Tillage Timing Research Articles

Effect of tillage on macronutrients in soil and wheat of a long-term dryland wheat-pea rotation

Tillage is known to significantly affect crop residue decomposition and soil nutrient dynamics, but the impacts of tillage on soil and plant macronutrients concentration with time have not been reported. This study was conducted (i) to assess the influence of tillage timing and intensity on soil and wheat (Triticum aestivum L.) macronutrient concentration of a winter wheat-dry pea (Pisum sativum L.) rotation (WW-P) under a dryland cropping system, and (ii) to compare macronutrients in the tillage treatments with a nearby long-term grass pasture (GP). The tillage treatments were fall tillage (FT), spring tillage (ST), no-tillage (NT) and disk/chisel tillage (DT/CT). Soil samples from 1995, 2005, and 2015 were analyzed to determine the concentration of soil organic carbon (SOC), total N and S, Mehlich III extractable P, K, Ca, and Mg, and soil pH. The impact of tillage on soil macronutrient concentration was evident after 52 years of WW-P. As a result, greater concentration of SOC, total S, and extractable P, and K were observed under NT than under FT or ST. The WW-P plots lost 28, 46, and 67% of SOC, Mg, and S, respectively, in the top 10 cm of soil compared with the GP plots, whereas the NT plots were the only plots in WW-P to maintain a P concentration (99 mg P kg−1) comparable with GP plots (102 mg P kg−1) at the same depth. The results indicated that NT could be beneficial to recharge the soil nutrient pool over time compared to FT or ST.

Influence of Tillage Depth and Plough Speed on Performance of Primary Tillage Tools

In India near about 60% population is engaged in agriculture. Soil loosening is a primary method of cultivation before seeding. There are number of tillage tools used for primary cultivation i.e. cultivators, rotary tillers, moldboard plough and chisel plough, rotavators etc. During soil cultivation wear occurs due to interaction of tillage implement and soil particles, which in turn decreases tillage quality and increase draft forces and fuel consumption of tractor. Tool wear reduces farmer’s efficiency, costing millions of dollars per year to Nation’s economy. Knowledge of tillage depth and ploughing speed save the tillage time and improves tractor efficiency. In this study it is attempted to relate the influence of tillage depth and tractor speed on primary tillage tools.

Giant Ragweed Emergence Pattern Influenced by Spring Tillage Timing in Minnesota

Core Ideas Delayed pre‐plant tillage effectively controls herbicide‐resistant giant ragweed. Spring tillage did not affect total giant ragweed emergence. Early tillage treatments suppressed giant ragweed emergence the week following tillage

Transplanting into non-puddled soils with a small-scale mechanical transplanter reduced fuel, labour and irrigation water requirements for rice (Oryza sativa L.) establishment and increased yield

