Managing Soil Phosphorous Accumulation From Poultry Litter Application Through Vegetable/Legume Rotations

Final Report for LS95-069

Project Type: Research and Education
Funds awarded in 1995: $135,000.00
Projected End Date: 12/31/1998
Matching Non-Federal Funds: $90,813.00
Region: Southern
State: Texas
Principal Investigator:
D. R. Earhart
Texas Agricultural Experiment Station
Expand All

Project Information

Abstract:

Applying poultry litter at rates sufficient to meet crop needs for N results in accumulation that can lead to non-point source pollution of surface waters. Legumes are able to use significant amounts of P. An advantage of using legumes for removing excess P is that no additional N fertilizer has to be applied since legumes can obtain N from the atmosphere through N2 fixation. Factored experiments were established at the Texas A&M University Research and Extension Center at Overton (Spring 1995) and Oklahoma State University Vegetable Research Station at Bixby (Fall 1995). The objectives were (1) investigate the use of warm- and cool-season legumes in rotational cropping systems to remove excess P supplied by poultry litter (Texas-Oklahoma); (2) evaluate cool-season legumes for P uptake efficiency following litter application rates on spring vegetables (Texas); (3) monitor P accumulation and run-off in a vegetable-forage legume rotation system (Texas); (4) demonstrate use of annual legumes in cropping systems, utilizing poultry litter as a nutrient source on grower-owned land under grower conditions (Texas-Oklahoma).

Litter rates for all objectives were based on soil test nitrogen (N) requirement of the vegetable crop and percent N content of the litter. Litter was applied to the vegetable crop only. Treatments were incorporated immediately after application by power tilling.

Cumulative 1X litter rates over the study period were:

  • Objective 1. Spring-11.3 tons/ac, fall-5.9 tons/ac;

    Objective 2. 13.6 tons/ac;

    Objective 3. Spring-6.8 tons/ac, fall-5.9 tons/ac;

    Objective 4. 4.0 tons/ac.

In objective 1 (Texas) the vegetable crops were: watermelons – spring 1995; broccoli – fall 1995; tomato – spring 1996; collards – fall 1996; squash – spring 1997; turnips – fall 1997. The spring legume crop was ‘Iron and Clay’ cowpeas and the fall crop was crimson clover. In Oklahoma the vegetable crops were: fall – broccoli, turnip, spinach: spring – sweet corn, muskmelon. The fall cover crop was hairy vetch and the spring crop was southern cowpea.

Dry matter yields of Iron and Clay cowpeas and crimson clover were not significantly affected by fertilizer treatment during the three year study period (1995-97).

Mean percent P increased over time for both legumes as rate increased (Iron and Clay cowpeas: control – .34%, 1X – .44%, 2X – .47%, 4X – .52%, commercial blend – .40%; crimson clover: control – .34%, 1X – .42%, 2X – .49%, 4X – .62%, commercial blend – .43%). Pounds per acre of P removed by both legumes also increased as rate increased (Iron and Clay cowpeas: control – 7.0 lbs, 1X – 9.0 lbs, 2X – 9.3 lbs, 4X – 11.4 lbs, commercial blend – 8.0 lbs. Crimson clover: control – 7.7 lbs, 1X-12.9 lbs, 2X – 13.2 lbs, 4X – 16.5 lbs, commercial blend – 11.3 lbs).

Average P accumulation in the 0-6 in. soil level over six seasons was less at the 1X (57 ppm) level of application than the 2X (112 ppm) and 4X (195 ppm). Phosphorus levels for the commercial blend (23 ppm) were equal to the control (21 ppm).

Utilizing a cropping system approach to reduce soil P accumulation proved to be effective. Mean data indicated that a system of spring vegetable-fall legume reduced P concentrations in the surface 0-6 in. of soil significantly to 48 ppm. Greater concentrations were found with systems of fall legume-spring vegetable (90 ppm) and spring vegetable- fall vegetable (96 ppm).

In Oklahoma under a cool-season vegetable rotation, cowpeas effectively lowered soil N levels but not soil P levels. In a warm-season vegetable rotation, hairy vetch appeared to raise soil N levels, but showed some evidence of controlling soil P levels. There was no buildup of soil P after two litter applications, even at the 2X rate.

In objective 2 the crops were: watermelon – 1995; sweet corn – 1996; tomato – 1997. In fall 1995, cool-season legumes consisting of crimson clover, berseem clover, hairy vetch, and red clover were seeded. Due to loss of stand of berseem clover because of freezing weather, a crimson clover-ryegrass mix was substituted in the 1996 planting.

