material reduced Fe deficiency chlorosis in grain sorghum. The order of effectiveness of Fe‐treated plant material was: sunflower > pigweed > guar > clover > wheat. There was no significant growth response to the untreated plant material. Growth responses to the Fe‐treated plant material were: sunflower > pigweed > guar > wheat > clover. Data obtained indicate that sunflower and pigweed are good Fe‐carriers and could be used to recycle Fe in the soil to correct Fe deficiency chlorosis and increase yields     

Root development in potato and carrot crops – influences of soil compaction

Row crops such as potatoes (Solanum tuberosum L.) and carrots (Daucus carota L.) are of high economic value in the Nordic countries. Their production is becoming more and more specialized, including continuous arable cropping and heavier farm machinery, with increased risk of soil compaction. The result may be restricted root development and economic losses. Potatoes have widely branched adventitious roots, whereas carrots have taproots with fibrous roots extending from them. Under optimal soil conditions, total root length per surface area may reach more than 10 km m^?2 for both species. Maximal root depth is about 140 cm for potato and more than 200 cm in carrots. Most of the root mass is usually distributed within the upper 100 cm, whereof more than 50% may be deeper than 30 cm. Soil compaction causes a dense soil with few large pores, poor drainage and reduced aeration, especially in wet soils with low organic matter content and high proportions of silt or clay. With compacted subsoil layers, roots will be concentrated more in the upper layers and thus explore a smaller soil volume. This will lead to reduced water and nutrient uptake, reduced yields and low nutrient utilization efficiency. In this review article, we describe the interactions between root development and soil conditions for potatoes and carrots, with special focus on sub-optimal conditions caused by soil compaction. We also discuss the effects of tilling strategies, organic material, irrigation and fertilization strategies and controlled traffic systems on root and yield development. To reduce subsoil compaction there is a need to implement practises such as controlled traffic farming, new techniques for ploughing, better timing of soil operations, crop rotations with more perennial crops and supplements of organic material. Moreover, there is a need for a stronger focus on the impacts of farm machinery dimensions.     

Comparison of understorey biological nitrogen fixation and biomass production in grassed‐down conventional and organic apple orchards in Canterbury,New Zealand

Abstract

In a previous study, the understorey biomass production and biological nitrogen (N) fixation of a grassed‐down organic apple orchard were presented. The aim of this paper is to report the results of a similar study of two conventional orchards in a nearby location and to compare the present results with those of the organic orchard. Biological N₂ fixation was determined in the field using the ¹⁵N isotopic dilution technique and the experiments were conducted over a two‐year period. Present results showed that substantial amounts of N (112 to 143 kg N ha^‐1.2 years^‐1) were fixed in the understorey of the conventional orchard and these were not significantly different from those of the organic orchard. However, the N₂ fixation was sustained in the conventional, but not in the organic orchards in the second year, probably due to regular additions of fertilizers in the conventional orchards. In both orchards, N₂ fixation was better correlated with clover than total dry matter yield. Seasonal effects found were highest N₂ fixation and biomass production occurring during late spring and early summer and lowest during winter. Climatic factors were investigated in one of the conventional orchards and it was found that seasonal effects were related to a combination of temperature and moisture deficit effects.     

Studies of nitrogen immobilization and mineralization in calcareous soils—IV. Changes in the organic nitrogen of light and heavy subfractions of silt- and fine clay-size particles during nitrogen turnover

A calcareous clay nd a calcareous sand, were fractionated densimetrically by dispersion in organic liquids of sp. gr. 1.59–2.06. The N contents of the light fractions decreased with increasing densities of the suspending liquids and were up to 18–23 times higher than those of the whole soils. Light fraction organic-N of both the sandy and clay soils was obtained mainly from silt-size components. However, the efficiency, with which light fraction material was obtained from the two whole soils, varied. With the clay soil, the total yield of light fraction organic-N was increased markedly by applying the densimetric technique to particle size components, rather than to the whole soil.Silt-size and fine clay-size particles from soils, sampled during rapid metabolism of microbial organic-[¹⁵N], were further fractionated densimetrically in “Nemagon”, sp. gr. 2.06. The organic-[¹⁵N] of the light and heavy subtractions changed markedly (P < 0.05) during periods of net ¹⁵N immobilization and mineralization, including a period after soil fumigation when extensive decomposition of [¹⁵N]-labelled microbial biomass occurred. Changes in the ¹⁵N of complementary light and heavy subfractions followed similar trends. Light subtraction organic-[¹⁵N] usually showed the greater relative change but the differences between the subtractions were not statistically significant. It is concluded that when small proportions only of soil organic-N are associated with macroorganic debris, as in these two soils amended wth glucose and ¹⁵NO^?₃, densimetric fractionation at a sp. gr. as high as 2.06 will yield light and heavy fractions, whose nitrogenous components are similarly available to biological attack. Enhanced metabolism of light fraction material is more likely to be demonstrated when such material consists mainly of obvious plant residues, and this may be more easily achieved by fractionation in liquids of sp. gr. <2.     