Mechanizing the transplanting of rice can decrease labour requirement and costs for crop establishment. The cost of crop establishment can also be reduced by changing from conventional tillage with puddling to reduced tillage in non-puddled soil. However, mechanized rice transplanters for suitable for the small-scale fields of Asia have not been evaluated on non-puddled soils. This study was conducted to evaluate the performance of a 4-row walking-type mechanical rice transplanter under different tillage options for rice establishment. Field experiments were conducted on a clay loam soil in Gazipur and on a loam soil in Kushtia during the irrigated dry (Boro) season in 2012–13 and the non-irrigated wet (Aman) season in 2013. Three non-puddled soil treatments (shallow beds, strip tillage on the flat, zero tillage on the flat) were compared with conventional puddled tillage (‘puddling’). The non-puddled plots were flooded 18 h before transplanting to soften the soil.Strip tillage reduced tillage time and fuel consumption for tillage by 50–70% relative to puddling. Strip and zero tillage also reduced the irrigation water input for transplanting by 22 and 28%, respectively. The transplanter had a significantly higher rate of area coverage in strip and zero tilled soil (0.131–0.134 ha/h) than in puddled soil and beds (0.115–0.121 ha/h). Non-puddled strip and zero tillage also reduced fuel consumption for mechanical transplanting by 11–18 % compared to puddling. The proportion of missing hills was lower in strip tilled soil than in puddled soil, and there were fewer missing hills due to less floating and burial of plants. Transplanter slippage significantly reduced the plant to plant spacing during transplanting in puddled soil compared to the spacing in non-puddled soil.All non-puddled tillage treatments gave similar or significantly higher yield of rice compared to puddling. On the clay loam soil, strip tillage and zero tillage gave significantly higher yields (5.4–5.6 t/ha) than bed tillage and puddling (5.1–5.2 t/ha). On the loam, yields with strip tillage (5.1 t/ha) and bed tillage (4.9 t/ha) were similar, and yield with strip tillage was significantly higher than that of zero tillage and puddling (4.7–4.8 t/ha). Operating the mechanical rice transplanter in non-puddled soil reduced labour and fuel costs and irrigation water input for rice establishment. Crop production was profitable with mechanized transplanting into all tillage treatments at both sites in both seasons, with gross margin ranging from US$273 to US$582/ha, and BCR from 1.3 to 1.7. Strip tillage and zero tillage were more profitable than puddling at Gazipur, while strip tillage was also the most profitable treatment at Kushtia. Mechanized transplanting into non-puddled soil is thus a promising option for smallholder wetland rice farmers in Asia.

Consolidation and surface sealing of nine harrowed Swedish soils

The structure of agricultural topsoils varies considerably throughout the year due to interactions between climatic and biological factors and agricultural management practices. Tillage generally decreases soil density and increases macroporosity, but the resulting arrangement of clods and aggregates is unstable and the soil eventually reverts back to its denser pre-tillage condition. Accounting for post-tillage changes in soil structure and related hydraulic properties could greatly improve model predictions of hydrological and transport processes. Model testing, development and parameterization is, however, currently hampered by a lack of direct measurements of the changes occurring in the structural pore system. We subjected repacked samples of soil collected from the harrowed layer of nine different fine- and medium-textured Swedish mineral soils to subsequent wetting and drying cycles in the laboratory. Initial wetting and equilibration at −30 cm pressure potential was followed by three cycles of simulated rainfall (5 mm h−1 for 4 h) and equilibration. X-ray tomography was used to quantify changes in surface and total porosity, pore size distribution (PSD) and connectivity of structural pores.Total porosity decreased (by 2–24%) in all soils except for two clay soils where in one case the porosity increased slightly (3%) and remained unchanged in the other. In six of the soils, the PSD shifted significantly towards smaller pore sizes, and in four of these soils the connectivity of the pore network decreased. Soil surface porosity decreased most markedly in two silt loam soils (by 73% and 75%). For the nine soils changes were strongly correlated with silt content. Only weak correlations were found between the changes in total porosity and soil texture and organic carbon content. Changes in the PSD appeared to be mainly controlled by the initial structure of the sample created at the time of tillage and sample preparation.

The C-biogeochemistry of a Midwestern USA agricultural impoundment in context: Lake Decatur in the intensively managed landscape critical zone observatory

