For the NIFA CEAP watersheds, nutrient management was successful when there was purposeful implementation of the practice, supported by education, outreach, and significant and constant financial incentives. This required human resources and financial capital. In watersheds where nutrient management plans were written, as they generally were, without significant local input, trusted advisors, and adequate resources, they frequently were unused.

Unintentional outcomes to water quality occurred when nutrient management behavior changed relative to placement, timing, and rate due to the adoption of conservation tillage. In the Rock Creek (Ohio) watershed, part of the Lake Erie basin, researchers measured significant reductions in total P found in water resources in the area after considerable adoption of conservation tillage (>60%) ( Richards et al., 2009 ). However, several years later, the trend in dissolved P increased dramatically. These increases were initially attributed to soil P stratification due to conservation tillage, which was believed to have substantially increased surface soil test P, which in turn would escalate dissolved P runoff ( Sharpley, 1980 ). Further investigation suggested that some tillage occurred and that stratification was not as great as expected. Farmers appeared to have changed their nutrient management behavior when they adopted conservation tillage: P applications moved away from the spring to the fall (timing), P fertilizer was applied on the surface rather than mixed into the soil (placement), and farmers applied P less often but in greater quantities (rate) ( Meals et al., 2012a ; Sharpley et al., 2012 ; Sharpley et al., 2013 ). Shifting nutrient management behavior, particularly for timing and rate, caused a shift from one pollutant form to another.

New York City's drinking water comes from multiple reservoirs in upstate New York; the City pays for agricultural conservation practices in these watersheds to protect water quality. The Cannonsville Reservoir, one of these water resources, was the focus of the NIFA CEAP study ( Osmond et al., 2012 ). Many conservation practices were funded by New York City, but the cornerstone of water quality protection was nutrient management. In the Cannonsville Reservoir watershed, nutrient management plans were rewritten every 3 yr, and color‐coded maps were generated that specified the timing and rate of dairy manure application by field. Farmers used calendars for their nutrient management record‐keeping and indicated the date and loads of manure by field in the calendar. On a yearly basis, the calendars were submitted to a peer‐review panel consisting of farmers who certified compliance ( Osmond et al., 2012 ). Certification allowed farmers to receive supplementary reimbursement that helped offset additional costs incurred in following the nutrient management plan. Nutrient management plans were used in this watershed because plans were simplified, significant financial resources were provided, and long‐term and sufficient technical assistance was available to farmers. In a poignant comment, one farmer whom the research team visited told them he would probably abandon all of his practices if subsidies ceased, even though he thought that they were valuable.

Nutrient management was widely adopted in two of the NIFA‐CEAP watersheds: Arkansas and New York. The Arkansas Lincoln Lake watershed NIFA CEAP project focused on nutrient management ( Hoag et al., 2012a ) on cattle pastures that receive litter from broiler operations. Lincoln Lake is part of the Illinois River system, and P reductions were required due to litigation between the states of Arkansas and Oklahoma. Conservation practices focused on nutrient management, exclusion fencing, and pasture management adoption ( Table 2 ). Farmer adoption was low until a dedicated extension agent was hired who gained the trust of watershed farmers. By working with a small number of farmers (<65) on a one‐to‐one basis, this agent helped producers trust soil test results, lower litter application rates, and export litter outside the watershed. Nutrient management change in this watershed required resources to hire an extension agent ( Hoag et al., 2012a , b ) and the threat from the lawsuit. Generally, nutrient management plans are written without additional outreach to farmers, so it is not surprising that in many NIFA CEAP watersheds the plans were not implemented.

The reluctance of Nebraska farmers to change N rates was confirmed through an analysis of reductions in groundwater NO 3 –N from 1986 to 2002 ( Exner et al., 2010 ). The NO 3 –N reductions of 0.26 mg L −1 yr −1 were attributed not to reduced N fertilizer rates (which were in fact level) but to increased corn yields and lower irrigation rates as a consequence of changes from furrow to sprinkler irrigation.