Extraction of soil nitrogen by chloroform fumigation – A new index for the evaluation of soil nitrogen supply

The N extracted after chloroform (CHCl₃) fumigation was determined as a possible index of soil N supply to plants. The relationships between extractable N following fumigation and reference indices such as total N, alkali-hydrolyzable N, N released by the Stanford short-term incubation method, and the N extracted by KCl and by CaCl₂, were measured in nine soils of differing soil N supply capacity. A highly significant correlation was achieved between the extractable N released by fumigation and the N released by the Stanford method, i.e. a short-term aerobic incubation (r = 0.87). Similarly, the correlation between extractable N by fumigation and the N uptake by ryegrass was highly statistically significant (r = 0.93). Using the N extracted following fumigation has the advantage that laboratory results are available in two days and are both reproducible and of high precision. Therefore, the N extracted following fumigation is a valid, timesaving and precise index of soil N supply capacity.     

Determination of dissolved organic nitrogen using persulfate oxidation and conductimetric quantification of nitrate‐nitrogen

Abstract

Nitrogen (N) in forest soil extracts and surface waters may be dominantly in organic compounds as dissolved organic nitrogen (DON). Due to various difficulties associated with measuring total N (as TKN) by the Rjeldahl digest, this important vehicle for nutrient movement is rarely monitored. By coupling two relatively new methods and optimizing them for use in soil studies, we developed an alternative method for measuring DON. Analysis of pure compounds and field samples shows that persulfate oxidation combined with conductimetric quantification of nitrate (NO₃) provides a highly accurate measure of dissolved N content. With relatively inexpensive equipment and reagents, a single technician can digest and assay over a hundred samples a day. This rapid, simple, and accurate assay may make it possible to routinely monitor DON where it had previously been impractical. This in turn could substantially enhance understanding about the form and quantity of N involved in nutrient fluxes.     

Inorganic nitrogen supply and symbiotic dinitro‐gen fixation in alfalfa

It may be desirable to minimize dinitrogen (N₂) fixation in alfalfa (Medicago saliva L.) when a source of inorganic nitrogen (N), such as manure, is readily available. Our objectives were to determine the N₂ fixation response of eight alfalfa germplasms to inorganic N and to characterize plant‐to‐plant variation for this trait. Seed was sown in vermiculite and irrigated with nutrient solution in growth chambers. Herbage was removed at 71 d and treatments of 1, 3, 5, or 10 mM N were applied as ¹⁵N‐depleted ammonium nitrate (NH₄NO₃). After 34 d of regrowth, herbage was removed and analyzed for dry mass, total N concentration, and N isotope ratio. Increased availability of inorganic N resulted in a linear increase in herbage weight, height, shoot number, and N concentration, and consistently decreased N₂ fixation for all germplasms. Estimated N₂ fixation was greater than zero at the highest rate of inorganic N, which we speculate was due, in part, to remobilized root and crown N, because nodules appeared to be nonfunctional. Across all treatments, N₂ fixation correlated best with herbage N concentration, but there was no relationship between these variables within a given N treatment concentration. Significant variation in reliance on N₂ fixation in the presence of inorganic N existed in all eight germplasms.     

Influence of split‐applied nitrogen on grain yield and protein content in ten grain sorghum culti‐vars 1

More information on the response of newly developed or introduced grain sorghum cultivare to split‐applied nitrogen (N) in semi‐arid rainfed agriculture is needed. Therefore, the influence of four split‐applied N schedules (100/0, 66/34, 50/50, and 34/66) on six American (SC 283, SC 274, SC 669, B 66181, SC 33, and RTam 428), and four West African (CSm 63, 1S 6704c, 1S 7173c, and 1S 7419c) grain sorghum cultivars was evaluated. The split‐applied N significantly increased grain yield and percent protein in grain sorghum over a one‐time application of N. The increase in yield and protein content varied among varieties and schedules of N application. Varieties SC 574, RTam 428, and Csm 63 at split‐applied schedules of 66/34, 50/50, and 34/66, respectively, gave the highest yield over one‐time application of N. Similar differences in percent protein in grain among cultivars due to split‐applied N were observed.     