The damming of rivers has created hotspots for organic carbon sequestration and methane production on a global scale as the reservoirs intercept fluvial suspended and dissolved loads. To better understand how the C-biogeochemistry of a reservoir responds to watershed processes and evolves over time, Lake Decatur, located in the Intensively Managed Landscape Critical Zone Observatory (IML-CZO) was studied. Solid phase analyses (% organic C, C/N, δ13C, δ15N) of soils and sediments sampled from stream bank exposures, river suspensions, and the lake bottom were conducted to characterize organic C (OC) sources throughout the sedimentary system. Agriculturally-driven soil erosion rapidly altered lake bathymetry causing an evolution of sedimentary and OC deposition patterns, which in turn shaped where and when methane production occurred. A positive correlation between OC accumulation rate and porewater dissolved inorganic C (DIC) δ13C profiles indicates that methane generation is strongly influenced by OC burial rate. The sources of the lake bed particulate organic C (POC) have also evolved over time. Drowned vegetation and/or shoreline inputs were dominant initially in areas adjacent to the original river channel but were rapidly overwhelmed by the deposition of sediments derived from eroded agricultural soils. Eutrophication of the lake followed with the onset of heavy fertilizer application post-1960. This succession of sources is expected to be commonplace for reservoirs greater than ~ 50–60 years old in agricultural settings because of the relative timing of tillage and fertilizer practices. The 13C/12C ratios of methane from Lake Decatur were more depleted in 13C than what is commonly expected for freshwater sedimentary environments. The 13C-depletion suggests that CO2-reduction is the dominant methanogenic pathway rather than the anticipated acetate dissimilation process. The isotopic observations reveal that commonly held assumptions about methane production and its C-isotopic signature in freshwater systems are over-simplified and not strictly applicable to this system.

Timing and depth of post-harvest soil disturbance can reduce seedbank and volunteers of oilseed rape

Appropriate timing of post-harvest tillage to oilseed rape (OSR, Brassica napus L.) is crucial for the creation of a soil seed bank and unwanted OSR volunteers. Existing recommendations, however, can contrast with needs for early post-harvest tillage e.g. for pest control. To specify and to systematically further improve preventive volunteer management through post-harvest tillage of imidazolinone-tolerant oilseed rape (Clearfield®; CL OSR), field experiments were set up at two locations in two separate trial periods at each location (2013–2014 and 2014–2015) in south-west Germany. After OSR harvest, and average harvest losses of 1500 m−2 seeds, or artificially broadcasting of 20000 OSR seeds m−2, stubble tillage was performed at weekly intervals (immediate (0), 1, 2, 3, and 4 weeks) at each of three depths (1–2, 6–8, and 15–17cm). To depict a worst case scenario in which herbicides were ineffective, no herbicides were applied. There were significantly smaller soil seed banks found in spring the longer the period lasted between seed rain and stubble tillage; 265 vs 145 seeds m−2 referred to 0 week vs. 4 weeks on average. Depth of stubble tillage had no significant effects on the seed number in the soil. In the first spring after seed loss, 0–2.6 CL OSR volunteers m−2 were found in the winter wheat, and the number decreased with delayed timing depth of stubble tillage. These volunteers mainly emerged in the treatment of shallow stubble tillage (1–2cm), with 0.7-0.9 flowering volunteer m−2, while volunteers averaged less than 0.04 plants m−2 in the treatment “15–17cm”. OSR volunteers in winter wheat got ripened only in one out of the four fields, and produced 1.0 seed m−2 on average. The delay between harvest and stubble tillage can be limited to approximately three weeks if stubble tillage is performed at a depth of about 6–8cm; further delay did not bring additional advantage. We recommend to retain the stubble for three weeks as further delay does not bring additional advantage, and then to apply stubble tillage deeper than 6cm. Very superficial or shallow stubble tillage should be avoided. This procedure seems appropriate for avoiding oilseed rape volunteers without use of herbicides.

How do weeds differ in their response to the timing of tillage? A study of 61 species across the northeastern United States

AbstractPrevious research has demonstrated that the season in which soil is tilled (spring versus fall) can strongly influence weed community assembly and subsequent species composition and abundance in annual cropping systems. Despite this understanding, it is unknown whether finer‐scale, within‐season variation in the timing of tillage has similar impacts on weed community assembly. We conducted an experiment on four research farms across the northeastern USA to test the effects of tillage timing on weed emergence periodicity. Soil was tilled at 12 different times that were 2 weeks apart from 29 April to 30 September (the entire growing season) and the composition and abundance of the weed seedlings that emerged was measured 6 weeks later. Weed species clustered into three tillage timing groups at the two New York locations and clustered into five tillage timing groups at the New Hampshire and Maine locations. Individual species associated with each window of tillage time varied by location. No single trait or combination of traits were consistently associated with species‐by‐tillage time groupings across locations; however, within each location several traits were associated with particular groups of species, including: (a) seed length, (b) seed weight, (c) cotyledon type, (d) life span, (e) ploidy level and (f) photosynthetic pathway. These results suggest that fine‐scale variation in the timing of tillage can lead to predictable changes in the species composition and trait distribution of weed communities in annually tilled agroecosystems.