One NIFA CEAP study (Nebraska) focused on reducing N in the groundwater ( Meals et al., 2012b ). Due to high NO 3 –N in the aquifer, farmers were semiregulated in the area of study. They were required to test and report N content in irrigation water, animal waste, and soil to a depth of 0.9 m. Fertilizer timing and record keeping was mandated, as was education. A survey of 600 farms in the larger Central Platte Natural Resource District indicated a large number of farmers using soil testing (regular soil samples, 91%; deep soil samples, 72%), crediting legumes (75%), and testing irrigation water for NO 3 (50%). However, in our key informant survey, one farmer stated that he stopped using his moisture meters because too much management was required. Despite a high level of nutrient management practices, many farmer key informants in this project were clear that ensuring sufficient N fertilizer rates was essential ( Woods et al., 2014 ). Perceived effectiveness of the nutrient management efforts varied relative to the key informant's profession. For instance, one agency official said, “There are a lot of outreach and education programs for producers through University of Nebraska Lincoln extension, the Natural Resource Districts, and INE staff. They advertise the programs though newsletters, news media, farm magazines. I think the programs have been very effective given the high demand for participation, especially in the nutrient management and transfer irrigation systems.” However, a farmer stated the following: “… probably the least effective [conservation practices] would be the seminars explaining to farmers how they can reduce the N that they use. Even if they have facts and field data, farmers always say, well that was your field and your conditions but they hate to put too little on in case it's a really good year. They want the N [to be] there to use it. Farmers are always optimists—this is going to be a good year.” Although Bosch et al. (1995) believed that education would lead to behavior change, this did not appear to be the case.

The two most disliked conservation practices were riparian buffer installations and nutrient management ( Luloff et al., 2012 ). Riparian buffers were disliked because they removed land from production. Farmers disliked nutrient management for a variety of reasons. In one watershed with significant areas under nutrient management plans on paper, we were told farmers had abandoned these plans. As a key informant in that watershed said, “Nutrient management was a failure. Some folks cheated the system and some just wouldn't sign up. Farmers want to brag about yields and not return on investments.” Farmers often expressed the need to ensure sufficient nutrients to their crops for optimum yielding years as a guide for determining N rates (Nebraska and Kansas); conversely, farmers often did not believe the university fertilizer recommendations—particularly regarding N application—were correct (Kansas and Indiana). These farmers are not unlike those surveyed in Michigan, who rarely use university recommendations and who were concerned that reductions in fertilizer would reduce yields ( Stuart et al., 2014 ).

A key informant survey conducted in each of the 13 NIFA CEAP watersheds was especially useful in providing information about farmers’ thinking relative to conservation practice adoption and use. Of the 196 watershed key informants, 33 were farmers. Farmers understood the water quality problem in their watershed almost as well as the federal agency personnel and as well as did university, soil and water conservation district, and watershed association personnel. The decision to adopt or not to adopt conservation practices was not associated with understanding the water quality problem in their watershed; there were other more important factors ( Luloff et al., 2012 ).

North Carolina Basin and Watershed Agricultural Surveys

Surveying over 5000 agricultural fields required the workload to be spread over different years. The Tar‐Pamlico survey occurred in 2004, Jordan survey in 2006, and Neuse survey in 2009. The results presented here focus on reported N and P application rates, soil test data, and farmer nutrient management behavior, although the latter information was collected only for the Neuse River Basin and Jordan Lake watershed fields.

Agricultural areas in the Tar‐Pamlico and Neuse River Basins spanned physiographic regions in North Carolina that included the coastal plain and the piedmont. Land use maps (Fig. 2) clearly showed the difference in agricultural systems between these two regions, with the majority of croplands in the coastal plain and pasture or hayland in the piedmont. Neuse survey data indicated that approximately 36% of agricultural fields were in soybeans, 20% in pasture or hay, and the remaining land in other annual crops such as corn and cotton (Osmond and Neas, 2011); this basin is mostly in the coastal plain, but the upper portion is within the piedmont physiographic region. Conversely, 45 to 100%, depending on the county, of agricultural lands were in pasture or hay in the Jordan Lake survey, an area entirely contained in the piedmont physiographic region (Osmond and Neas, 2007). Cropping system differences were important relative to nutrient management decisions and farmer behavior.

Nitrogen requirements within a field and between fields can vary substantially from one year to another (Lory and Scharf, 2003; Mamo et al., 2003; Schmidt et al., 2007). Thus, predicting N requirements in any given year and field is difficult but necessary to reduce N losses (Sogbedji et al., 2000). In North Carolina, N management has been based on realistic yield expectations (RYE) (i.e., the best three yields over a 5‐yr time period) for each crop by soil series. Crop N rates are posted by the state Interagency Nutrient Management committee (NCINMC, 2014).

