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Abstract

Worldwide, nitrogen (N) deficiency is the main yield limiting factor owing to its losses via leaching and volatilization. Urease inhibitors slow down urea hydrolysis in soil by inhibiting urease enzyme activities whereas gibberellic acid is growth regulator. That is why, we evaluated the role of urease inhibitor [N-(n-butyl)thiophosphorictriamide (NBPT)] and gibberellic acid (GA3) in improving nitrogen uptake and yield of maize under different N levels (120 and 150 kg ha−1) along with control. Both N levels alone and in combination with GA3 and NBPT significantly increased yield and yield components of maize over control. In addition, 150 kg N ha−1 + NBPT + GA3 produced highest biological, grain, and stover yields, 1000 grain weight, plant height, and N uptake exhibiting 33.15%, 56.46%, 27.56%, 19.56%, 23.24%, and 78% increase over 150 kg N ha−1, respectively. The sole use of gibberellic acid or NBPT with each level of N also improved the yield and yield components of maize compared to sole N application and control. Furthermore, application of 120 kg N ha−1 along with NBPT and GA3 performed at par to 150 kg N ha−1 + NBPT + GA3 but it was superior than sole applied 150 kg N ha−1 for all the studied traits. These results imply that application of GA3 and/or NBPT can reduce dependence on urea and improve the yield and N uptake in maize by slowing urea hydrolysis in calcareous soils and shall be practiced.

Introduction

Maize (Zea mays L.) belongs to family Poaceae and is one of the most important cultivated crop in tropical and subtropical region of the world (Nabizadeh et al. 2012; Khan et al. 2014a, b). It is the 3rd largest grain crop in Pakistan following wheat and rice (Harris et al. 2007). Maize is an exhaustive crop needs an adequate amount of essential nutrients for its abundant production, in order to fulfill the demand of the rapid increasing population of the world. Nitrogen (N) is an essential nutrient, is a basic constituent of plant growth, and improves crop production and other nutrients uptake (Zaman et al. 2008a, b; Nasim et al. 2018). Nitrogen is a mobile nutrient, it moves and is lost easily from the soil (Junejo et al. 2011) and is usually deficient in calcarious soils (Adnan et al. 2018a; Snyder et al. 2007; Shah et al. 2012). Worldwide increase in crop yield is directly proportional to synthetic fertilizer application, though the higher N fertilizer has drastically declined nitrogen use efficiency (NUE) (Tilman et al. 2002; Liu et al. 2013; Erisman et al. 2007; Turan 2021a).

Occurrence and Functions of Mucilage

A Model of a Mucilage-Supported Diazotrophic Microbiota

Disassembly of the Complex Mucilage Polysaccharide

Sugar Utilization to Support Nitrogenase Activity

Reduction of Oxygen Levels in the Mucilage Environment

Maintaining Low Nitrogen Levels in the Mucilage Environment

Concluding Remarks

Acknowledgement

References

Role for Nitrogen Fixation in Cereal Crops

Nitrogen-fixing microbial associations with nonlegumes, especially cereals, have been a topic of intense interest for more than a century, since such associations could reduce the requirement for nitrogen fertilizers [1–4]. For instance, sugarcane associates with diazotrophic endophytes that contribute to its nitrogen nutrition in some environments [5–7] and a study based on 15N dilution experiments in Miscanthus × giganteus concluded that this bioenergy feedstock could acquire about 16% of its nitrogen from the air [8]. These examples indicate that some monocots have the potential to associate with diazotrophs and acquire small, but significant, amounts of fixed nitrogen from the atmosphere. It has been shown that the model C4 grass Setaria viridis can obtain most of its fixed N from associative nitrogen fixation following inoculation with diazotrophs [9]. The possibility that cereal crops obtain a significant proportion of total N by associative nitrogen fixation has also been suggested by a 50-year assessment of global nitrogen budgets in maize (Zea mays), rice (Oryza sastiva), and wheat (Triticum aestivum), which concluded that up to 24% of the total nitrogen in these crops was derived from nonlegume symbiotic nitrogen fixation [10]. Interestingly, mucilage on aerial roots of sorghum (Sorghum bicolor) with an inset micrograph of Azospirillum brasilense was highlighted on the cover page of the proceedings of a conference on cereal nitrogen fixation held in India in 1984 [11], suggesting that it was suspected more than 35 years ago that sorghum mucilage harbors a diazotrophic microbiota. However, no report on nitrogen fixation in sorghum mucilage was published in the 1984 proceedings volume or elsewhere.