Poultry litter rate showed no significant effect on mean dry matter yield of the four legumes. There was a significant effect by legume species on mean dry matter yield over time. Crimson clover-ryegrass mix produced 3,066 lbs/acre followed by hairy vetch with 2,012 lbs/acre. Crimson clover produced 1,361 lbs/acre and red clover 832 lbs/acre.

Mean plant P concentration in the 0-6 in soil depth increased as litter rate increased (control – .49%, 1X – .54%, 2X – .60%, 4X – .70%, commercial blend – .50%). Phosphorus uptake also increased as rate increased (control – 5.8 lbs/ac, 1X – 7.4 lbs/ac, 2X – 7.9 lbs/ac, 4X – 11.4 lbs/ac, commercial blend – 6.8 lbs/ac). Hairy vetch contained a mean percent plant P of .63% followed by crimson clover (.57%), crimson clover-ryegrass (.54%) and red clover (.48%). Phosphorus removal was greatest with a crimson clover-ryegrass mix (12.9 lbs/ac) followed by hairy vetch (10.2 lbs/ac), crimson
clover (7.8 lbs/ac) and red clover (4.2 lbs/ac). Mean concentration of P in the 0-6 in. soil depth was reduced over time by hairy vetch to 77 ppm, followed by crimson clover (87 ppm), crimson clover-ryegrass (95 ppm) and red clover (103 ppm).

In objective 3 the vegetable crops were: turnip – fall 1995; sweet corn – spring 1996; turnip – fall 1996; watermelon – spring 1997. The cover crops were crimson clover and Iron and Clay cowpeas.

Due to a lengthy dry spell, there was not enough precipitation to collect run-off in either fall 1995 or spring 1996. In fall 1996 two major rainfall events occurred. Concentrations of P in the runoff were very low (< 0.8 ppm). No differences were found regardless of poultry litter rate or cropping system. This could be attributed to soil incorporation of the treatments. Mean P accumulation in the 0-6 in. soil depth increased from 70 ppm to 185 ppm when litter rate was increased from 1X to 4X. Phosphorus levels from the commercial blend remained close to that of the control (17.5 ppm and 27.0 ppm respectively). The least amount of residual P in the surface 0-6 in. soil depth was from a system of spring vegetable-fall legume (57 ppm) followed by spring vegetable-fall fallow (76 ppm) and spring legume-fall vegetable (92 ppm). Objective 4 was implemented in spring 1996 with the establishment of two demonstration plots. Litter at the rate of 4 tons/ac was applied. Tomato plants grown on plots with litter produced an average of 28 lbs of fruit per plant. Yield was not obtained for sweet corn but was reported that more ears were harvested from the poultry litter plots than the commercial fertilizer plots. The plot area that received litter produced 1,356 lbs/ac more vetch than that receiving commercial fertilizer. Results have identified strategies that reduce non-point source pollution and soil imbalances and offer an opportunity for adoption of improved, environmentally sound management practices. Due to demonstrations of litter use in vegetable production programs, grower interest and awareness of the nutrient value of poultry litter has been increased. Continued demonstrations will help show growers how a cropping system approach can be used to alleviate problems associated with litter use, especially P accumulation. Also, through outreach programs, we will continue to educate growers on nutrient management strategies through environmentally sound best management practices.

Project Objectives:

The objectives of this research are based on a study funded by the Southern Region SARE/ACE Program ending 1 Feb. 1995. This funded study was designed to: 1.) Investigate the feasibility of growing cool- and warm-season forage grasses in rotational vegetable cropping systems to reduce NO3-N accumulation, leaching, and run-off from poultry litter applications; 2.) Evaluate litter rate and time of application on vegetables.

The current objectives are: 1.) Investigate the use of warm- and cool-season annual forage legumes in rotational cropping vegetable systems to remove excess P supplied by poultry litter; 2.) Evaluate cool-season legume species for P uptake efficiency following litter application rates on spring vegetables; 3.) Determine P uptake efficiency and monitor P run-off in a vegetable forage-legume rotation system; 4.) Demonstrate the use of annual legumes in vegetable cropping systems, utilizing poultry litter as a nutrient source, on grower-owned land under grower conditions.