When interviewed, farmers were asked to list the current crop, fertilizer rate, and fertilizer type for each field enumerated; then, the N and P fertilizer rates were calculated. Initially, farmers did not understand that fertilizer meant applied N (usually liquid N as urea‐ammonium nitrate); they interpreted the question to mean a complete fertilizer, such as 15–15–15, or a starter fertilizer, such as diammonium phosphate. Most often, the reported corn N rates were suspect. Even after we retrained enumerators to gather all fertilizer data, including additional applications of N, the N fertilizer rates for corn often had to be sent back for further verification. The N rate data for other crops were more reliable because many of these crops have only one or no fertilizer application during the growing season. For example, soybean producers either applied no fertilizer or diammonium phosphate as a source of starter P (Osmond et al., 2006; Osmond and Neas, 2007, 2011). Obtaining accurate N fertilizer application rates, even with trained enumerators and data checks, is not easy or trivial.

To determine overapplication of N, reported N rates were compared with the RYE N rates in the NLEW tool. In the Tar‐Pamlico River Basin, N was as often underapplied as overapplied (Table 3). This was almost identical to the pattern in N fertilization observed in the Jordan Lake watershed. In almost half of these counties, the amount of applied N fertilizer was less than what the crops needed based on RYE rates, which are a function of soil mapping unit (Table 3). When applied N rates exceeded RYE‐based crop needs, the amount of excess N was generally quite small. The NLEW analysis also did not include pasture, many of which were not fertilized or were underfertilized by approximately 60% of N needs (Osmond and Neas, 2007). If nutrient management plans were implemented in the Jordan Lake watershed, applied N would increase. Overall, the data demonstrated that farmers were not matching crop N needs to N fertilizer rates regardless of whether they had a nutrient management plan; most, however, did not have plans.

Table 3. Amount of nitrogen fertilizer applied to all crop acres enumerated by county vs. the amount of nitrogen recommended by North Carolina Interagency Nutrient Management Committee for those crops by county in the Tar‐Pamlico River Basin and the Jordan Lake watershed. County N applied by farmers N needed per North Carolina nutrient recommendations kg Tar‐Pamlico River Basin Beaufort 3,925 3,990 Edgecombe 5,875 7,808 Franklin 5,334 5,985 Granville 1,687 2,752 Halifax 3,723 4,598 Hyde 20,448 7,789 Martin 4,406 3,599 Nash 4,217 4,928 Pamlico 493 240 Pitt 6,183 6,690 Washington 3,004 2,902 Wilson 2,091 3,705 Jordan Lake watershed Alamance 14,614 39,303 Caswell 1,871 1,659 Chatham 44,286 30,260 Forsyth 1,519 4,786 Guilford 50,730 125,504 Orange 49,191 48,524 Randolph 10,325 7,656 Rockingham 16,192 36,849 Wake 161 103

Soil sampling is an important tool for nutrient management decision‐making relative to P and other nutrients, such as K, calcium, and micronutrients. In the Neuse River Basin, 97% of the fields were soil tested during the past 3 yr, whereas in the Jordan Lake watershed, only 36% of the fields had been tested over the same time period. The mean range of Mehlich 3 soil test P (STP) on agricultural fields in the Neuse River Basin was 135 mg kg−1, with a minimum of 3 mg kg−1 and a maximum of 865 mg kg−1; generally, over 60 mg kg−1 no additional P is recommended (Hardy et al., 2014). Twelve counties had mean STP levels above 100 mg kg−1, reflecting very high soil test ratings, and the other five counties were high. Because dissolved‐ or sediment‐attached P losses increase as STP increases, lowering STP is important for reducing nutrient losses from cropland (Sharpley, 1980). Applied P was similar for fields in the Neuse Basin regardless of P needs (37 kg P ha−1 for soils that did not need P and 39 kg P ha−1 for fields that did). In the Tar‐Pamlico River Basin, average STP levels were very high in seven counties, high in four counties, and medium in one county. Over 67% of the fields did not need P applications, yet P application rates were identical (29 kg P ha−1) regardless of whether the soil needed P or not. Finally, in the Jordan Lake watershed, 65% of the agricultural fields had STP levels in the medium or low category; the majority of agricultural land use was pasture based, and farmers reduced costs by minimizing fertilizer application. The average added P to fields in the Jordan Lake watershed was 79 kg P ha−1 for soils testing high or very high but only 27 kg P ha−1 for soils testing low or medium. This discrepancy in P fertilizer application reflected extant cropping systems: low P fertilization of pastures and high P rates for tobacco. Large quantities of P were still being applied to tobacco.

