Requirements For Corn Research Articles

Impact of the application of commercial and farm-made fermented liquid organic amendments on corn yield and soil quality

Organic amendments are being increasingly applied to agricultural soils as alternatives or complements to inorganic fertilizers. Organic amendments can increase the content of soil organic matter, concomitantly improving soil physical, chemical and biological properties. We evaluated the effect of the application of commercial vs. farm-made fermented liquid organic amendments, compared to mineral (NPK) fertilization, on corn yield and nutritional status, as well as on soil physicochemical and microbial properties as indicators of soil quality. In particular, we assessed the effect of two doses (optimal vs. suboptimal) and times of amendment application (basal dressing vs. basal + top dressing) for two consecutive growing seasons. Values of corn grain yield were lower in organically-amended plots than in those under NPK fertilization. At the optimal dose, the application of organic amendments led to significantly higher values of microbial activity (soil respiration; enzyme activities; potentially mineralizable N) and biomass (microbial biomass C, bacterial and fungal biomass), leading to an improvement in soil quality. The optimal application dose resulted in an enhanced soil nutrient pool. Conversely, soil properties were not significantly affected by the origin of the amendment (commercial vs. farm-made) or the time of application (basal dressing vs. basal + top dressing). 16S rRNA metabarcoding analysis revealed no significant changes in the diversity and composition of the soil prokaryotic communities between organically-amended and NPK-fertilized soils. It was concluded that the application of fermented liquid organic amendments at the optimal dose (according to the N requirements of corn) can be a beneficial agronomic practice for agricultural soil quality, posing a suitable alternative to mineral fertilization.

Legume Cover Crops Reduce Poultry Litter Application Requirements in Organic Systems

Organic farmers are challenged by increasing soil P levels resulting from the use of manure to meet cash crop N needs. The use of a legume cover crop may address this challenge. In a 2‐yr study at three organic production sites in Maryland, we examined the combination of a winter annual legume cover crop (hairy vetch, crimson clover, Austrian winter pea, and a no‐cover control) at three poultry litter (PL) application rates (to meet the N requirement of corn, to replace P removed by corn grain harvest, and a no‐PL control). Cover crop biomass varied by site and by year, ranging from about 600 to 6100 kg ha–1 for crimson clover. Cover crop N accumulation ranged from 15 to 169 kg N ha–1. Corn yields, which ranged from 2.9 to 14.2 Mg ha–1, tended to be lowest in the control (0 PL) no‐cover treatments and similar in the N‐based and P‐based treatments irrespective of the cover crop species. These results indicate that when legume cover crops are used, PL can be applied at a P‐replacement rate on sites with a history of PL application to meet crop production and environmental stewardship goals.Core Ideas Legume cover crop N accumulation ranged from 15 to 169 kg N ha–1. Corn yield after legume crops was not affected by poultry litter application rate. Legume cover crops provide opportunity to reduce poultry litter application rates.

Kajian Kebutuhan Air Irigasi Tanaman Jagung (Zea mays L.) Berdasarkan KP-01 dan Metode Thornthwaite-Mather

<p class="JudulAbstrakInggris">Two different methods for determining irrigation water requirement for corn, is KP-01 and Thornthwaite-Mather method. Two Methods have different parameter such as reference crop evapotranspiration (ETo) and effective rainfall. The average ETo value using Penman-Monteith for Thornthwaite-Mather was lower (82,5%) than using Penman Modification method (KP-01) . The ratio of effective rainfall between KP-01 and Thornthwaite-Mather was 33,02%. Corn water irrigation requirement for a pattern planting based on KP-01 is 806,96 mm, while corn water irrigation requirement based on Thornthwaite-Mather method is 254,4125 mm. Corn water irrigation requirement using KP-01 is higher than Thornthwaite-Mather because effective rainfall method for KP-01 (using USDA Soil Conservation Service) is lower than rainfall effective for Thornthwaite-Mather.</p>

Application of Machine Learning Methodologies for Predicting Corn Economic Optimal Nitrogen Rate

