Manjula Nathan

Reducing Phosphorus Loss in Tile Water with Managed Drainage in a Claypan Soil

Installing subsurface tile drain systems in poorly drained claypan soils to improve corn ( L.) yields could potentially increase environmental phosphorus (P) loss through the tile drainage system. The objectives of the study were to quantify the average concentration and loss of ortho-P in tile drain water from a claypan soil and to determine whether managed subsurface drainage (MD) could reduce ortho-P loss in tile water compared with free subsurface drainage (FD). Flow-weighted ortho-P concentration in the tile water was significantly lower with MD (0.09 mg L) compared with that of FD (0.15 mg L). Ortho-P loss in the tile water of this study was reduced with MD (36 g ha) by 80% compared with FD (180 g ha). Contrary to previous research, reduced ortho-P loss observed over the 4-yr study was not solely due to the reduced amount of water drained annually (63%) with MD compared with FD. During the spring period, when flow was similar between MD and FD, the concentration of ortho-P in the tile water generally was lower with MD compared with FD, which resulted in significantly less ortho-P loss with MD. We speculate that MDs ability to conserve water during the dry summer months increased corns uptake of water and P, which reduced the amount of P available for leaching loss in the subsequent springs.

Corn Production as Affected by Phosphorus Enhancers, Phosphorus Source and Lime

Prompted by high cost of fertilizer, farmers are investigating ways to enhance the efficiency of phosphorus (P) fertilizers. This study examined the effects of liming application (0 Mg ha -1 and recommended rate), P source [non-treated control and a broadcast application of diammonium phosphate (DAP) or triple superphosphate (TSP)], and the presence or absence of two commercial enhanced efficiency P products (Avail ® and P2O5-Max ® ) on corn (Zea mays L.) production. The study was conducted at Novelty in northeastern Missouri and Portageville in southeastern Missouri. The P enhancers did not affect plant population, silage dry weights, grain moisture, yield, protein, oil, or starch concentrations at either location. At Portageville, P enhancers did not affect plant N, P, K uptake and apparent P recovery efficiency (APRE). At Novelty, neither P enhancer paired with DAP increased P uptake over the non-treated control. TSP treated with Avail

Increased access to soil testing databases through the world wide web: opportunities and issues

Soil testing laboratories throughout the United States have assisted agricultural producers to more efficiently manage soil nutrient amendments since the 1940s. Information generated during soil testing, such as client and sample information, and results of soil analyses and nutrient recommendations, are maintained in records referred to collectively as the soil testing database. The purpose of this paper is to discuss current and potential uses of soil testing databases and issues associated with increased access to this environmental information through electronic media such as the World Wide Web. Current uses of soil testing databases include determining general trends in nutrient levels on county, state or regional scales, evaluating the performance of the soil testing laboratory and testing for relationships among soil properties. Typically, public access to soil testing databases is restricted to annual summaries which protect the confidentiality of individual soil test clients. However, in an effort to improve services for clients, soil testing laboratories have begun to use the World-Wide Web to provide clients and other authorized individuals password-protected access to soil testing results. Possible additional benefits of web-based access are the opportunity to facilitate client feedback and to provide decision support programs and information for clients. Other potential uses of the soil testing database could be progressively more intrusive on the privacy rights of soil test clients, including commercial marketing of fertilizer products and evaluation of compliance with environmental regulations. Issues of privacy and ownership of environmental information first may need to be addressed, possibly through legislation, before soil-testing databases can be fully utilized without inhibiting public participation in soil testing programs. We envision that once appropriate policies and safeguards are developed to protect the rights of clients, soil testing databases could be part of an interactive and centralized geographically referenced database that integrates available information, promotes more rapid communication, and provides low-cost and customized client decision support in environmental and agricultural management.

Foliar Potassium Fertilizer Additives Affect Soybean Response and Weed Control with Glyphosate

Research in 2004 and 2005 determined the effects of foliar-applied K-fertilizer sources (0-0-62-0 (%N-%P2O5-%K2O-%S), 0-0-25-17, 3-18-18-0, and 5-0-20-13) and additive rates (2.2, 8.8, and 17.6 kg K ha−1) on glyphosate-resistant soybean response and weed control. Field experiments were conducted at Novelty and Portageville with high soil test K and weed populations and at Malden with low soil test K and weed populations. At Novelty, grain yield increased with fertilizer additives at 8.8 kg K ha−1 in a high-yield, weed-free environment in 2004, but fertilizer additives reduced yield up to 470 kg ha−1 in a low-yield year (2005) depending on the K source and rate. At Portageville, K-fertilizer additives increased grain yield from 700 to 1160 kg ha−1 compared to diammonium sulfate, depending on the K source and rate. At Malden, there was no yield response to K sources. Differences in leaf tissue K , S , B , and Cu concentrations among treatments were detected 14 d after treatment at Novelty and Malden. Tank mixtures of K-fertilizer additives with glyphosate may provide an option for foliar K applications.

Evaluation of Modified Mehlich and Sikora Buffer Methods as an Alternative to Modified Woodruff Buffer in Determining Lime Requirement for Missouri Soils

The modified Woodruff buffer (MWB) test is used to determine lime requirement (LR) for Missouri soils. Though this method is proven to work for Missouri soils, it uses p-nitrophenol, which is a hazardous substance. Soil-testing laboratories are under increasing pressure to reduce hazardous wastes, which must be collected and disposed of following U.S. Environmental Protection Agency protocols. The goal of this study was to evaluate the modified Mehlich buffer (MMB) and the Sikora buffer (SB) as alternatives to the MWB in determining the LR for Missouri soils. Thirty soils were collected from major agricultural areas in Missouri, treated with calcium carbonate (CaCO3), and incubated for 90 days. Soil pHs [0.01 M calcium chloride (CaCl2) 1:1] was regressed against CaCO3 rate, and the actual LR was estimated for each soil to raise the soil pHs to target levels of 5.8, 6.3, and 6.8. The MWB, MMB, and SB pHs were regressed against the actual LR for all 30 soils to evaluate the effectiveness of each test for estimating the LR. The MMB and SBs were found to be as good as or better than MWB in predicting LR in Missouri soils. Both buffers (MMB and SB) were found to be equally effective in generating accurate estimates of the LR to raise soils to pHS 5.8, 6.3, and 6.8 (for pH values 5.8: R2 = 0.76, 0.82, 0.81; for pH values 6.3: R2 = 0.80, 0.88, 0.86; and pH values 6.8: R2 = 0.77, 0.89, 0.87 for MWB, MMB, and SB, respectively). A test to evaluate the stability of the buffers over time indicated that MMB had the shortest bench life (about 21 days) when compared to the MWB and SB, thus making it less feasible for use by soil test laboratories. Based on performance and stability, SB is a better alternative than MWB for Missouri soils.