Occurrence and Functions of Mucilage

A key feature of the Sierra Mixe maize landrace mucilage is the abundance of sugars that potentially serve as a source of energy for the diazotrophs. The monosaccharide composition indicated that the mucilage primarily comprises fucose (41%), galactose (36%), arabinose (14%), xylose (3%), glucuronic acid (3%), and mannose (3%) [12]. This composition is similar to the mucilage reported for maize underground roots [15,16]. Osborne et al. found that underground root mucilage contained fucose (61.0%) and glucose (31.4%), while Chaboud found the mucilage to contain galactose (30.7%), fucose (19.3%), glucose (18.5%), xylose (15.2%), and arabinose (13.4%). Both of these previous studies showed high amounts of fucose, xylose, arabinose, and galactose, which agrees qualitatively with the analysis of the Sierra Mixe aerial root mucilage. This monosaccharide composition is not commonly found in plant cell wall polysaccharides and may play a role in signaling associative diazotrophic bacteria that can degrade the mucilage complex polysaccharide and use the released monosaccharides to support growth and nitrogen fixation.

In common nutrient management in peach orchards in China, a large amount of nitrogen fertilizer is used. However, low nitrogen absorption and utilization rate results in nitrogen loss and greenhouse gas emissions, which is not favorable for cleaner production in peach orchards. In this experiment, nitrogen leaching, ammonia volatilization, greenhouse gas emissions under bag-controlled release fertilizer (BCRF) were evaluated. In addition, the impact of BCRF on soil nutrient status in peach orchards, peach root system growth, nitrogen absorption and utilization rate, fruit quality, and the potential for using BCRF in major peach-producing areas in China to reduce the amount of nitrogen fertilizer application were also investigated. Results showed that BCRF maintained a stable supply of nutrients to soil, decreased nitrogen leaching, ammonia volatilization and greenhouse gas emissions while nitrogen loss was significantly reduced from peach orchard soil. Also, BCRF reduced the combined global warming potential at 20-, 100-, and 500-years. A 5-year study revealed that application of BCRF promoted the formation of a dense root system in peach trees by the development of fine roots and a more concentrated root distribution. This extended the lifespan of the root system and improved fruit quality. 15N tracer experiments showed that BCRF significantly increased the absorption and utilization rate of nitrogen by peach trees. BCRF reduced the amount of nitrogen fertilizers applied by 65e82% compared to common fertilizer application methods without decreasing peach yield, so it has huge potential for reducing the amount of nitrogen fertilizer used as well as fertilizer input costs in peach production. The results showed that BCRF has huge application potential as a new, environmentally friendly, low-cost, and efficient fertilizer for cleaner production in peach orchards.

Introduction

The amount of nitrogen fertilizer consumed in China accounts for 30% of total global consumption. However, the utilization rate of nitrogen fertilizer is only 30e40% (Zhu, 2000). Globally, it is estimated that the amount of nitrogen fertilizer consumed will increase to 13
109 e15
109 t/y in 2050 (Matson et al., 1998). Low fertilizer utilization rate is a common problem when chemical fertilizers were used. Among chemical fertilizers, nitrogen loss is particularly serious. Nitrogen use efficiency (NUE) has decreased during the past two decades, with much of this excess nitrogen fertilizer being lost to the environment (MOA, 2007; National Bureau of Statistics of China, 2013). This not only results in direct economic losses but also environmental pollution in some cases when fertilizer application is improperly applied. This causes surface water eutrophication, nitrate nitrogen levels in groundwater exceeding standards, and increased N2O emissions (Zhu, 2000). Direct application of urea into soil will result in rapid hydrolysis and a large loss of nitrogen due to surface runoff, leaching, and volatilization and low absorption and utilization rate of nitrogen fertilizers, resulting in serious environmental pollution problems (Salvagiotti et al., 2008; Pereira et al., 2017; Wang et al., 2004). In addition, the emission of greenhouse gases, e.g. N2O, is also an important cause of nitrogen loss following fertilizer application (Pereira et al., 2015), which is not favorable for clean production in peach orchards.