水稲の不耕起および簡易耕起栽培法 : 第3報 耕起時期と施肥が表層代かき同時移植水稲の生育・収量に及ぼす影響

水稲の不耕起および簡易耕起栽培法 : 第3報 耕起時期と施肥が表層代かき同時移植水稲の生育・収量に及ぼす影響

Disentangling the Effects of Tillage Timing and Weather on Weed Community Assembly

The effect of tillage timing on weed community assembly was assessed at four locations in the Northeastern United States by tilling the soil every two weeks from April to September and quantifying the emerged weed community six weeks after each tillage event. Variance partitioning analysis was used to test the relative importance of tillage timing and weather on weed community assembly (106 weed species). At a regional scale, site (75.5% of the explained inertia)—and to a lesser extent, timing—of tillage (18.3%), along with weather (18.1%), shaped weed communities. At a local scale, the timing of tillage explained approximately 50% of the weed community variability. The effect of tillage timing, after partitioning out the effect of weather variables, remained significant at all locations. Weather conditions, mainly growing degree days, but also precipitation occurring before tillage, were important factors and could improve our ability to predict the impact of tillage timing on weed community assemblages. Our findings illustrate the role of disturbance timing on weed communities, and can be used to improve the timing of weed control practices and to maximize their efficacy.

Timing of Tillage as a Driver of Weed Communities

Tillage is a foundational management practice in many cropping systems. Although effective at reducing weed populations and preparing a crop seedbed, tillage and cultivation can also dramatically alter weed community composition. We examined the impact of soil tillage timing on weed community structure at four sites across the northeastern United States. Soil was tilled every 2 wk throughout the growing season (late April to late September 2013), and weed seedling density was quantified by species 6 wk after each tillage event. We used a randomized complete block design with four replicates for each tillage-timing treatment; a total of 196 plots were sampled. The timing of tillage was an important factor in shaping weed community composition and structure at all sites. We identified three main periods of tillage timing that resulted in similar communities. Across all sites, total weed density tended to be greatest and weed evenness tended to be lowest when soils were tilled early in the growing season. From the earliest to latest group of timings, total abundance decreased on average from 428±393 to 159±189 plants m−2, and evenness increased from 0.53±0.25 to 0.72±0.20. The effect of tillage timing on weed species richness varied by site. Our results show that tillage timing affects weed community structure, suggesting that farmers can manage weed communities and the potential for weed interference by adjusting the timing of their tillage and cropping practices.

Sustainability status of technology application on rice farming in peatlands (case study at Kanamit Jaya village, Central Kalimantan)

<p>Peatlands become one of the potential resources that could be developed as an area of rice farming to improve national food security. Agricultural cultivation in peatlands, if not managed well, will contribute to environmental destruction and land degradation, which will ultimately affect land productivity. As a first step in preparing the development of rice farming, research on the application of technology has conducted. This research included water management, which consists of: without water management or control (A0), <em>macak-macak</em> water management (A1) and intermittent water management (A2). Moreover, research on pesticide application was also conducted which consist of: without pesticide application or control (P0), Paraquat herbicide application at the time of tillage (P1), Fenobucarb insecticide applications every week (P2), Fenobucarb insecticide applications every two weeks (P3), Difenoconazole fungicide applications every week (P4), Difenoconazole fungicide applications every two week (P5). This study aims to determine the level of sustainability of rice farming in peatlands, and the dominant factors that influence by considering economic, social and environmental through a Multi Dimensional Scaling (MDS) approach. The analysis shows a quite sustainable level, with score for each dimension is 53.13 for the economic dimension, 69.49 for the ecological dimension and 61.79 for the social dimension. The dominant factors to be considered for the sustainability of rice farming in peatlands are changes in the level of decomposition of organic matter, farming purpose and outreach intensity.</p>