Introduction:

Several southern states are experiencing a rapid growth in the poultry industry (9, 11). Expanded production increases the amount of poultry litter requiring disposal in a timely, profitable, and environmentally sound manner. Most mineral elements essential for plant growth are found in poultry litter (23,38). Recent studies suggest that poultry litter is an excellent nutrient source for vegetable production (1, 11, 13, 15, 27, 29). Application of 22.4 t·ha-1 of 30% moisture poultry litter can supply approximately 645 kg N, 227 kg P, 342 kg K, 127 kg Ca and 28 kg Mg, with trace amounts of Fe, Mn, Zn, B and Mo (21). Nitrogen (N) – phosphorus (P) – potassium (K) ratio in poultry litter does not match the ratio of nutrients required by vegetable crops. As a result, complete nutrient utilization is rarely accomplished. Present recommended application rates are based on N content of the poultry litter and N recommendation for specific crop production (17, 41). Continuous applications to crop land, based on this practice, have resulted in accumulation and leaching of soil NO3-N into ground water supplies (5, 10, 44). When litter is applied to meet the N needed, P and K can accumulate and result in conditions detrimental to plant growth and increase the risk of non-point source pollution of surface water (32). Phosphorus additions to surface waters from non-point agricultural sources is an increasing resource management concern. Movement of P to surface waters can accelerate eutrophication (6, 7, 37). Phosphorus has been regarded as the primary nutrient controlling biological activity in surface waters (28). Excess soil P can inhibit uptake of metallic trace elements such as Fe, Zn, and Cu (40). Excessive soil K can cause soil salinity which is detrimental to seedlings, crop growth, and reduces yields, as well as lowers availability of Mg (38).

Cooperative studies in Texas and Oklahoma conducted over a three-year period (1992-94) using poultry litter as a fertilizer source, indicate that increased movement of NO3-N through the soil profile can be reduced by incorporating warm- and cool-season annual forage grasses as cover crops in vegetable cropping systems (12, 14). However, available soil P content of the soil continued to increase in the surface 0.3 m from a low of 39 to a high of 500 kg/ha. This increase is approaching the maximum loading rate of 672 kg/ha (300 ug/g) set by Soil Conservation Standards for typical soil types for the East Texas area and major vegetable production areas of Oklahoma (sandy, sandy loam, loamy sand) (42). Studies in other states have shown that long-term or excessive litter applications to crop land has caused excessive accumulation of extractable P (3, 16, 26, 37, 45). Soil tests have shown that 71% of soils to be planted to horticultural crops had P levels greater than 65 kg/ha compared with 51% for agronomic crops (43). Phosphorus fertilizer recommendations and sufficiency levels will tend to be higher for vegetables than for field crops (33). It has been suggested that more emphasis should be given to soil P and its management (22).

Legumes are soil building crops. Their ability to fix atmospheric N and the beneficial effects on soil structure and reduction of soil erosion are well known. Legumes have the ability to deplete soil P and K levels (19). Red clover removed as much as 44 kg P and 336 kg K/ha (34). In the first four years of a 7-year study, it was found that legume hay removed 54% of applied P and over 100% of K (24). On the average, legumes contain 1.74 times as much P as grasses (8). Phosphorus was found to be lower under legumes than grasses in the 0 to 0.15 m soil depth (46). Winter legumes lowered soil pH and extractable P in the 0 to 0.075 m depth and redistributed K to the surface (20). Adaptation requirements of legume species differ considerably (2). The realized value of a cover crop to a particular system will depend on the selection and management of species, and interaction with the rest of the cropping system (35).

Management is the key to efficient utilization of litter nutrients by a crop. Proper management will increase economic returns, sustain soil productivity, and reduce environmental concerns. Cover crops can be used to recycle nutrients or remove excess nutrients through grazing, hay or silage.

Data on the efficiency of annual legumes for removing nutrients supplied by poultry litter are limited. Cropping studies utilizing legumes in southern row crop farming systems need to be conducted in two major temperate zones, A and B. These zones cover an area from eastern Texas and Oklahoma to the Atlantic Coast.

Regulatory agencies are now beginning to address non-point source pollutants such as P. Producers are concerned that these agencies will begin to make policy without sound, scientific data from which to base their decision. Data are needed to address nutrient management, particularly P, for water quality protection in order that future policy will be grower friendly (30).

Cooperators

Click linked name(s) to expand
  • M. L. Baker
  • V. A. Haby
  • Brian A. Kahn

Research

Materials and methods:

Factored experiments designed to evaluate the objectives were established at the Texas A&M University Agricultural Research and Extension Center, Overton, beginning in spring 1995. Similar designs were established at the Oklahoma State University Vegetable Research Station, Bixby, beginning in fall 1995. The plot areas on which the experiments were established in both states were used in cooperative studies conducted over a three-year period (1992-94) in which movement of NO3-N was studied. Soil sub-samples were obtained at random 15 cm (6 in) depths from previous plots that had received poultry litter applications of 0, 1X, 2X, and 4X recommended rate as well as commercial fertilizer blend. The samples were analyzed by the Texas A&M University Soil Testing Lab and Oklahoma State Soil Testing Lab for fertilizer recommendations.