Spatially explicit, accurate inventories of greenhouse gas (GHG) emissions are of primary importance when calculating the carbon footprint, identifying sources and sinks, pricing carbon pollution, and creating policy that is effective in reducing emissions. However, there are few reports available on methane and nitrous oxide emissions from each type of livestock and crop in all counties of the province due to a lack of statistical data of sub-categories, such as the different fertilizer quantities used in each crop in the county. Because fertilizer input is the most significant factor for N2O emissions from agricultural soils, how to best distribute the total fertilizer mass to a crop-specific fertilizer rate for each county is a major challenge in agricultural management. In this study, authors developed a crop-specific method correlating the recommended fertilizer rate and planted area of each crop for a reasonable distribution of total fertilizer mass to fertilizer rate. This is based on a balance between the sum of fertilizer used in all crops and the total fertilizer mass used by each municipality. Using this method, our calculations in 69 municipalities in the province of Alberta, Canada showed that the fertilizer rate for each crop was reasonably distributed from the total fertilizer mass of a municipality: less than 170 kg-N ha
1 . The obtained fertilizer rates for each crop in 69 municipalities were used in GHG inventories using IPCC 2006 tier 1 and 2 methods. The total CH4 and N2O emissions from agriculture in all of Alberta in 2011 were 328 Gg CH4 yr
1 and 23.5 Gg N2O yr
1 , respectively. The southeastern municipalities generally emitted more CH4 and N2O than northwestern municipalities. The southern municipality of Lethbridge emitted the largest amount of CH4 and N2O of all municipalities (25.3 Gg CH4 yr
1 (7.70% of total CH4 of entire Alberta) and 1.26 Gg N2O yr
1 (5.40% of total N2O of entire Alberta), respectively). This was due to its largest cattle population (414,627 head) and larger synthetic fertilizer input (32,111 ton-N) and planted area (206,077 ha). The second largest CH4 and N2O emission source was also located at the south. The Taber municipality emitted 15.8 Gg CH4 yr
1 (4.80% of total CH4 of entire Alberta) and 1.14 Gg N2O yr
1 (4.80% of total N2O of entire Alberta), respectively.

Introduction

Since the industrial revolution, human activities have increased greenhouse gas (GHG) concentrations in the atmosphere, resulting in climate change with severe consequences for human life and economic development. It has been determined that the main GHGs include carbon oxide (CO2), methane (CH4), and nitrous oxide (N2O). Their concentrations in the atmosphere are heavily affected by human activities, such as combustion of carbon fuels (coal, oil and natural gas), agricultural production of both livestock and crop farms, land use changes and deforestation. The contribution of each GHG to climate change is expressed by its Global Warming Potential (GWP) according to IPCC (Stocker, 2014), which indicates a gas’ capacity to absorb radiation and its lifetime in the atmosphere based on CO2 capacity (Eilers, 2010). Thus, GWPs of CH4 and N2O are, respectively, 25 and 300 of CO2 equivalents for the first 100 years of their lifetime in the atmosphere, based on GWP as one of CO2. While CO2 emissions can partially be offset by CO2 uptake in plants, CH4 and N2O are not subject to photosynthesis or other direct biological offsets. Therefore, CH4 and N2O emitted from agriculture, such as livestock, managed agricultural soils, rice cultivation, burning of savanna, and returned crop residues are GHG net sources (Eggleston et al., 2006). Agricultural soils are estimated to contribute about 65% of global N2O emissions (Reay et al., 2012). Therefore, it is a challenge to reduce GHG emissions as well as maintaining affordable food prices. In Canada, although the combustion of fossil fuels is a major source of GHG emissions, the agricultural activities also result in a relatively large percentage (8%) of CO2, CH4 and N2O emissions (with an additional 3% agricultural fossil fuel and energy use) of Canada’s total GHG emissions in 2006 (Janzen, 2008; Weldemichael and Assefa, 2016).