In one county in the Neuse River Basin, an extension agent worked with farmers on nutrient management plans, which enabled the farmers to write their own nutrient management plans. This effort was based on the belief that if farmers had more ownership in the content of the plans they would use them. Nutrient management plans were written for over 16,000 ha. In addition, farmers were required to attend a 1‐d nutrient management training session conducted by North Carolina Cooperative Extension county agents (NCDENR, 2014c), and over 2000 farmers attended. Despite these efforts, the agent reported that none of the farmers was using the plans 2 yr after plan writing and nutrient management training (R. Pleasants, personal communication, 2006).

Using fertilization rates and crop information, we determined if an individual farmer was changing fertilizer rates on different fields for the same crop. In the Neuse River Basin, farmers with multiple fields of the same crop did not vary their fertilization between fields on cotton (92%), corn (73%), flue‐cured tobacco (86%), pasture/hay (73%), soybeans (90%), wheat (82%), or miscellaneous crops (81%). In some cases, such as soybeans, fields fertilized identically received no fertilizer; the effective fertilizer application rate was 0 on approximately 50% of the soybean fields (Osmond and Neas, 2011). Similar results were obtained in the Tar‐Pamlico basin (Osmond et al., 2006). In the Jordan Lake watershed, 120 producers with multiple fields of the same crop always used the same fertilizer regime, whereas 9 (7%) farmers changed fertilization rates for the same crop depending on the field (Osmond et al., 2013).

Fertilizer decision‐making was an essential component of nutrient management regardless of the existence of plans. Fertilizer decisions when no nutrient management plans were available were made by the farmers (60% Neuse and 70% Jordan; Table 4) (Osmond and Neas, 2007, 2011). Twenty percent of the farmers in the Neuse relied on fertilizer dealers to make these decisions, whereas only 10% did so in the Jordan Lake watershed. When no plans were available, the role of extension, NRCS, and paid consultants relative to fertilizer recommendation was low (<5%).

Table 4. Organization or individual who makes fertilizer decisions on agricultural fields for farmers in the Neuse River Basin or Jordan Lake watershed when no nutrient management plan is used. Organization or individual Neuse River Jordan Lake No.of people % No. of people % Fertilizer dealer 391 19.7 15 8.5 Paid consultant 51 2.6 0 0 NRCS 5 0.3 5 2.9 Extension 10 0.5 2 1.1 Friend/other farmer 15 0.8 5 2.9 Self 1192 60.0 123 70.3 Other 239 12.3 7 4.0 No commercial fertilizer applied 81 4.1 18 10.3

Application of nutrients, although not identical to fertilizer decision‐making, followed the same pattern. In Neuse, 50% of the fertilizer was applied by farmers and 36% by fertilizer dealers, whereas in Jordan, farmers applied 69% of the fertilizer and dealers applied 17%. Although N rates did not appear excessive in the regulated basins, many farmers had over a 30‐yr supply of P in their soils (Kamprath, 1999). Despite this, P fertilizer additions continued without regard for soils test recommendations or university research that demonstrated even starter P was unnecessary on these soils (Cahill et al., 2013).

Together, these data demonstrated that producers were making many of their fertilization decisions without technical advice and that most were not following nutrient management plans that would prescribe different fertilizer rates based on soil test results and RYE. The Neuse River Basin survey analysis indicated that nutrient management was not occurring. Due to the high or very high STP, farmers could have discontinued their use of P fertilizer in many fields, particularly in the coastal plain where STP levels were usually high or very high (Cahill et al., 2013). Nitrogen did not appear to be excessively applied in either physiographic region, but for different reasons. In the coastal plain, mixed cropping systems, which included corn, soybeans, tobacco, cotton, sorghum, and a variety of vegetable crops, predominated. Soybeans had little N applied, and cotton and tobacco used lower levels of N to minimize excess vegetative growth at the end of the season (McCants and Woltz, 1967). The piedmont area was predominantly pasture and hay used for were cow/calf operations. Most of the pastures were underfertilized with N by as much as 60% because the farmers could not afford more N fertilizer. Regardless, whether farmers were applying N or P, fertilizer decision‐making did not appear to be based on soil test recommendations, state‐approved RYEs, or nutrient management plans.