Assessment of long-term barley–legume rotations in a typical Mediterranean agro-ecosystem: grain and straw yields

Traditional Mediterranean rainfed cereal/fallow systems are being replaced by cereal monoculture due to land-use pressure. Food or forage legumes in rotation with cereals are an alternative sustainable cropping system. Complex cropping systems can only be assessed by long-term trials. This 11-year rainfed barley-based rotation trial in northern Syria assessed rotation effects on yields of barley and legumes, with particular emphasis on the management of vetch. The mean order of barley grain yields from the rotations was: vetch for hay, vetch for grazing > fallow = medic = vetch for seed > lentil, and continuous barley. Straw yields followed a similar pattern. Nitrogen (60 kg ha^?1) increased grain (39%) and straw (65%) yields. The N fertilization of barley had no carryover effect on the alternative legume crops. Although there were no significant differences in seed or straw yield between lentil and vetch, seasonal rainfall influenced overall yields. Total biomass yields were in the order of vetch, medic and lentil. There is a compelling case for annual vetch paired with barley in rotations for the Mediterranean region. Thus, barley/vetch rotations can potentially enhance barley yields and improve soil quality, and provide valuable fodder for small ruminants as well in the region's agricultural systems.     

Excessive nitrogen application decreases grain yield and increases nitrogen loss in a wheat–soil system

Abstract

Excessive use of nitrogen (N) fertilizers in wheat fields has led to elevated NO₃-N concentrations in groundwater and reduced N use efficiency. Three-year field and ¹⁵N tracing experiments were conducted to investigate the effects of N application rates on N uptake from basal and topdressing ¹⁵N, N use efficiency, and grain yield in winter wheat plants; and determine the dynamics of N derived from both basal and topdressing ¹⁵N in soil in high-yielding fields. The results showed that 69.5–84.5% of N accumulated in wheat plants derived from soil, while 6.0–12.5%and 9.2–18.1% derived from basal ¹⁵N and top ¹⁵N fertilizer, respectively. The basal N fertilizer recovery averaged 33.9% in plants, residual averaged 59.2% in 0–200 cm depth soil; the topdressing N fertilizer recovery averaged 50.5% in plants, residual averaged 48.2% in 0–200 cm soil. More top ¹⁵N was accumulated in plants and more remained in 0–100 cm soil rather than in 100–200 cm soil at maturity, compared with the basal ¹⁵N. However, during the period from pre-sowing to pre-wintering, the soil nitrate moved down to deeper layers, and most accumulated in the layers below 140 cm. With an increase of N fertilizer rate, the proportion of the N derived from soil in plants decreased, but that derived from basal and topdressing fertilizer increased; the proportion of basal and top ¹⁵N recovery in plants decreased, and that of residual in soil increased. A moderate application rate of 96–168 kg N ha^?1 led to increases in nitrate content in 0–60 cm soil layer, N uptake amount, grain yield and apparent recovery fraction of applied fertilizer N in wheat. Applying above 240 kg N ha^?1 promoted the downward movement of basal and top ¹⁵N and soil nitrate, but had no significant effect on N uptake amount; the excessive N application also obviously decreased the grain yield, N uptake efficiency, apparent recovery fraction of applied fertilizer N, physiological efficiency and internal N use efficiency. It is suggested that the appropriate application rate of nitrogen on a high-yielding wheat field was 96–168 kg N ha^?1.     

Relationships between four methods of organic carbon determination in leaves of nitrogen‐fixing trees and lignite‐based organic fertilizers

Abstract

Organic carbon (OC) in leaves of seven nitrogen (N₂)‐fixing trees and fifteen lignite‐based fertilizers was measured by loss‐on‐ignition (LOI at 500°C), wet oxidation by the Walkley‐Black method (CWB), Tinsley Dichromate Method (CTS), and dry combustion method using a LECO SC444 Carbon/ Sulphur Resistance Furnace Analyzer (CTO). There were significant differences in the capabilities of the methods in measuring OC from the organic materials with the quantity measured in the following order: LOI > CTO > CTS > CWB. A highly significant difference between LOI and CTO values suggested that components other than organic carbon (C) were removed by LOI since CTO gives total C value. The result also showed that N content in the organic materials was highly correlated with OC measured by individual methods. The LOI, CWB, and CTS were significantly correlated with CTO. The regression equations which were specific for either plant leaves or lignite‐based fertilizers indicated that any of the methods could be used to predict total C in the organic materials with a high degree of precision. In addition to the regression approach, an estimated correction factor of 1.4550 would be more appropriate to predict CTO from CWB for plant leaves than the 1.30 factor usually used for estimating oxidizable C in soils when CWB method is used. Also, a factor of 0.36180 could be used to estimate total C from LOI method for lignite fertilizers instead of merely regarding the difference in weight loss as the total organic matter.     

