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Crop sensing is a promising approach for predicting corn (Zea mays L.) yield. Yield prediction is the first step in development of algorithms for sensor-based N management. Here, we evaluated the impact of (i) timing of sensing (growth stage), and (ii) method of reporting sensor data on estimations of corn grain and silage yield in New York. Sensor data were reported as the normalized difference vegetation index (NDVI), in-season estimated yield (INSEY) expressed as NDVI divided by days after planting (DAP; INSEYDAP), growing degree days (GGD; INSEYGGD), and the inverse simple ratio (ISR; [1–NDVI]/[1+NDVI]) divided by DAP (INSEYISR). To evaluate timing of sensing, corn of six fertility trials was scanned at every growth stage between V4 and V11. The replicated trials had up to six N rates (0, 56, 112, 168, 224, and 336 kg ha–¹). The V7 sensor and yield data from zero-N plots of nine additional on-farm trials (varying histories) were added to derive yield algorithms for New York. Drought at three sites in 2016 negatively impacted the accuracy of sensor-based grain yield estimates (R² 0.70 (grain) and >0.77 (silage). We conclude that INSEY data obtained at V7 can be used to accurately predict corn grain and silage yields in non-drought conditions in New York.

Northeastern U.S. (New York, Pennsylvania, and New England states) dairy farmers are increasingly interested in improving soil health, nutrient sequestration, and dry matter production. Consequently, farmers ask about managing winter cover crops (WCCs) in corn silage (Zea mays L.) rotations. In this literature review we identify WCCs most suitable to the Northeast, and summarize studies on (i) fall and spring N accumulation, (ii) nitrogen fertilizer replacement value (NFRV) for the next corn crop, and (3) environmental and management variables that affect N uptake and NFRV. We also discuss the literature on use of WCCs as forage commodity crops. Overwintering species most suitable for corn silage rotations are wheat (Triticum aestivum L.), cereal rye (Secale cereale L.) and triticale (X Triticosecale Wittm.). Clover (Trifolium spp.) and vetch (Vicia spp.) can add N but require inter-seeding in the Northeast. The NFRV for vetch typically exceeds that of clover, while the NFRVs of winter cereals tend to be low or negative. A few studies suggest cover crop termination with herbicides compared to tillage incorporation can, when no fertilizer N or manure is added, result in slower decomposition and more gradual N release. Research on the effects of tillage on NFRVs of cover crops is inconclusive. When seeded after corn silage, cereal rye is most effective in N uptake in fall and spring. A corn rotation that includes cereal rye or triticale that can be harvested has the potential to reduce soil erosion, capture residual N, increase annual forage yields, and provide quality forage.

Published in Agron. J. 106:871–880 (2014) doi:10.2134/agronj13.0286 Copyright © 2014 by the American Society of Agronomy, 5585 Guilford Road, Madison, WI 53711. All rights reserved. No part of this periodical may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or any information storage and retrieval system, without permission in writing from the publisher. ABSTRACT

Current New York land grant university fertility guidelines for corn (Zea mays L.) recommend the use of 22 to 34 kg N ha -1 of band-applied starter fertilizer. On-farm research was conducted in 2006 and 2007 on a western New York dairy farm with an alfalfa (Medicago sativa L.)-corn rotation to evaluate the need for starter N for corn in regularly manured fields. In 2009, the study was expanded to include 21 fields varying in soil type, manure history, and soil N supply potential as expressed by the Illinois soil N test (ISNT). At the western New York farm, there was no increase in corn silage yield or quality with starter N use in first-, second-, or fourth-year corn fields. The results of the statewide assessment also showed that for fields with optimal ISNT-N, manure could replace starter N without a decline in corn silage yield or quality. Starter N fertilizer application was needed for optimal yield in fields deficient or marginal in ISNT-N and without a manure history. For such fields, manure could replace the need for starter N as long as sufficient N was applied with the manure, indicated by corn stalk NO 3 test (CSNT) results between 750 and 2000 mg NO 3 -N kg -1 . A response of silage yield to starter N was common when CSNT-N was

We studied the impact of semisolid dairy manure application rate and timing on yield and nutritive value oforchardgrass (Dactylisglomerata L.). Manure was applied at spring greenup and after all three harvests in seven treatment combinations, not exceeding 44.8 Mg ha -1 per application during the growing season. Recommended rate ofN fertilizer was also included as a treatment, and all treatments were applied for five growing seasons. A three-cut system was used, producing suitable forage for lactating dairy cows for cuts 1 and 2. Average dry matter (DM) yields for total seasonal manure applications of 44.8, 67.2, and 89.6 Mg ha -1 were 7.02, 7.89, and 9.10 Mg ha -1 , respectively. There was no significant effect of timing of manure applications on total DM yield, although there was a tendency for lower yields when manure was applied in the autumn. Manure applied at the seasonal rate of 179.2 Mg ha -1 resulted in greater DM yields than N fertilization by the second year of the study. Neither application rate nor timing of manure application had an impact on forage nutritive value. Strong correlations of neutral detergent fiber digestibility (NDFD), relative forage quality (RFQ), and kg milk Mg -1 of forage DM (Milk Mg -1 ) with in vitro true digestibility (IVTD) suggest that NDFD, RFQ, and Milk Mg -1 provide little additional information beyond what is found in IVTD. We conclude that from a forage yield and nutritive value standpoint, timing of seasonal manure applications to orchardgrass is not a critical issue.