Core Ideas A Machine Learning approach was innovatively used to predict corn EONR. Two features were created to approximate hydrological conditions for modeling EONR. Soil hydrology conditions were found essential in successful modeling in‐season EONR. Determination of in‐season N requirement for corn (Zea mays L.) is challenging due to interactions of genotype, environment, and management. Machine learning (ML), with its predictive power to tackle complex systems, may solve this barrier in the development of locally based N recommendations. The objective of this study was to explore application of ML methodologies to predict economic optimum nitrogen rate (EONR) for corn using data from 47 experiments across the US Corn Belt. Two features, a water table adjusted available water capacity (AWCwt) and a ratio of in‐season rainfall to AWCwt (RAWCwt), were created to capture the impact of soil hydrology on N dynamics. Four ML models—linear regression (LR), ridge regression (RR), least absolute shrinkage and selection operator (LASSO) regression, and gradient boost regression trees (GBRT)—were assessed and validated using “leave‐one‐location‐out” (LOLO) and “leave‐one‐year‐out” (LOYO) approaches. Generally, RR outperformed other models in predicting both at planting and split EONR times. Among the 47 tested sites, for 33 sites the predicted split EONR using RR fell within the 95% confidence interval, suggesting the chance of using the RR model to make an acceptable prediction of split EONR is ∼70%. When RR was used to test split EONR prediction with input weather features surrogated with 10 yr of historical weather data, the model demonstrated robustness (MAE, 33.6 kg ha−1; R2 = 0.46). Incorporating mechanistically derived hydrological features significantly enhanced the ability of the ML procedures to model EONR. Improvement in estimating in‐season soil hydrological status seems essential for success in modeling N demand.

Nitrogen Dynamics in Living Mulch and Annual Cover Crop Corn Production Systems

White clover (living mulch), crimson clover, and rye cover crops were used for corn production. Plant‐available N was determined for each cover crop system to estimate N release. Soil N forms and the timing of N availability varied among the cover crops. Internal N use was similar but partial factor productivity and partial nutrient balance was greatest in the living mulch cover crop. Successful living mulch (LM) systems may be capable of meeting the N requirements of corn (Zea mays L.) despite competition during corn development. This study compared corn N dynamics in a perennial white clover (Trifolium pratense L.) LM system and annual cereal rye (Secale cereale L.) (CR) and crimson clover (Trifolium incarnatum L.) (CC) systems. Corn in the LM, CC, and CR cover crop systems received 56, 168, and 280 kg N ha−1, respectively. The mean total N provided from the cover crops was 145, 105, and 25 kg ha−1 in the LM, CC, and CR cover crop systems, respectively. Water uptake by the LM reduced soil water content, soil N availability, N uptake, and plant‐available N (PAN) compared with the CC and CR cover crop systems. Average grain yield was 10.4, 13.3, and 13.0 Mg ha−1 for the LM, CC, and CR cover crop systems, respectively. Nitrogen internal utilization efficiency was not different among systems, but fertilizer N partial nutrient balance and partial factor productivity was greatest for LM and least for CR. Overall, the LM system had lower soil N availability, grain yield, and PAN, but it supplied a significant amount of legume N to corn and minimized the need for mineral N. We concluded that success of the LM system is dependent on N mineralization of the white clover residue and that yearly weather variation significantly affects mineralization of cover crop residues and PAN.

Fertilization of high-yield corn with poultry litter based on nitrogen doses

Abstract: The objective of this work was to recommend nitrogen doses from poultry litter-based organic fertilizers in powder and pellet forms, compared with mineral fertilizer, in a high-yield corn crop under no-tillage. The treatments consisted of a 3×3+1 factorial arrangement, with: three fertilizers, two organic derived from poultry litter in powder (OPo) and pelletized (OPe) forms and one mineral fertilizer (M); three N doses of 65, 100, and 135% of the recommended N requirement for corn; and an unfertilized control. After five corn crops farmed under no-tillage in a Rhodic Kandiudox, the recommended doses for fertilization with poultry litter organic fertilizers, with an expected yield equal to or greater than 8,000 kg ha-1, could be achieved from doses of 100 kg ha-1 N in OPe and M and of 121 kg ha-1 N in OPo. Increasing doses of the OPe, OPo, and M fertilizers raise the contents of organic carbon, N, and available P in the surface soil layer (0.0-0.1 m) and of exchangeable K up to a depth of 0.2 m, allowing to obtain N, P, and K contents in the plant tissue within the sufficiency range of the corn crop.