Stem‐infused nitrogen‐15 enrichment for evaluation of nitrogen use in maize

Abstract

Nitrogen use efficiency (NUE) of N fertilizer can be accurately estimated by tracing the fate of soil applied ¹⁵N‐labeling. However, the quantity of N remobilization from non‐kernel components into kernels in maize (Zea mays L.) plants is difficult to determine. A field experiment involving stem infusion with four levels of enriched ¹⁵N solution plus non‐infusion or infusion with water was conducted at Ottawa (45°22'N, 75°43'W), Canada to determine the effect of ¹⁵N atom % enrichment (a.e.) on physiological processes associated with NUE. At anthesis, 30 mL of 35.7 mmol N solution as ¹⁵NH₄ ¹⁵NO₃ at 5.0 (N05), 33.0 (N33), 66.0 (N66) and 99.2 (N99) ¹⁵N% a.e. was infused into the internode below the primary cob. The control plants were infused with distilled water. Photosynthesis was measured at 2, 4, 6, 24 h and 1 wk after infusion. Plants were sampled and separated into components at 4 d after anthesis (D4A) and at physiological maturity (PM). Dry weight, total N concentration, NH₄‐ and NO₃‐N, and ¹⁵N% a.e. of each component were determined. At D4A, the N33 and N66 treatments resulted in component ¹⁵N enrichment similar to that of N99 treatment. At PM, however, only N66 treatment produced results similar to that of N99. None of the infused ¹⁵N treatments interfered with ear‐leaf photosynthesis or component NH₄‐ and NO₃‐N concentrations. Infused ¹⁵N was easily moved out of the internode where it was infused, into most components, with the majority in the dominant sinks (cob, husk, and kernels). Nitrogen remobilization in both N66 and N99 treatments accounted for 62% of kernel N. These findings indicate that stem infusion is an appropriate approach to study N remobilization. Based on the concentrations investigated in this study, 66% or higher ¹⁵N% a.e. is required for accurate labeling when soil available N is high.     

Early interspecific dynamics,dry matter production and nitrogen use in Kernza (Thinopyrum intermedium) – alfalfa (Medicago sativa L.) mixed intercropping

ABSTRACT

The global interest in growing perennial grain crops such as intermediate wheatgrass (Thinopyrum intermedium) (Kernza) for production of food and feed is increasing. Intercropping Kernza with legumes may be a sustainable way of supplying nitrogen to soil and associated intercrop. We determined the competitive interactions between intercropped Kernza (K) and alfalfa (Medicago sativa L.) (A) under three inorganic nitrogen (N) rates N0, N1, N2 (0, 200, 400 kg ha^?1) and five species relative frequencies (SRF) (100%K:0%A, 75%K:25%A, 50%K:50%A, 25%K:75%A and 0% K:100%A) in mixed intercrops (MI) in a greenhouse pot experiment. After 11 weeks of growth. Kernza dry matter yield (DM) and N accumulated (NACC) were low, but alfalfa DM and NACC high at 0 kg N ha^?1. 200 and 400 kg N ha^?1 fertiliser application increased the competitive ability (CA) of Kernza and reduced the CA of alfalfa. SRF had large impacts on alfalfa DM, NACC and NFIX only at 0 kg N ha^?1 fertiliser, and insignificant impacts on Kernza at all N fertiliser levels, indicating that adjustment of SRF may not be an effective way to modulate the interspecific competition of Kernza. Further research on the other factors that influence the interspecific competition are warranted.     

Changes in nitrogen and phosphorus concentrations of silicon‐fertilized rice grown on organic soil 1

Rice grown on the organic soils of the Everglades is routinely fertilized with silicon (Si). The objective of this research was to investigate changes in nitrogen (N) and phosphorus (P) concentration in various plant parts in response to Si fertilization. Two cultivars were grown in lysimeters filled with low‐Si soil. Half the lysimeters were fertilized with calcium silicate to provide 2Mg Si ha^‐1 and the other lysimeters remained unfertilized as a control. Nitrogen concentration decreased in all plant parts with Si fertilization. Phosphorus concentration increased with Si. Maturity was earlier in the Si fertilized rice.     