Strategic tillage on a Grey Vertosol after fifteen years of no-till management had no short-term impact on soil properties and agronomic productivity

Over half of the arable land in the northern grains region of Australia is managed using no-till (NT), a farming method which has improved crop yields and soil quality while reducing the input and labour costs. However, concerns have arisen among farmers over the control of weeds in continuous NT systems. An occasional targeted tillage operation (termed strategic tillage — ST) has been proposed as a management tool to reduce problem weed populations but may adversely influence soil properties and those of associated microbial communities. To assess the potential impacts of a ST operation on soil properties, a Grey Vertosol with fifteen years of NT in Northern New South Wales, Australia was tilled using either a chisel cultivator or disc chain on March 15th 2013 or on April 5th 2013. We hypothesised that ST using these minimal or low soil inversion implements at either timing would not adversely influence soil properties in the short-term (4–7weeks). The measured soil properties were soil volumetric moisture content (VMC), pH, bulk density (BD), electrical conductivity (EC), available phosphorus (P), soil organic carbon (SOC), microbial biomass carbon (MBC), metabolic activity (MA), genetic structures of bacterial communities and wheat yield (tha−1). We found that ST with either a chisel cultivator or a disc chain has great potential to assist in weed management as it did not statistically influence crop productivity or the physical, chemical and biological properties of the soil, regardless of the tillage timing.

Drivers of nitrogen dynamics in ecologically based agriculture revealed by long-term, high-frequency field measurements.

Nitrogen (N) loss from agriculture impacts ecosystems worldwide. One strategy to mitigate these losses, ecologically based nutrient management (ENM), seeks to recouple carbon (C) and N cycles to reduce environmental losses and supply N to cash crops. However, our capacity to apply ENM is limited by a lack of field-based high-resolution data on N dynamics in actual production contexts. We used data from a five-year study of organic cropping systems to investigate soil inorganic N (SIN) variability and nitrate (NO3-) leaching in ENM. Four production systems initiated in 2007 and 2008 in central Pennsylvania varied in crop rotation, timing and intensity of tillage, inclusion of fallow periods, and N inputs. Extractable SIN was measured fortnightly from March through November throughout the experiment, and NO3- N concentration below the rooting zone was sampled with lysimeters during the first year of the 2008 start. We used recursive partitioning models to assess the importance of management and environmental factors to SIN variability and NO3- leaching and identify interactions between influential variables. Air temperature and tillage were the most important drivers of SIN across systems. The highest SIN concentrations occurred when the average air temperature three weeks prior to measurement was above 21 degrees C. Above this temperature and within 109 days of moldboard plowing, average SIN concentrations were 22.1 mg N/kg soil; 109 days or more past plowing average SIN dropped to 7.7 mg N/kg soil. Other drivers of SIN dynamics were N available from manure and cover crops. Highest average leachate NO3- N concentrations (15.2 ppm) occurred in fall and winter when SIN was above 4.9 mg/kg six weeks prior to leachate collection. Late season tillage operations leading to elevated SIN and leachate NO3- N concentrations were a strategy to reduce weeds while meeting consumer demand for organic products. Thus, while tillage that incorporates organic N inputs preceding cash crops can promote synchrony of N mineralization and crop demand, late or post-season tillage promotes NO3 leaching by stimulating SIN pulses that are asynchronous with plant uptake.