Poultry litter was obtained and analyzed for total N. Litter was applied according to percent N, moisture content, and recommendation for maximum vegetable crop yield based on N. This was considered the 1X rate. Commercial fertilizer rates were based on recommendations for N-P-K. All treatments were incorporated using a power tiller. For determining P movement and concentration during the study, samples were obtained in 0-15, 15-30, and 30-45 cm (0-6, 6-12, and 12-18 in.) increments. Plant and soil samples were dried and prepared for chemical analysis by standard laboratory procedures.

The warm-season legume used in objectives 1 and 3 was cowpea (‘Iron and Clay’). Cool-season legumes used in some of all objectives were crimson clover (‘Dixie’), hairy vetch, red clover (‘Cherokee’), and berseem clover (‘Bigbee’). The berseem clover stand was lost to freezing temperatures in 1995. It was replaced with a crimson clover-ryegrass mix in 1996. The cool-season grass used was ryegrass (‘TAM 90’).

OBJECTIVE 1: Rotational Cropping System.

Location: TAES-Overton, OSU-Bixby.

TAES: Spring 1995

Experimental randomized plots were established at the Texas A&M University Agricultural Research and Extension Center at Overton. The purpose was to investigate the feasibility of growing warm- and cool-season legume crops to remove excess P supplied by poultry litter and commercial blend fertilizer in rotational cropping vegetable systems.

Fifteen treatments were evaluated in a split-plot design with 3 replications. The whole plot was cropping system (spring legume-fall vegetable, spring vegetable-fall legume, spring vegetable-fall vegetable) with litter rate (0, 1X, 2X, 4X, and commercial blend) as sub-plots. The whole plot dimension was 9.7 m (32 ft) by 16.2 m (53.32 ft). Individual sub-plots were 4.8 m (16 ft) by 4.1 m (13.33 ft). Plot ends were separated by 0.9 m (3 ft) alleys.

On 27 April, poultry litter containing 3.4% N and 57.2% dry matter was hand applied to plots in cropping systems of spring vegetables-fall legumes and spring vegetables-fall vegetables. The 1X rate was 2.2 t/ha (1.0 ton/A). A commercial fertilizer blend of 48.8N-12.2P-28K kg/ha (40N-10.9P-25K lbs/A) was applied as a check. All plots were incorporated by power tilling.

Watermelon transplants (‘Fiesta’) were hand planted on 28 April. The spring legume-fall vegetable plots were drilled to cowpeas on 5 May. Watermelons were harvested on 19 July and cowpea plots on 16 Aug. Soil samples were obtained on 9 September.

TAES: Fall 1995

On 28 Sept., litter containing 3.4% N and 51% dry matter was hand applied to plots in cropping systems of spring legumes-fall vegetables and spring vegetables-fall vegetables. The 1X rate was 8.3 t/ha (3.7 tons/A). A commercial fertilizer blend of 89.6N-24.4P-28K kg/ha (80N-21.8P-25K lbs/A) was applied on the same date. An additional 56N kg/ha (50N lbs/A) was applied on 2 Nov. as a sidedress application.

The spring vegetable-fall legume plots were drilled to crimson clover on 4 Oct. Broccoli (‘Bacchus’) was hand transplanted on 9 Oct. Broccoli was harvested on 7 and 14 Nov. and clover on 2 April 1996. Soil samples from the broccoli plots were obtained on 4 Jan. and legume plots on 4 April 1996.

TAES: Spring 1996

On 26 April, litter containing 3.3% N and 60% dry matter was hand applied to plots in cropping systems of spring vegetables-fall legumes and spring vegetables-fall vegetables. The 1X rate was 6.7 t/ha (3.0 tons/A). A commercial fertilizer blend of 67.3N-17.1P-78.5K kg/ha (60N-15.3P-70K lbs/A) was applied on the same date with a sidedress application of 33.6N kg/ha (30N lbs/A) on 17 June.

The spring legume-fall vegetable plots were drill planted to cowpeas on 6 May. Tomatoes (‘Summer Flavor 5000’) were hand transplanted to the spring vegetable-fall legume and spring vegetable-fall vegetable plots on 7 May. Yield data on tomatoes were obtained on 11, 22, 26, and 30 July. Cowpeas were harvested on 13 July. Soil samples for the tomato and cowpea plots were obtained on 6 and 15 Aug.