Nitrogen deficiency induced a decrease in grain yield related to photosynthetic characteristics,carbon–nitrogen balance and nitrogen use efficiency in proso millet (Panicum miliaceum L.)

ABSTRACT

Field experiments involving proso millet (Panicum miliaceum L.) cultivar under four nitrogen (N) levels (N0, N60, N105 and N150) were conducted in 2015 and 2016 to explore the decrease in grain yield under N deficiency related to the changes in leaf photosynthetic characteristics, carbon (C)–N balance and N use efficiency. Results showed that N deficiency decreased the net photosynthesis rate, stomatal conductance, transpiration rate and chlorophyll content and increased the intercellular CO₂ concentration of proso millet flag leaves from flowering to maturity. N deficiency negatively regulated the C–N balance and increased the C/N ratio by reducing the total N, soluble protein and soluble sugar contents, resulting in high starch content. N uptake and utilisation were significantly reduced because of less available N. Significantly positive correlations were observed between the grain yield and photosynthetic characteristics or N use efficiency, whereas a negative correlation was found between the grain yield and the C/N ratio. The yields generated by N0, N60 and N105 were lower than that of N150 in both years. The N fertiliser regression formulae developed in the study would provide useful information about the N fertiliser rate of proso millet.     

Sap test to determine nitrate‐nitrogen concentrations in aboveground biomass of winter cover crops

Abstract

In the San Luis Valley of south central Colorado, winter cover crops (WCC) are used to reduce soil erosion and scavenge residual soil‐N. Some San Luis Valley farmers are beginning to use WCC as a source of over‐winter or early‐spring grazing. Common WCC used by farmers, wheat (Triticum aestivum L.) and rye (Secale cereale L.) are reported to accumulate high levels of nitrate nitrogen (NO₃ ^‐‐N) in aboveground biomass that can be toxic to animals. Evaluation and calibration of a quick Cardy Meter² Sap Test (CMST) for determination of NO₃ ^‐‐N status in the field will facilitate the management of these WCC. Field and growth chamber studies were conducted to correlate the CMST with laboratory procedures and with plant and soil parameters. In field and growth chamber studies, the CMST was correlated with standard dry tissue NC₃ ^‐‐N laboratory analysis (P<.001) and with soil inorganic N content (P<.05). These field and growth chamber studies show that the CMST can be a tool in helping farmers identify fields where WCC aboveground biomass is accumulating potentially toxic levels of NO₃ ^‐‐N. Additionally, plant parameters such as nitrogen uptake, biomass, and grain yield of WCC grown under growth chamber conditions were correlated with the CMST readings conducted at the growth stage, Feekes five (P<.05). The growth chamber results suggest that if WCC are grown for grain production, the CMST can help identify the needs for additional nitrogen (N) fertilizer application at Feekes five.     

Improvement of the nitrogen uptake induced by titanium (iv) leaf supply in nitrogen‐stressed pepper seedlings

The beneficial effect of titanium (Ti) on plant metabolism can result in more profitable use of fertilizer applied to a crop. A crop chamber experiment with paprika pepper (Capsicum annuum L., cv. Bunejo) seedlings under differential nitrogen (N) concentration levels in a nutrient solution (100% N, 75% N, 50% N, and 25% N) was performed. A third of the seedlings growing under each N support level remained Ti‐untreated and were used as the reference. Another third of the seedling received one and two 0.042 mM Ti(TV) ascorbate, pH 6.0, leaf spray treatments, respectively. The biomass production of the Ti‐untreated plants was only affected by the N supply of 50% or less. The Ti(IV) leaf spray treatments produced a biomass production greater than that of the corresponding reference plants, and both the 100% N+Ti and 75% N+Ti treatments had the highest biomass production. Seedlings receiving 50% N+Ti had a level of biomass production similar to that for the 100% N without Ti reference plants. In the same way, the 25% N+Ti treatment resulted in a plant fresh weight greater than that for the Ti‐untreated reference plants, although their biomass yields were not significantly lower than that for the corresponding 100% N and 75% N Ti‐untreated reference plants. Only the 50% N and 25% N Ti‐untreated plants had definite total‐N and nitrate‐nitrogen (NO₃‐N) unbalances as compared to the other N rate‐Ti treatments.