In tea (Camellia sinensis) plantation areas, soil acidification mainly results from excessive nitrogen fertilization. However, the proposed theoretical explanations for soil acidification due to nitrogen fertilization are still lacking empirical validation because most studies have used short-term incubation periods or pot experiments. Here, both soil and soil solution samples were taken from a tea plantation field (Ultisol in USDA taxonomy system, or Alisol in WRB taxonomy system) treated using different nitrogen application rates: 0 (N0), 119 (N119), 285 (N285), and 569 (N569) kg N ha−1 yr−1 for 8 years (2006–2013). Soil pH and the concentrations of the relevant cations and anions were also determined. With no nitrogen fertilization (N0), the surface soil pH decreased from 4.16 to 3.32 after 8 years in the tea plantation. Compared with no nitrogen fertilization (N0), high nitrogen fertilization (N569) significantly decreased the soil pH from 3.32 to 3.15 and 3.67 to 3.35 in the soil at depths of 0–40 cm and 40–90 cm, respectively. However, the low (N119) and moderate (N285) nitrogen treatments showed non-significant effects upon soil pH. Our results confirm the previous findings that a high nitrogen application rate can accelerate soil acidification in a tea plantation, and that the subsoil is particularly susceptible to acidification after heavy nitrogen fertilization. Soil acidification also significantly decreased the nutrient base cations Ca2+, Mg2+, and K+ in the soil. Our results suggest that heavy synthetic nitrogen fertilization should be partly replaced with compound or organic fertilizers to mitigate soil acidification and nutrient cation deficiency in tea plantation fields.

Introduction

The tea plant (Camellia sinensis) is an important cash crop cultivated in many tropical and subtropical countries. Unlike many other crops, tea is a perennial leaf-harvested crop that grows best in acidic soil with an optimum pH between 4.0 and 5.5 (Ruan et al., 2007; Fung et al., 2008). Nevertheless, soil acidification can lead to the accumulation of aluminum (Al) and deficiencies in phosphorus (P), potassium (K), and magnesium (Mg) nutrients in tea field soil (Tachibana et al., 1995; Wang et al., 1997; Ruan et al., 2012). Concerning the quality of tea, soil acidification can increase the content of heavy metals (e.g., lead, Pb) and fluorine (F) in the harvested leaves, which may entail a risk to human health (Ruan et al., 2003; Jin et al., 2005; Zhang and Fang, 2007). Generally, N fertilization or deposition is considered the major driver of soil acidification in croplands (Debreczeni and Kismanyoky, 2005; Schroder et al., 2011; Cai et al., 2015), grasslands (Martins et al., 2014; Chen et al., 2015), and forest ecosystems (Hogberg et al., 2006; Zhu et al., 2016). Specifically, it is thought that the accelerated soil acidification from N fertilization is directly caused by the production of protons via the nitrification process after ammonium nitrogen fertilization occurs (Barak et al., 1997; Zhou et al., 2014). The generated hydrogen ions (H+) are buffered by a suite of factors, including carbonate, silicate, exchangeable base cations, and the Al and/or iron (Fe) content, which depend on the soil pH (Bowman et al., 2008). Since base cations enter the soil solution as accompanying ions with the leaching NO3 −, the buffering capacity of soil is consequently decreased under increasingly acidic conditions (Lucas et al., 2011). How much N fertilization contributes to soil acidification remains unclear since the latter could happen naturally in tea plantation settings. Ding and Huang (1991) proposed that this might arise when the accumulated Al in the tea plant residue returns to the soil via litter fall and regular pruning. Recent studies have revealed that the root uptake of NH4 + and Al3+, and the subsequent release of protons, could also cause soil acidification in tea plantations (Ruan et al., 2004; Wan et al., 2012). However, several processes may also weaken the rate of soil acidification in tea plantation soil. The contribution of nitrification to soil acidification could be diminished by reductions in the availability of substrate, as tea plants preferentially assimilate NH4 + (Ruan et al., 2007). Additionally, the soil acidification rate may be reduced by less nitrate leaching, since the nitrification rate is typically inhibited by a low soil pH (Kemmitt et al., 2005).

The carbon defects in nitrogen-doped carbon were controlled by removing the N atoms under different temperatures during the catalyst preparation process. The synthesised catalysts were characterised by multiple techniques, and the catalytic performance was evaluated under experimental conditions of gas hourly space velocity (C2H2) = 36 h−1 at 220 °C. The catalytic performance of the synthesised nitrogen-doped carbon for acetylene hydrochlorination increased with the increment of carbon defect. Carbon defects in the catalysts were proposed to affect the adsorption of C2H2 and HCl and promote their conversion. The regeneration of the nitrogen-doped carbon catalyst was found to be effective by using high-temperature treatment in an NH3 atmosphere.