Effect of Legume Cover Crops and Nitrogen Fertilization Rates on Yield and Nitrogen Use Efficiency of Waxy Corn (Zea mays L.) in No-Tillage System

The adoption of legume cover crops in no-tillage system can contribute to improve soil fertility by providing several benefits, including reduction in soil erosion, suppression of weed growth and N supply to subsequent crops. We conducted a field study to investigate the effect of cover crops and nitrogen fertilization rates on yield and nitrogen use efficiency of waxy corn (Zea mays L.) in no-tillage upland field. Two legume cover crops, hairy vetch (Vicia villosa Roth) and crimson clover (Trifolium incarnuturn L.) were mechanically terminated with roller in early June. For each cover crop treatment, nitrogen (N) fertilizer was applied at three different rates (145, 72.5 and 0 kg N ha-1 ). The growth and yield characteristics of corn were significantly affected by the N fertilization rates in crimson clover plots, which suggest N mineralization from the cover crop residue was not sufficient. In contrast, N fertilization rates had no significant effect on growth and yield of corn in hairy vetch plots, indicating that the amount of N released from the cover crop is large enough to meet most of the N requirement of corn. However, the application of N fertilizer in hairy vetch cover plots resulted in slight increase of crop yield, though not statically significant, and high levels of N concentration in corn plant tissue possibly due to luxury consumption of N. Organic residues on the soil surface in hairy vetch cover plots had substantial amounts of N after harvest, ranging from 100 to 116 kg N ha -1 , which is presumably retained during winter season and released by microbial mineralization in subsequent year. The highest nitrogen yield efficiency was achieved in the plot with hairy vetch cover and no N fertilizer application, followed by the plot with hairy vetch cover and 72.5 kg N ha -1 fertilization rate. In conclusion, hairy vetch showed better performance in corn productivity as compared with crimson clover. In addition, it was concluded that the application of N fertilizer between 0 and 72.5 kg N ha -1 in combination with hairy vetch cover crop might be most efficient for corn yield under no-tillage system with climatic and soil characteristics similar to those of the experimental site.

Emission of Volatile Organic Compounds as Affected by Rate of Application of Cattle Manure

<abstract> Beef cattle manure can serve as a valuable nutrient source for crop production. However, emissions of volatile organic compounds (VOCs) following land application may pose a potential off-site odor concern. This study was conducted to evaluate the effects of land application method, N application rate, soil moisture content, and time since manure application on VOC emissions. Manure from cattle fed a diet containing 30% wet distillers grains was applied to a cropland area at rates required to meet the 0.5, 1, or 2 year N requirement for corn. Land application methods included surface-applying manure (i.e., no tillage) or incorporating manure using disk tillage. The effect of soil moisture content on VOC emissions was determined by adding water to the experimental plots approximately 24 h after manure application. Volatile sulfur compounds (i.e., dimethyl disulfide and dimethyl trisulfide), isovaleric acid, and butyric acid contributed 43.4%, 14.0%, and 13.9%, respectively, of the total measured odor activity value (OAV). Emissions of each of the principal VOC odor compounds were reduced by manure incorporation. In general, no significant differences in VOC measurements of volatile fatty acids (VFAs) and aromatic compounds were found among varying manure application rates. However, an increase in emissions of volatile sulfur compounds resulted from increased manure application. Measurements of VFAs and aromatic compounds usually decreased and sulfide emissions increased following the application of water. Application method, N application rate, soil moisture content, and time since application may all influence VOC emissions following land application of cattle manure.

The influence of climate change on irrigation water requirements for corn in the coastal region of Ecuador

This study investigated the irrigation water requirements (IWR) for corn in five provinces of the coastal region of Ecuador that have been influenced by climate change. The weather data were statistically downscaled from six General Circulation Models and compared with the current climate period from 1986 to 2012. CROPWAT 8.0 was used to estimate future IWR for corn cultivation from 2011 to 2100 based on the Representative Concentration Pathways 4.5 and 8.5 scenarios. Also the frequency of predicted rainfall for future periods was analysed to identify the possibility of obtaining the amount of water required for corn plantation from rainfall. The projected trend of future climate showed increases in temperature and rainfall. The predicted IWR showed a decreasing trend in the rainy season and a similar or slightly lower trend in the dry season. Sufficient rain for corn cultivation was predicted for the wet region of the study area, with lower IWR, whereas most of the dry region was shown to have similar patterns of current water demands, except an increase in predicted rainfall resulted in lower IWR in some parts of this region.