Decomposition of forage legume-grass (FLG) sods after turnover will supply N to the next corn (Zea mays L.) crop. For optimum economic grain production typically a starter N application is sufficient. However, the impact of eliminating sidedress N on yield and quality of silage corn in the year after sod turnover (FYC) is not well documented and little is known about the effects of timing of sod turnover (fall or spring) or sod composition (percentage legume) on N fertilizer needs of FYC. In 2005 and 2006, 13 on-farm and three research station N trials were conducted throughout New York (NY) to determine (i) N needs for optimum yield and quality of FYC and (ii) the impact of FLG composition and timing of sod kill on the likeliness of an economic N fertilizer response. On-farm trials included four sidedress N rates (0, 56, 112, and 168 kg N ha -1 ) with a small, banded starter application (34 kg N ha -1 maximum). The three research sites also contained a no starter control. Eliminating the starter resulted in significantly lower yields while sidedress N did not increase yield at any of the 16 sites. Nitrogen application increased crude protein (CP) levels but did not affect other silage quality parameters or estimated milk production. The increase in CP came at great economic (fertilizer) and environmental (low apparent N recovery) costs. We conclude a small starter application is sufficient for optimum yield and quality of FYC regardless of timing of sod turnover or its composition.

Brown midrib (BMR) forage sorghum [Sorghum bicolor (L.) Moench.] 3 sudangrass (Sorghum sudanense Piper) hybrids (S 3 S) have been considered as a possible forage alternative to maize silage (Zea mays L.) where maize planting is delayed due to wet soil conditions. Our objective was to determine the most economic rate of nitrogen (MERN) for BMR S 3 S grown in a two-cut management system with a split application of N. Six field trials were conducted in New York in 2003 and 2004. One trial followed a grass–legume sod; a second trial had received liquid manure 19 mo before S 3 S planting. The remaining four followed S 3 S, silage maize, and/or a small grain crop. The MERN ranged from 137 to 192 kg N ha 21 cut 21 with dry matter (DM) yield ranging from 7.8 to 9.7 Mg ha 21 at the sites without additional N input. At the sites with prior N inputs, yield was higher (10.4–13.8 Mg ha 21 ) and MERN lower. The apparent nitrogen recovery (ANR) at the MERN was highest (61–73%) for the sites with prior N inputs. Nitrogen application rates . 145 kg N ha 21 cut 21 decreasednitrogenuseefficiency(NUE)to,15kgDMkg 21 N,whilethe ANR became ,45%. We concluded that the MERN for BMR S 3 S grown in New York in a two-cut system following maize, small grains, or forage S 3 S is 125 to 145 kg N ha 21 cut 21 . For sites that follow sod plow-down or recent manure application, N application rates should not exceed 40 to 60 kg N ha 21 cut 21 .

The presidedress nitrate test (PSNT) is currently the best tool available for Northeastern producers to determine if corn (Zea mays L.) will benefit from sidedress N. The PSNT requires 0- to 30-cm soil samples, which can be difficult to obtain on stony soils, and samples need to be taken in late-spring, an inopportune time for dairy (Bos taurus) farmers. Additionally, the in-season nature of the PSNT prevents its use by producers who apply preplant broadcast N. The Illinois soil N test (ISNT) is a simple test that estimates a potentially mineralizable fraction of soil organic N, amino sugar N. The test was able to identify sites that are nonresponsive to sidedress N fertilization in Illinois. From 2002 to 2004, 33 field trials were conducted to assess the effectiveness of the ISNT as compared with the PSNT in New York. Results confirmed the ability of the PSNT to separate responsive from nonresponsive corn sites. The ISNT was not an effective predictor by itself. However, when ISNTresults and soil organic matter (OM) were considered, critical values could be developed that separated fields that were responsive to sidedress N from nonresponsive sites for corn silage dry matter yield, N concentration, N uptake, and estimated milk yield (kg of milk per ha predicted based on yield and quality of the silage). Further evaluation of the ISNT with consideration for OM could improve the accessibility of soil N testing to corn producers who apply N as sidedress as well as those who fertilize with preplant broadcast applications in the Northeast.