TAES: Fall 1996

On 25 Sept., litter containing 3.3% N and 60% dry matter was applied to spring vegetable-fall vegetable plots at a rate of 8.9 t/ha (4.0 tons/A) and spring legume-fall vegetable plots at 10.0 t/ha (4.5 tons/A). for the 1X rate. A commercial blend fertilizer of 184.9N-19.5P-93K kg/ha (165N-17.4P-83K lbs/A) and 190.5-24.4P-111.6K kg/ha (170N-21.8P-99.6K lbs/A) was applied on the same date to the above respective systems.

The spring vegetable-fall legume plots were drill planted to crimson clover on 3 Oct. and collards (‘Champion’) were seeded on the remaining plots on 1 Oct. No yield data were obtained on collards due to loss of plants from sudden extremely cold temperatures. Crimson clover plots were harvested on 11 March 1997. Soil samples for all plots were obtained on 9 April.

TAES: Spring 1997

On 14 May, litter containing 3.4% N and 61% dry matter was hand applied to spring vegetable-fall legume and spring vegetable-fall vegetable plots at 3.8 t/ha (1.7 tons/A) for the 1X rate. Also on this date a commercial blend fertilizer containing 44.8N-22P-51.1K, 168 KMgSO4, 16 S kg/ha (40N-19.6P-45.6K, 150 KMgSO4, 15 S lbs/A) was applied. A sidedress application of 33.6N kg/ha (30N lbs/A) was made at bloom to the spring vegetable-fall legume plot. A blend of 44.8N-14.6P-37.2K, 168 KMgSO4, 16.8 S kg/ha (40N-13P-33.2K, 150 KMgSO4, 15 S lbs/A) with a sidedress application of 33.6 kg/ha (30N lbs/A) at bloom was applied to the spring vegetable-fall vegetable plots.

Yellow squash (‘Meigs’) was hand seeded in hills on 20 May. Yield data were obtained on 24,27 June and 3,8, 10, 14 July. Cowpeas were harvested on 18 July. Soil samples of all plots were obtained on 5 August.

TAES: Fall 1997

On 14 Oct., litter containing 3.7% N and 69% dry matter was applied at a rate of 4.2 and 2.4 t/ha (1.9 and 1.1 tons/A) as the 1X rate. On 6 Oct., a commercial fertilizer blend containing 44.8N-31.7P-74.4K, 168.2KMgSO4, 16.8 S kg/ha (40N-28.3P-66.4K, 159KMgSO4, 15 S lbs/A) and agricultural grade lime was applied at 3.36 t/ha (1.5 tons/A) to the spring legume-fall vegetable plots. An additional 44.8N kg/ha (40N lbs/A) was applied on Nov. 4. On the same date 61.6N-7.3P-60.4K, 16.8 S kg/ha (55N-6.5P-53.9K, 15 S lbs/A) was applied to the spring vegetable-fall vegetable plots. An additional application of 44.8N kg/ha (40N lbs/A) was made.

The spring vegetable-fall legume plots were drill planted to crimson clover on 17 Oct. Turnips (‘White Lady’) were seeded on 15 Oct. Turnip yield data and sub-samples were obtained on 16 Dec. 1997. Clover was harvested and sub-samples obtained on 14 April 1998. Soil samples were obtained on 7 May.

OSU: See attachment-Oklahoma Report.

OBJECTIVE 2: Evaluation For P Uptake Efficiency.

TAES: Spring 1995

Randomized plots were established in Spring 1995 at the Texas A&M University Agricultural Research and Extension Center at Overton. The purpose of this study was to evaluate cool-season legume species for P uptake efficiency following litter application rates on spring vegetables.

Twenty treatments were evaluated in a split-plot design with 3 replications. The whole plot was litter rate (0, 1X, 2X, 4X, and commercial blend). Cool-season legumes consisting of crimson clover, berseem clover, hairy vetch, and red clover were the sub-plots. The whole plot dimension was 20 m (66.65 ft) by 4.8 m (16 ft). Individual sub-plots were 20 m (66.5 ft) by 2.4 m (8 ft). Plots were separated by 0.9 m (3 ft). alleys.

On 26 April, litter containing 3.4% N and 57.2% dry matter was hand applied to plots. The 1X rate was 2.2 t/ha (1.0 ton/A). A commercial fertilizer blend of 22.4N-0P-32.5K kg/ha (20N-0P-29K lbs/A) was applied on the same date. A sidedress application of 22.4N kg/ha (20N lbs/A) was made on 6 June.

Watermelon transplants (`Fiesta’) were hand transplanted on 28 April. Plots were harvested on 18 July. Soil samples were obtained at depths previously mentioned following crop harvest.