Increasing corn yield with no-till cropping systems: a case study in South Dakota

AbstractNo-till practices have improved crop yields in the semiarid Great Plains. However, a recent assessment of research studies across the globe indicated that crop yields are often reduced by no-till. To understand this contrast, we examined corn yields across time in a no-till cropping system of one producer in central South Dakota to identify factors associated with increased yield. The producer started no-till in 1990; by 2013, corn yield increased 116%. In comparison, corn increased only 32% during this interval with a conventional, tillage-based system in a neighboring county. With no-till, corn yields increased in increments due to changes in management. For example, corn yield increased 52% when crop diversity in the rotation was expanded from 2 to 5 crops. A further 18% gain in yield occurred when dry pea was grown before corn in sequence. Nitrogen (N) requirement for corn is 25% lower in no-till compared with a tillage-based rotation. Furthermore, phosphorus (P) fertilizer input also has been reduced 30% after 20 yr of no-till, even with higher yields. Our case study shows that integrating no-till with crop diversity and soil microbial changes improves corn yield considerably. This integration also reduces need for inputs such as water, N and P.

Spatial variability of soil acidity attributes and the spatialization of liming requirement for corn

In Brazil, technicians, in most cases, ignore the aspects related to the spatial variability of the soil acidity attributes when liming requirement is calculated. The objective of this study was to validate the liming practice, evaluating the presence of spatial variability of the soil acidity attributes and the existence of areas with differentiated liming requirement, which were calculated by different methods. The experiment was carried out in an area cultivated with corn under conventional management and irrigation. The soil (0-0.2 m) was sampled in a conventional way (composite soil sample) and in a systematic scheme, by use of a grid sampling. In sequence to the soil fertility attributes analysis, it was calculated the liming requirement, according to the methods of SMP pH, aluminum neutralization and elevation of soil Ca and Mg levels, and increase of the soil base saturation. After the descriptive analysis of the data set was accomplished, the semivariograms were calculated and the maps were obtained through the kriging technique. Absence of spatial dependence, as well as the non necessity of limestone application, was observed for the Al neutralization calculation method. Spatial dependence was only verified for the soil acidity attributes and to the liming requirement calculated by the base saturation and SMP pH methods; for these two methods, the semivariogram ranges obtained varied from 35.7 to 200.5 m. The results have highlighted the existence of differentiated liming requirement zones when the variability of the soil acidity attributes was considered in the calculation of the dose and type of limestone to be used for corn soil acidity correction.

Maize allergy: what we have learned so far

Maize allergy: what we have learned so far

Evaluating Multiple Indices from a Canopy Reflectance Sensor to Estimate Corn N Requirements

With the increasing cost of fertilizer N, there is a renewed emphasis on developing new technologies for quantifying in‐season N requirements for corn (Zea mays L.). The objectives of this research are (i) to evaluate different vegetative indices derived from an active reflectance sensor in estimating in‐season N requirements for corn, and (ii) to consider the influence of the N:Corn price ratio on the economic optimum nitrogen rate (EONR) developed using these indices. Field experiments were conducted at eight site‐years in central Pennsylvania. A two‐way factorial experiment was implemented as a split‐plot randomized complete block (four blocks) design, with different rates of N applied (i) at planting (NPL) to create a range of N supply, corn color, and radiance; and (ii) at V6 (NV6) to measure yield response to NV6. Canopy reflectance measurements were obtained using a Crop Circle (Holland Scientific, Lincoln, NE) sensor just before NV6 applications, and grain yield was determined at harvest. The EONR was determined using a quadratic‐plateau yield response function for price ratios from zero to 14:1, then regressed on 21 combinations of absolute and relative spectral bands and indices. The EONR at V6 at 6:1 price ratio ranged from 0 to 221 kg ha−1 among the eight site‐years, with a mean of 69 kg ha−1 Better prediction of EONR was obtained by indices calculated relative to a high N plot rather than absolute indices. Relative Green Difference Normalized Vegetation Index by ratio (RGNDVIR) was the best predictor of EONR at V6 when expressed as a linear‐floor model (R2 of 0.79). A relationship was developed so that EONR estimates derived using the Crop Circle sensor could be easily adjusted based on the current N:Corn price ratio. When N requirements are high (RGNDVIR = 0.8) and if the price ratio changes from 4:1 to 10:1, the EONR would change from 267 to 214 kg ha−1 N.

