Considerable interest exists in New York for narrow row corn (Zea mays L.) silage production because farmers, who converted from 30‐ to 15‐in. row spacing, report yield increases of 3 to 4 tons/acre. We evaluated eight hybrids at densities of 18 000, 24 000, 30 000, 36 000, and 42 000 plants/acre in 1994, 1995, and 1996 to compare yield, quality, and economics of corn silage production at 15‐ and 30‐in. row spacings. When averaged across years, hybrids, and densities, corn silage yielded 24.9 tons/acre at 15 in. and 23.9 at 30 in. row spacing. Row spacing × hybrid and row spacing× plant density interactions did not exist. When averaged across years, hybrids, and row spacings, maximum economic yields occurred at about 39 500 plants/acre. In vitro true digestibility (IVTD), however, had a 0.1% decrease and neutral detergent fiber (NDF) had a 0.13% increase per 1000 plant/acre increase. Consequently, estimated maximum economic milk yield occurred at about 35 000 plants/acre. Partial budget analyses indicated that farmers who produce 200 acres of corn silage might expect a slight loss in annual net farm income (−$696) with the conversion from 30‐ to 15‐in. row spacing. Farmers, who produce 400 and 800 acres of silage, might expect modest ($3116) and significant gains ($11 624) in annual net farm income, respectively. We have initiated field‐scale trials on a dairy farm to further assess the potential for narrow row corn silage production in New York. Research Question Considerable interest exists in New York for narrow row corn silage production because silage producers, who have converted from 30‐ to 15‐in. row spacing, report 3 to 4 tons/acre greater yields. Narrow row corn silage producers in New York plant at 45 000 to 50 000 kernels/acre because on‐farm observations suggest that corn responds best to 15‐in. rows under high populations. Unfortunately, limited documented research exists on the yield, quality, and economics of corn silage production under narrow rows and high populations. Objectives of this study were to: (i) compare yield and quality characteristics of corn silage production at 15‐ and 30‐in. row spacings, (ii) determine whether row spacing × hybrid interactions exist for yield and quality, (iii) determine whether row spacing × plant density interactions exist for yield and quality, and (iv) evaluate the economics of converting from 30‐ to 15‐in. row spacings in New York. Literature Summary Recent narrow row corn research reported about a 4% average grain yield response to narrow rows with no spacing by plant density interaction. Grain corn, however, had about an 8% average yield response to narrow rows in northern latitudes. No recent published research has evaluated corn silage yield and quality characteristics under narrow rows. Studies in the late 1960s and early 1970s reported inconsistent yield responses to narrow rows. A study in Georgia reported greatest silage yields under narrow rows and high densities at one site, but under wide rows and low densities at another site. A study in New Yor...
The HYDRUS-2D model was experimentally verified for water and salinity distribution during the profile establishment stage (33 days) of almond under pulsed and continuous drip irrigation. The model simulated values of water content obtained at different lateral distances (0, 20, 40, 60, 100 cm) from a dripper at 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 120, 140 and 160 cm soil depths at different times (5, 12, 19, 26 and 33 days of profile establishment) were compared with neutron probe measured values under both irrigation scenarios. The model closely predicted water content distribution at all distances, times and soil depths as RMSE values ranged between 0.017 and 0.049. The measured mean soil water salinity (ECsw) at 25 cm from the dripper at 30, 60, 90 and 150 cm soil depth also matched well with the predicted values. A correlation of 0.97 in pulsed and 0.98 in continuous drip systems with measured values indicated the model closely predicted total salts in the root zone. Thus, HYDRUS-2D successfully simulated the change in soil water content and soil water salinity in both the wetting pattern and in the flow domain. The initial mean ECsw below the dripper in pulsed (5.25 dSm -1 ) and continuous (6.07 dSm -1 ) irrigations decreased to 1.31 and 1.36 dSm -1 , respectively, showing a respective 75.1 and 77.6% decrease in the initial salinity. The power function [y = ax -b ] best described the mathematical relationship between salt removal from the soil profile as a function of irrigation time under both irrigation scenarios. Contrary to other studies, higher leaching fraction (6.4-43.1%) was recorded in pulsed than continuous (1.1-35.1%) irrigation with the same amount of applied water which was brought about by the variation in initial soil water content and time of irrigation application. It was pertinent to note that a small (0.012) increase in mean antecedent water content (h i ) brought about 8.25-9.06% increase in the leaching fraction during the profile establishment irrespective of the emitter geometry, discharge rate, and irrigation scenario. Under similar h i , water applied at a higher discharge rate (3.876 Lh -1 ) has resulted in slightly higher leaching fraction than at a low discharge rate (1.91 Lh -1 ) under pulsing only owing to the variation in time of irrigation application. The influence of pulsing on soil water content, salinity distribution, and drainage flux vanished completely when irrigation was applied daily on the basis of crop evapotranspiration (ETc) with a suitable leaching fraction. Therefore, antecedent soil water content and scheduling or duration of water application play a significant role in the design of drip irrigation systems for light textured soils. These factors are the major driving force to move water and solutes within the soil profile and may influence the off-site impacts such as drainage flux and pollution of the groundwater.
Phosphorus transfer in runoff from intensive pasture systems has been extensively researched at a range of scales. However, integration of data from the range of scales has been limited. This paper presents a conceptual model of P transfer that incorporates landscape effects and reviews the research relating to P transfer at a range of scales in light of this model. The contribution of inorganic P sources to P transfer is relatively well understood, but the contribution of organic P to P transfer is still relatively poorly defined. Phosphorus transfer has been studied at laboratory, profile, plot, field, and watershed scales. The majority of research investigating the processes of P transfer (as distinct from merely quantifying P transfer) has been undertaken at the plot scale. However, there is a growing need to integrate data gathered at a range of scales so that more effective strategies to reduce P transfer can be identified. This has been hindered by the lack of a clear conceptual framework to describe differences in the processes of P transfer at the various scales. The interaction of hydrological (transport) factors with P source factors, and their relationship to scale, require further examination. Runoff-generating areas are highly variable, both temporally and spatially. Improvement in the understanding and identification of these areas will contribute to increased effectiveness of strategies aimed at reducing P transfers in runoff. A thorough consideration of scale effects using the conceptual model of P transfer outlined in this paper will facilitate the development of improved strategies for reducing P losses in runoff.
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