Introduction

Acetylene hydrochlorination is a very important method for manufacturing vinyl chloride monomer (VCM) in China because China contains rich deposits of coal but lacks oil. However, the industrial catalyst for acetylene hydrochlorination is HgCl2, which is toxic to the human body and the environment [1]. Therefore, the exploitation of environmentally friendly non-mercury catalysts is attracting increasing attention for acetylene hydrochlorination. In the past decades, Au catalysts have been found to be effective for acetylene hydrochlorination. In our previous work, we designed an Au catalyst whose acetylene conversion rate reached 100%. This catalyst could be stably used for 6513 h under industrial application conditions [2,3]. Wei et al. [4] found that a Au catalyst with thiocyanate ligands could operate for over 3000 h in a 4 t per annum scale pilot experiment. Hutchings et al. [5] reported very exciting results for the development of non-mercury acetylene hydrochlorination catalysts. By using thio ligands as soft donor atoms, active Au+ and Au° were present consistent with the formation and deposition of Au catalyst, and the synthesised catalyst could last over 3000 kg VCM/kg catalyst, which is a very low Au loading. These investigations greatly accelerated the commercialisation of non-mercury catalysts for acetylene hydrochlorination. However, given the high cost and scarcity of Au, low-cost catalysts are being sought as non-mercury replacement catalysts for acetylene hydrochlorination. In our previous work, we synthesised C3N4 for acetylene hydrochlorination, and we found that the acetylene conversion rate of this catalyst can reach 75% of the HgCl2 catalyst efficiency. According to density functional theory (DFT) calculations, carbon atoms were the adsorption sites for acetylene, and nitrogen atoms were the adsorption sites for hydrogen chloride [6]. The reaction activation energy was 77.94 kcal/mol, which is much higher than AuCl3 (11.9 kcal/mol) [7]. Thereafter, many groups have synthesised catalysts with nitrogendoped carbons that display excellent catalytic performance. Wei et al [8]. reported nitrogen-doped carbon nanotubes that could greatly enhance the adsorption of acetylene. This catalyst showed excellent catalytic properties with turn over frequency (TOF) of up to 2.3 × 10−3 /s. Pan et al. [9] found that the catalyst activity increased with increasing N content, and only carbon atoms linked to pyrrolic nitrogen could adsorb acetylene. Thus, they found that the type of nitrogen played a major role in this reaction. The catalyst performance stabilised at above 80% under 30/h (C2H2) and 200 °C during 150 h. In our previous work, we considered the effect of the nitrogen species in the nitrogen-doped catalyst for acetylene hydrochlorination and found that the effectiveness of the nitrogen species for acetylene hydrochlorination followed this order: pyrrolic N > graphitic N > pyridinic N [10]. On the basis of that sequence, we then designed and synthesised boron and nitrogen dual-doped graphene (B, N-G) materials. The acetylene conversion on that catalyst could reach to 95%, which was very close to the performance of Au and Hg catalysts [11].

Soil is the primary support for soil-grown crops. It is an important medium for plant root extension and the main nutrient source for crop growing. The main soil nutrients include TN, OM, available potassium, and available phosphorus (Chacón Iznaga et al., 2014; Sinfield et al., 2010). Among those soil nutrients, soil nitrogen (TN and available nitrogen) plays the most important role in promoting the growth of leaf, root, and stem and is a decisive factor to the crop yield (Bansod and Thakre, 2014). Excessive nitrogenous fertilization however will cause environmental pollution and crop distortion of growth and quality. The amount of nitrogen fertilizer applied therefore needs to be precisely controlled to ensure the crop yield and environmental protection. The fundament of precision fertilizing is effectively acquiring the soil information in the field. Rapid and precise acquisition of soil nitrogenous information in farmlands hence becomes increasingly important. The conventional method of detecting soil nitrogen content usually takes several days and consumes toxic chemicals. The conventional method also has several disadvantages, such as high requirements for detection personnel, expensive testing equipment, low efficiency, and environmental pollution (Debaene et al., 2014; Florinsky et al., 2002; Kuang and Mouazen, 2013; Moore et al., 1993; Nocita et al., 2014). By contrast, spectral analysis techniques are based on the internal relations between radiation energy and the composition and structure of matters. According to the characteristic spectra of matter, the target concentration or properties can be determined rapidly without chemicals (Igne et al., 2010; Vohland et al., 2011). For soil, the spectral information related to most of the organic radical groups containing hydrogen was in the NIR region (Li, 2006). NIR spectroscopy is a rapid, non-destructive, and non-pollutant testing method that plays an growing important role in soil nutrition measurement and exhibits extraordinary development potential in applications of soil TN content detection (Chang et al., 2001; Lucà et al., 2017; Morellos et al., 2016). In the detection of soil TN content with NIR spectroscopy, the spectra of soil samples are first measured, and the NIR spectral data are then used as the input variables to establish the prediction models. Modern spectrometers possess high spectral resolution, and spectral data measurement generally involves hundreds or thousands of wavelength variables. Three kinds of information variables are involved in measurement of such superlarge-scale data. One is the effective informative variable, which can improve the model predictive ability because it reflects the characteristics of the target substance in the NIR region. The second is redundant or interfering variable, which is related with other targets. The last one is uninformative variable, which is irrelevant to the target material and usually caused by the measurement environment, such as noise. If the prediction model was established by the entire-spectrum information, then the latter two kinds of variables would increase the computation complexity and reduce the target prediction accuracy of the model.