Sediment and Nutrient Losses from Field-Scale Cropland Plots Treated With Animal Manure and Inorganic Fertilizer

A field-scale plot study was conducted at Virginia Tech's Prices Fork Research Farm, to evaluate the transport of nutrients in runoff from manure and fertilizer applied at P-based agronomic rates to cropland planted to corn. Simulated rainfall events representing 2- to 10-year storms in southwest Virginia, occurring 1 and 2 days following manure and fertilizer application were used to generate runoff. Plots were treated with surface applied poultry litter, surface applied and incorporated dairy manure, incorporated inorganic fertilizer, and no fertilizer (control). Application rates were based upon agronomic phosphorus (P) requirements of corn. The concentration of total suspended solids and nutrients decreased from the first to the second simulated rainfall event; however, the edge-of-field mass loss or yield increased due to increased runoff volume. Surface application of dairy manure resulted in 25–50% lower runoff volumes and 35–60% lower total suspended solid yields when compared to surface applied poultry litter. Surface applied poultry litter produced the greatest total P and dissolved reactive P losses. Results of this study suggest that manure applied based on crop P requirements can still yield significant edge-of-field nutrient losses, if rainfall occurs soon after application.

Aerial Color Infrared Photography for Determining Early In‐Season Nitrogen Requirements in Corn

In‐season determination of corn (Zea mays L.) N requirements via remote sensing may help optimize N application decisions and improve profit, fertilizer use efficiency, and environmental quality. The objective of this study was to use aerial color‐infrared (CIR) photography as a remote‐sensing technique for predicting in‐season N requirements for corn at the V7 growth stage. Field studies were conducted for 2 yr at three locations, each with and without irrigation, in the North Carolina Coastal Plain. Experimental treatments were a complete factorial of four N rates at planting (NPL) and five N rates at V7 (NV7). Aerial CIR photographs were taken at each of the locations at V7 before N application. Optimum NV7 ranged from 0 to 207 kg N ha−1 with a mean of 67 kg N ha−1. Significant but weak correlations were observed between optimum NV7 rates and the band combinations relative green, Relative Green Difference Vegetation Index, and Relative Difference Vegetation Index as measured in CIR photos. High proportions of soil reflectance in the images early in the corn growing season (V7) likely confounded our attempts to relate spectral information to optimum NV7 rates. The primary obstacles to applying this technique early in the season are the use of relative digital counts or indices that require high‐N reference strips in the field and strong background reflectance from the soil. When the NPL treatments that were nonresponsive to NV7 (i.e., optimum NV7 = 0) were removed from the analysis, the normalized near infrared, the Green Difference Vegetation Index, the Green Ratio Vegetation Index, and the Green Normalized Difference Vegetation Index were the best predictors of optimum NV7 rate (r2 = 0.33).

Aerial Color Infrared Photography for Determining Late‐Season Nitrogen Requirements in Corn