TAES: Fall 1995

No fertilizer treatments were applied to plots in the fall. The previous mentioned legume species were strip drill planted on 4 Oct. The legume species used and rate per acre were: crimson clover, 9.1 kg/ha (20 lbs/A); berseem clover, 9.1 kg/ha (20 lbs/A); hairy vetch, 13.6 kg/ha (30 lbs/A); red clover, 5.9 kg/ha (13 lbs/A).

Plots were harvested on 2 April 1996 and soil samples obtained on 4 April.

TAES: Spring 1996

On 3 May, litter containing 3.3% N and 60% dry matter was hand applied to plots. The 1X rate was 6.7 t/ha (3.0 tons/A). A commercial fertilizer blend of 67.3N-17.1P-79K kg/ha (60N-15.3P-70.5K lbs/A) was applied on the same date. An additional 33.6N kg/ha (30N lbs/A) was applied on 12 June as a sidedress application.

Sweet corn (‘Merit’) was seeded on 8 May. Plots were harvested on 12 July. Soil samples were obtained on 29 July.

TAES: Fall 1996

No fertilizer treatments were applied to plots in the fall. Plots were planted with the same legume species except a legume-grass mix of crimson clover-ryegrass was substituted for berseem clover in Fall 1995. Plots were harvested on 11 March 1997. Soil samples were obtained on 2 April.

TAES: Spring 1997

On 14 May, litter containing 3.4% N and 61% dry matter was hand applied to plots. The 1X rate was 4.7 t/ha (2.1 tons/A). A commercial fertilizer blend of 67.3N-4.8P-102.3K, 168 KMgSO4, 16.8 S kg/ha (60N-4.3P-91.3K, 150 KMgSO4, 15 S lbs/A). An additional 33.6 kg/ha (30N lbs/A) was applied on 26 June.

Tomato plants (‘Summer Flavor 5000’) were hand transplanted on 20 May. Plots were harvested on 31 July, and 4, 6, 11, 13, 18 August. Soil samples were obtained on 3 September.

TAES: Fall 1997

No fertilizer treatments were applied to the plots in the fall. The plots were strip drilled to crimson clover, crimson clover-ryegrass, hairy vetch, and red clover on 17 Oct. Plots were harvested on 15 April. Soil samples were obtained on 12 May.

OBJECTIVE 3: Accumulation and Runoff.

TAES: Fall 1995

Experimental randomized plots were established in Fall 1995 at the Texas A&M University Agricultural Research and Extension Center at Overton. The purpose was to determine P uptake efficiency and monitor accumulation and run-off in a vegetable-forage legume rotation system.

Twelve treatments were evaluated in a split-plot design with two replications. The whole plot was cropping system (spring vegetable-fall legume; spring legume-fall vegetable; spring vegetable-fall fallow). The sub-plots were fertility treatment (0, 1X, 4X, commercial blend fertilizer). The whole plot dimensions were 16.2 m (53.32 ft) by 15.2 m (50 ft). Individual sub-plots were 15.2 m (50 ft) by 4.0 m (13.33 ft). Graded troughs lined with 6-ml black plastic were established at the ends of the individual sub-plots and connected to Parshall flumes with throat widths of 7.6 cm (3.0 in). Containers were installed at the end of each flume to intercept a portion of the run-off to determine P loss. Samples were collected after every major rainfall event and immediately frozen in order to stabilize nutrients until preparation for chemical analysis. Phosphorus accumulation was determined by soil sampling at previously described increments.

On 29 Sept., litter containing 3.4% N and 51% dry matter was hand applied to plots. The 1X rate for the spring legume-fall vegetable plot was 3.1 t/ha (1.4 tons/A) and for the spring vegetable-fall fallow 2.5 t/ha (1.1 tons/A). A commercial fertilizer blend of 22.4N-4.9P-32.5K kg/ha (20N-4.4P-29K lbs/A) and 44.8N-12.2P-27.9K kg/ha (40N-10.9P-24.9K lbs/A) was applied on the same day to the above mentioned plots respectively. The spring vegetable-fall legume plot did not receive a fertilizer treatment.

Turnips (‘Purple Top’) and crimson clover were seeded on 29 Sept. to their respective plots. Turnips were harvested on 3 Jan. and clover on 2 April 1996. Soil samples were obtained on 29 March.