Particulate-matter emission estimates from agricultural spring-tillage operations using LIDAR and inverse modeling

Particulate-matter (PM) emissions from a typical spring agricultural tillage sequence and a strip–till conservation tillage sequence in California’s San Joaquin Valley were estimated to calculate the emissions control efficiency (η) of the strip–till conservation management practice (CMP). Filter-based PM samplers, PM-calibrated optical particle counters (OPCs), and a PM-calibrated light detection and ranging (LIDAR) system were used to monitored upwind and downwind PM concentrations during May and June 2008. Emission rates were estimated through inverse modeling coupled with the filter and OPC measurements and through applying a mass balance to the PM concentrations derived from LIDAR data. Sampling irregularities and errors prevented the estimation of emissions from 42% of the sample periods based on filter samples. OPC and LIDAR datasets were sufficiently complete to estimate emissions and the strip–till CMP η, which were ∼90% for all size fractions in both datasets. Tillage time was also reduced by 84%. Calculated emissions for some operations were within the range of values found in published studies, while other estimates were significantly higher than literature values. The results demonstrate that both PM emissions and tillage time may be reduced by an order of magnitude through the use of a strip–till conservation tillage CMP when compared to spring tillage activities.

Fall and Spring Tillage Effects on Sugarbeet Production

The ability to vary primary tillage timing between fall and spring for sugarbeet production could benefit producers by providing flexibility for when field work occurs and may allow earlier planting in the spring. This study was conducted to evaluate the effects of strip and conventional tillage conducted in the spring and fall under various N supply levels on sugarbeet production in the northwest U.S. The treatments included tillage time (fall and spring), tillage system (moldboard plow, chisel plow and strip tillage), and N supply (5 levels including a control). The study was conducted in Kimberly, ID in 2008 and 2009 on a Portneuf silt loam. Within each year and tillage type, estimated recoverable sucrose and root yields were not different between fall and spring tillage timings. These data suggest that sugarbeet growers in the northwest U.S. have flexibility in timing their tillage practices across various tillage systems.

Alternatives to neonicotinoid insecticides for pest control: case studies in agriculture and forestry.

Neonicotinoid insecticides are widely used for control of insect pests around the world and are especially pervasive in agricultural pest management. There is a growing body of evidence indicating that the broad-scale and prophylactic uses of neonicotinoids pose serious risks of harm to beneficial organisms and their ecological function. This provides the impetus for exploring alternatives to neonicotinoid insecticides for controlling insect pests. We draw from examples of alternative pest control options in Italian maize production and Canadian forestry to illustrate the principles of applying alternatives to neonicotinoids under an integrated pest management (IPM) strategy. An IPM approach considers all relevant and available information to make informed management decisions, providing pest control options based on actual need. We explore the benefits and challenges of several options for management of three insect pests in maize crops and an invasive insect pest in forests, including diversifying crop rotations, altering the timing of planting, tillage and irrigation, using less sensitive crops in infested areas, applying biological control agents, and turning to alternative reduced risk insecticides. Continued research into alternatives is warranted, but equally pressing is the need for information transfer and training for farmers and pest managers and the need for policies and regulations to encourage the adoption of IPM strategies and their alternative pest control options.

Mound measurements — quantifying medium-term soil erosion under olive trees in Northern Jordan

Over the last few decades many quantitative erosion studies have revealed that olive orchard expansion and increased mechanization in southern European countries have led to increased soil erosion under olive trees. Consequently, these studies have suggested different methods of mitigation. In light of the 2014 European trading zone expansion to countries east and south of the Mediterranean, a further intensification of olive plantations is postulated to meet market demands. To attain first medium-term estimates of erosion in Northern Jordan and its driving factors, a new method measuring olive mounds was implemented. Seven fields with clearly erosive structures were chosen throughout the Wadi Al-Arab catchment in Northern Jordan. Topographic measurements were used to reconstruct the historical and recent surface level and calculate the volume eroded since the planting of the trees. A total of 81 bulk density measurements and 14 tree cores allowed the estimation of the soil loss in tons per hectare. The combination of modified land use map and slope information helped to identify similar olive fields with high erosive potential.Results show that the method provides medium-term quantitative estimates for averaged soil loss consistent with some existing results from similar research areas in the Mediterranean. They clearly indicate the significant potential for erosion in olive orchards with around 95±8tha−1yr−1. Tillage practice and water erosion were identified as critical erosion processes, both depending on tillage characteristics, tillage timing, and soil parent material. The investigated fields represent about 19% of the catchment's surface area and are likely to contribute to the measured yearly sediment yield that fills up the Wadi Al-Arab reservoir with sediments.