Fast and accurate methods of determining in‐season corn (Zea mays L.) N requirements are needed to provide more precise and economical management and potentially decrease groundwater N contamination. The objectives of this study were (i) to determine if there is a response to late‐season N applied to corn at pretassel (VT) under irrigated and nonirrigated conditions, and (ii) to develop a methodology for predicting in‐season N requirement for corn at the VT stage using aerial color infrared (CIR) photography. Field studies were conducted for 3 yr over a wide range of soil conditions and water regimes in the North Carolina Coastal Plain. Different fertilizer N rates were applied (i) at planting (NPL) to create a range of N supply, corn color, and near‐infrared (NIR) radiance; and (ii) at VT (NVT) to measure yield response to NVT. Aerial CIR photographs were obtained for each site at VT before N application. Significant grain yield responses to NPL and NVT were observed. Economic optimum NVT rates ranged from 0 to 224 kg ha−1 with a mean of 104 kg ha−1. Better prediction of economic optimum NVT rates was obtained with spectral band combinations rather than individual bands, and improved when calculated relative to high‐N reference strips measured at VT. The best predictor of economic optimum NVT (R 2 = 0.67) was a linear‐plateau model based on corn color and NIR radiance expressed using the Green Difference Vegetation Index (GDVI) relative to high‐N reference strips (Relative GDVI, RGDVI).

Corn Yield, Nitrogen Use, and Corn Rootworm Infestation of Rotations in the Northern Corn Belt

Crop rotation may improve production efficiency and reduce fertilizer N requirements for corn (Zea mays L.). Objectives were to determine effect of rotation and N on corn yield, efficiency of water use (WUE) and N use (NUE), and corn rootworm (Coleoptera: Chrysomelidae) beetle populations (CR). Rotations (started in 1990) were continuous corn (CC), corn–soybean [Glycine max (L.) Merr.] (CS), and a 4‐yr rotation of corn–soybean–spring wheat (Triticum aestivum L.) companion‐seeded with alfalfa (Medicago sativa L.)–alfalfa hay (CSWA). Nitrogen treatments for corn were corn fertilized for a grain yield of 8.5 Mg ha−1 (highN), 5.3 Mg ha−1 (midN), and no N fertilizer (noN). Average yield (1992–2003) was greatest (p = 0.003) under CS and highN (7.0 Mg ha−1). Yield differences (p = 0.001) among rotations increased with decreased fertilizer N. Average (1992–2003) yield with noN fertilizer was 5.8 Mg ha−1 under CSWA, 4.5 Mg ha−1 under CS, and 2.8 Mg ha−1 under CC. Nitrogen use efficiency differed (p = 0.096) only under midN with CSWA = CS &gt; CC. Soil water (upper 1.8 m) for corn measured on 1 June (average of N treatments) was 55, 54, and 45 cm for CC, CS, and CSWA, respectively. For CSWA under highN, available water limited yield in 3 of 6 yr. At highN, CR adult populations were greater under CS compared with CC and greater at higher N fertilizer levels within CC. Rotations have potential to improve production efficiency; however, there is potential for reduced corn yield after alfalfa due to less available soil water.

Soil tests for predicting the N requirement of corn

Several soil N tests were compared with the one currently used for predicting the N requirement for corn in Ontario. The current test involves a measurement of nitrate (NO3−, 0–30 cm) before N fertilizer sidedressing. The study was done to determine the efficacy of other tests for N fertilizer prediction. The tests chosen varied in the quantity of N “extracted” and included hot KCl-extractable NH4+, anaerobically released NH4+, extractable NH4+ following autoclaving in CaCl2 solution and total N of soil sampled to a depth of 30 cm. The 3-yr study was conducted on a sloped (simple) field site, which provided a wide range in soil organic matter (SOM) contents. A corn crop was grown each year following a barley crop with or without red clover cover crop residues incorporated in the spring and with or without N fertilization. Corn grain yields were obtained at the end of the growing season. Grain yields were lowest at the shoulder and backslope locations and highest at the footslope and toeslope locations. Corn plant shoot biomass and N content and soil mineral (NH4+and NO3−) N (0–30 cm) were measured biweekly to provide an estimate or index of available N. Plant and soil samples were taken at the summit, shoulder, backslope, footslope and toeslope locations providing a wide range of SOM levels, which, in turn, provided a range in available N for comparing the various soil N tests. The increase in estimated available N during the growing season was most rapid in the 120–180 day of year (DOY) period and substantially slower in the 230–260 DOY period. An available N index (AVN) was obtained by averaging the N measured with three plant and soil samples taken in the late August to early September period. Thus, the AVN was determined during a period when the increase in available N was relatively slow. Regressions of corn grain yield (not fertilized with N) on AVN produced R2 values ranging from 0.61 to 0.93. Values of R2 for AVN vs. the soil tests ranged from 0.34 to 0.88 where red clover crop residues were not involved. The AVN values were less correlated with the soil N test values where red clover cover crop residues were incorporated with R2 values ranging from 0.11 to 0.92. It was concluded that the hot KCl test would be a suitable alternative to the currently used soil NO3− test because of relatively simple soil sample preparations and storage, and analytical procedures. Key words: Soil N tests, corn, available N index, soil organic matter, landscape location