TAES: Spring 1996

On 3 May, litter containing 3.3% N and 60% dry matter was hand applied to plots. The 1X rate for both the spring vegetable-fall legume and spring vegetable-fall fallow plots was 6.7 t/ha (3.0 tons/A). A commercial fertilizer blend of 13.4N-12.2P-32.5K kg/ha (12N-10.9P-29K lbs/A) and 123.3N-2.4P-18.6K kg/ha (110N-2.2P-16.6K lbs/A) was applied on the same day to the above mentioned plots respectively. The spring legume-fall vegetable plot did not receive a fertilizer treatment.

Sweet corn (‘Merit’) and Iron and Clay cowpeas were seeded on 8 May 1996 to their respective plots. Sweet corn was harvested on 16 July and cowpeas on 13 Aug. Soil samples were obtained on 15 August.

TAES: Fall 1996

On 27 Sept., litter containing 3.3% N and 60% dry matter was hand applied to plots. The 1X rate for the spring legume-fall vegetable plot was 10.1 t/ha (4.5 tons/A) and for the spring vegetable-fall fallow 3.3 t/ha (1.5 tons/A). A commercial fertilizer blend of 190.5N-56P-134.5K kg/ha (170N-50P-120K lbs/A) and 100.8N-17.1P-79K kg/ha (90N-15.3P-70.5K lbs/A) was applied on the same day to the above mentioned plots, respectively. The spring vegetable-fall legume crop did not receive a fertilizer treatment.

Turnips (‘White Lady’) were seeded on 1 Oct. and crimson clover was drilled on 3 Oct. Turnip plots were harvested on 26 Nov. Clover yield data was obtained on 8 April 1997. Soil samples were obtained on 10 April.

TAES: Spring 1997

On 14 May, litter containing 3.4% N and 61% dry matter was hand applied to spring vegetable-fall legume and spring vegetable-fall fallow plots. The 1X rate for both systems was 2.1 t/ha (0.9 tons/A). A commercial blend of 22.4N-12.2P-27.9K, 16.8 S and 22.4N-12.2P-27.9K, 16.8 S kg/ha (20N-10.9P-24.9K, 15 S and 20N-4.4P-8.3K, 15 S lbs/A) was applied to the above mentioned plots respectively on the same date.

Watermelon (‘Allsweet’) transplants were hand planted on 20 May. Iron and Clay cowpeas were drill seeded on 11 June. Yield data on watermelon were not obtained due to severe animal damage. Cowpeas were harvested on 18 July. Soil samples were obtained on 9 September.

OBJECTIVE 4: Demonstrations.

Locations: Texas – Oklahoma

TEXAS:

Demonstration plots were established in Texas in the spring and fall of 1996. A plot area consisting of 0.2 ha (0.50 acres) was established on the Rollie Skinner farm at Alto, Texas in Cherokee Co. Agricultural-grade lime was applied on 13 March at the rate of 2.2 t/ha (1 ton/A). On 15 March, one-half of the plot received 8.9 t/ha (4 tons/A) of litter containing 3.5 % N. The other half received a commercial blend fertilizer of 128.9N-34.2P-37.2K kg/ha (115N-30.5P-33.2K lbs/A).

On 22 March, the plots were seeded to sweet corn (‘Merit’). The plots were harvested in July. Soil samples were obtained 16 August for residual P determination.

The plot area was seeded with hairy vetch in Oct. Plots were harvested, sub-samples taken and soil samples obtained on 9 April.

OKLAHOMA: See attachment-Oklahoma Report.

Research results and discussion:

The study was completed on schedule. The final treatments were applied in the fall 1997 and all project objectives were met in a timely fashion. No major problems have been encountered in carrying out this project in respect to Texas A&M or Southern SARE.

OBJECTIVE 1: Rotational Cropping System.

Location: TAES-Overton, OSU-Bixby

TAES:

Dry matter yield of Iron and Clay cowpeas and crimson clover were not affected by fertility treatment during the three years studied (Tables 1, 2). Plant P concentration of both legumes showed a highly significant linear increase as rate increased. A significant increase in P uptake was found in 1995 and 1997.

Application rates of poultry litter affected soil P over time (Fig. 1). Applying litter at the recommended rate from soil testing (1X), maintained P levels in the surface 0-15 cm (0-6 in) depth at approximately 60 mg/kg (ppm) during the study period of 5 seasons. Leaching of P through the soil profile was also reduced. Increasing litter application rate from 2 times (2X) to four times (4x) the recommended, increased concentration. The least amount of P accumulation was from commercial blend fertilizer and was maintained at approximately the same level as that of the control plot.