The agricultural sector produces food, fuel, and fiber but is also an important source of greenhouse gas (GHG) emissions. Agriculture contributes around 9% of total United States GHG emissions, with carbon dioxide (CO2) making up the majority (81%), followed by methane (CH4) (11%) and nitrous oxide (N2O) (6%) (EPA, 2016). The global warming potential (GWP) of N2O and CH4 is 298 and 25 times greater than that of CO2, respectively. Global warming potential is a measure of the amount of energy one kilogram of a certain GHG will absorb over a given time period, usually 100 years, relative to CO2 (EPA, 2016). Agricultural soil management which includes synthetic fertilizer application and use, tillage practices, and crop rotation systems accounts for around 80% of total N2O emissions in the U.S. annually (EPA, 2016) (Venterea et al., 2011). Nitrous oxide emissions are directly affected by N application rate as well as fertilizer source and crop type (Eichner, 1990; FAO, 2001). Likewise, fertilizer application technique and timing, use of other chemicals, irrigation, and residual N and C from previous crops and fertilizer all affect N2O emissions (Eichner, 1990). Application of N fertilizer stimulates N2O production by providing a substrate for microbial N conversion through nitrification and denitrification (Venterea et al., 2005; Norton, 2008). Nitrification occurs when ammonium is either added to the soil in the form of fertilizers, as N fixation by legumes, or as mineralized soil organic matter (SOM) (Paustian et al., 2016). During this microbial process, ammonium is converted to nitrite and eventually to nitrate, yet small quantities can be lost as N2O (Snyder et al., 2009). Likewise, in conditions olow soil oxygen, denitrifiers use nitrate as a terminal electron acceptor and N2O is an intermediate step in complete denitrification to N2 gas (Aulakh et al., 1992; Robertson et al., 2007; Paustian et al., 2016). Since spring fertilizer application in the United States Corn Belt (Illinois, Iowa, Indiana, Ohio southern and western Minnesota, and eastern Nebraska) occurs when saturating rains are common, the soil may easily become water-logged, promoting large denitrification events wherein a large proportion of annual N2O flux can occur over short time scales (Venterea et al., 2012). Tillage studies often have mixed results with no-till (NT) or reduced till having less, more, or no effect on N2O emissions compared to conventional tillage systems (T) (Venterea et al., 2005; Rochette et al., 2008; Snyder et al., 2009). Snyder et al. (2009) compared various cropping rotation studies and found that continuous corn (Zea mays L.)- (CCC) had higher yields compared to a corn-soybean [Glycine max (L.) Merr.]-wheat (Triticum aestivum L.) (CSW) rotation. While CCC resulted in a two to three times higher N2O emissions, it produced four to five times the food yield in caloric value compared to the CSW rotation. Parkin and Kaspar (2006) observed that a corn-soybean (CS) rotation did not differ in N2O emissions between T and NT, but corn in the rotation emitted more N2O than did soybeans. In a meta-analysis by Pittelkow et al. (2015) studying the long-term effects of no-till on yield in several agroecosystems, the authors found that after 5+ years of notill, soybean and wheat yields matched that of conventional tillage; however, corn yields did not improve over time compared to conventional tillage. Relatively few studies have compared side-by-side crop rotation effects as influenced by tillage, and since both of these practices tend to influence soil properties more over time, long-term assessments are needed which allow for soils to stabilize.