RESIDUAL EFFECTS OF COMPOST AND FERTILIZER APPLICATIONS ON NUTRIENTS IN RUNOFF

The application of compost or fertilizer at rates that exceed crop nutrient requirements can result in phosphorus(P) and nitrogen (N) accumulation in soil. This study was conducted to determine the influence of soil P and N contents onthe concentrations and total amounts of P and N transported in runoff. Composted beef cattle feedlot manure or inorganicfertilizer were added from 1992 to 1995 to a Sharpsburg silty clay loam soil at rates sufficient to meet P or N requirementsfor corn and incorporated following application. After four years of corn production following the last compost application,P concentration, EC, and pH of the surface soils on the Nbased compost treatments were significantly greater than the checkplots. Simulated rainfall was applied to the experimental site in 2000. Concentrations and total amounts of P and N in runoffwere similar on the compost and inorganic fertilizer plots. The application of corn residue at a rate of 6 Mg ha1 did notsignificantly affect the nutrient concentration of runoff or total nutrient transport when compared to a noresidue conditionfor a study site with a slope varying from 0.15% to 2.70%. On an adjoining field, compost or inorganic fertilizer were appliedat rates in excess of crop P and N requirements to increase soil test P levels. For Bray and Kurtz No. 1 soil test P levels rangingfrom 42 to 267 mg kg1 and watersoluble soil test P values varying from 5 to 61 mg kg1, the dissolved P (DP) concentrationof runoff did not correlate well with soil test P. Thus, factors other than soil test P appear to influence P loss in runoff forthe bare soil used in this investigation.

Residual effect of poultry litter applied to cotton in conservation tillage systems on succeeding rye and corn

The burgeoning poultry industry in the southeastern US is presenting a major environmental problem of safe disposal of poultry litter (PL). In a comprehensive study, we explored ways of PL use in conservation tillage-based cotton ( Gossypium hirsutum L.) production systems on a Decatur silt loam soil in north Alabama, from 1996 to 1999. The study reported here-in presents the residual effects of PL applied to cotton in mulch-till (MT) and no-till (NT) conservation tillage systems in 1997 and 1998 cropping seasons on N uptake, growth, and yield of rye ( Secale cereale, L.) cover crop and rotational corn ( Zea mays L.) in 1999. Rye was grown without additional N, whereas corn was grown at three inorganic N levels (0, 100, and 200 kg N ha −1). Poultry litter was applied to cotton in 1997 and 1998 at 0, 100, and 200 kg N ha −1. Residual N from PL applied to cotton in 1997 and 1998 produced up to 2.0 and 17.3 Mg ha −1, respectively, of rye cover crop and corn biomass (includes 7.1 Mg ha −1 of corn grain yield) without additional fertilizer. Therefore, in addition to supplying crop residues which reduce soil erosion, increase soil organic matter, and conserve soil moisture, the rye cover crop was able to scavenge residual N left by the cotton crop, which would otherwise, be at risk of being leached and pollute groundwater resources. Poultry litter applied to cotton also increased corn grain quality as shown by up to 100% increase in grain N content compared to the 0N treatment. Using PL with a slower rate of N release compared to inorganic fertilizer to meet some of the N requirements of corn, will not only reduce N fertilizer costs for corn, but will also reduce the risk of nitrate N leaching into groundwater. The maximum amount of crop residues added to the cotton based cropping system by residual N from PL and inorganic N was 21.3 Mg ha −1. This will lead to an increase in soil organic carbon and soil structure in the long term and a reduction in soil erosion, thereby further improving soil productivity, while at the same time, protecting the environment from nitrate pollution and soil degradation. Our study demonstrates that cotton under conservation tillage system in combination with rye cover crop and rotational corn cropping could use large quantities of PL thereby avoiding serious potential environmental hazards.