Effect of time of autumn primary tillage on soil structure, grain yield and risk of nitrogen leaching in two Swedish clay soils

Delaying tillage and incorporation of arable crop residues in autumn may limit accumulation of soil mineral nitrogen (SMN) and reduce nitrogen (N) leaching. However, on clay soils, high water content during late tillage can impair soil structure and fertility. This study investigated the effects of tillage timing on SMN (0–90 cm depth), soil physical properties in the topsoil and yield in two Swedish clay soils differing in clay content. SMN generally increased during autumn and also with earlier tillage. On a heavy clay soil (Ultuna; ∼60% clay), SMN increased throughout winter until spring and the amount of N leached was probably small. In contrast, on a clay loam soil in southernmost Sweden (Rydsgård; ∼35% clay), SMN decreased during winter by up to 26 kg ha−1. In general, measured soil water content (w) was lower than 0.9 × plastic limit (PL) at the time of early tillage (mouldboard ploughing or stubble cultivation), while it exceeded 0.9 PL at the time of normal and late tillage. The proportion of small aggregates produced by tillage was negatively correlated to relative soil water content at the time of tillage (w/PL). Conventional methods to determine soil physical qualities (bulk density, saturated hydraulic conductivity, aggregate tensile strength) did not show any clear differences between treatments. However, plant emergence and yield were significantly reduced after late compared with early tillage at Ultuna, a trend that has persisted from 2000 until the present. These results suggest that the suitability of delayed autumn tillage as a means to reduce SMN accumulation and N leaching varies between Swedish clay soils. A reduction in N leaching can be achieved on lighter clay soils in warmer and moister areas, whereas the effects may be small on heavier clay soils in central Sweden, where repeated late tillage carries a risk of yield reduction.

Alfalfa Nitrogen Credit to First‐Year Corn: Potassium, Regrowth, and Tillage Timing Effects

Compared with corn (Zea mays L.) following corn, N guidelines for first‐year corn following alfalfa (Medicago sativa L.) in the U.S. Corn Belt suggest that N rates can be reduced by about 168 kg N ha−1 when ≥43 or 53 alfalfa plants m−2 are present at termination. These guidelines have been questioned by practitioners, however, as corn grain yields have increased. We conducted experiments at 16 locations in Minnesota to address questions regarding N availability to first‐year corn after alfalfa relating to the effect of carryover fertilizer K from alfalfa and the amount and timing of alfalfa regrowth incorporation. Corn grain yield, silage yield, and fertilizer N uptake were not affected by carryover K or amount or timing of regrowth incorporation. Maximum corn grain yield ranged from 12.0 to 16.1 Mg ha−1 among locations but responded to fertilizer N at only one. At that location, which had inadequate soil drainage, the economically optimum N rate (EONR) was 85 kg N ha−1, assuming prices of US.87 kg−1 N and US$132 Mg−1 grain. The EONR for silage yield across 6 of 15 locations where it was measured was 40 kg N ha−1, assuming US$39 Mg−1 silage. These results demonstrate that on highly productive medium‐ to fine‐textured soils in the Upper Midwest with ≥43 alfalfa plants m−2 at termination, first‐year corn grain yield is often maximized without fertilizer N, regardless of alfalfa regrowth management or timing of incorporation, but that small N applications may be needed to optimize silage yield.