Mean residual soil P over time increased dramatically as rate increased (Fig. 2). Mean accumulation was less (57 ppm) at the 1X level of application than the 2X (112 ppm) and 4X (195 ppm) rate. Levels for the commercial blend (23 ppm) were equivalent to the control (21 ppm). Data from an extra plot, to which commercial fertilizer was applied according to soil test P recommendation, showed equivalent levels of P when compared to the 1X rate.

Utilizing a cropping system approach to reducing soil P accumulation and leaching proved to be effective (Fig. 3). Mean data collected over 6 seasons indicated that a system of planting a spring vegetable and following with a fall legume reduced P concentrations in the surface 0-15 cm (0-6 in) of soil significantly (48 ppm) (Fig. 4). Greater concentrations were found with systems of fall legume-spring vegetable (90 ppm) and spring vegetable-fall vegetable (96 ppm).

OSU: See attachment-Oklahoma Report.

OBJECTIVE 2: Evaluation For P Uptake.

TAES:

Dry matter yield of four legumes and a legume-grass mix showed a slight quadratic response in fall 1995 (Table 3). The 4X litter rate tended to decrease yield. There was no significant effect due to litter rate in 1996 or 1997. Plant P concentrations increased linear in 1995 and 1996 but tended to decrease at the 4X rate in 1997.

A significant difference in dry matter yield, plant P concentration and P uptake was found to be due to cover crop in all three years. Hairy vetch produced the highest yield in 1995 but showed equal production in 1996 with a crimson clover-ryegrass mix. The mix was highest in 1997. Hairy vetch contained a significantly greater concentration of P in all three years. The greatest amount of P uptake was with hairy vetch in 1995 and 1996. In 1997 a crimson clover-ryegrass mix showed the highest P uptake.

Phosphorus levels in the soil were maintained or reduced by fall legume cover cropping (Fig. 5). This was most pronounced at the 4X rate. The greatest mean residual soil P over time was from the 4X rate (Fig. 6). Phosphorus concentration increased as rate increased from 1X to 2X but was not as dramatic a the 4X rate. Commercial blend treatments were equal to the control. In 1995, removal of P from the 0-15 cm (0-6 in) depth was greatest with crimson clover and hairy vetch (Fig. 7). Hairy vetch removed more P in 1996, while in 1997 crimson clover and hairy vetch demonstrated the greatest removal. The mean effect of legumes on residual soil P over time showed that hairy vetch was most efficient, followed by crimson clove and crimson clover-ryegrass mix (Fig. 8). The least efficient was red clover.

OBJECTIVE 3: Accumulation and Run-off.

TAES:

Due to a lengthy dry spell, there was not enough precipitation to collect any run-off or leachate in either fall 1995 or spring 1996. In fall 1996 two major rainfall events occurred. Run-off was collected on 23 Oct. and 6 Nov. 1996. Concentrations of P were very low regardless of poultry litter rate or cropping system (Table 4). No significant differences were observed for either rate or system.

Soil samples obtained from fall 1995 to spring 1996 indicated an increase of 105.7 mg/kg (ppm) of P in the surface 0-15 cm (0-6 in) of soil, when the litter rate was increased by four times (4X) the recommended (Fig. 9). There was also an increase at lower depths from this rate. Concentrations from commercial blend fertilizer was equal to that of the control.

A cropping system of spring vegetables followed by a fall clover crop decreased soil P in the surface 0-15 cm (0-6 in) by 40 mg/kg (ppm) (Fig. 10). The greatest increase was from a system of fall vegetable followed by a spring legume. The second highest was when a spring vegetable was followed by fall fallow. There were no real differences in concentration of P at the lower depths.

OBJECTIVE 4: Demonstrations.

Locations: Texas-Oklahoma

Texas:

Mr. Marty Baker, in cooperation with two County Agents, helped establish on-site demonstration plots with two local farmers. Mr. Hugh Soape, County Extension Agent, Cherokee County, Cooperative Extension Program – Prairie View A&M University (1890), helped in establishing a demonstration plot with Mr. Rollie Skinner, a black farmer. Sweet corn (`Merit’) was planted by the grower. Yield data were not obtained but was reported that more ears were harvested from the poultry litter grown sweetcorn than from the commercial fertilized corn.

After crop harvest, soil samples were obtained to determine residual P. In Fall 1996, the entire plot area was seeded to hairy vetch. Yield data were obtained in Fall 1996. The plot area that received poultry litter produced 1,520 kg/ha(1,356 lbs/ac) more of vetch dry matter than that receiving commercial fertilizer blend.

Mr. Greg Thomas, County Extension Agent, Nacogdoches County, Cooperative Extension Program – Prairie View A&M University (1890) helped in establishing the other demonstration plot on the George Millard farm. Mr. Millard averaged over 12.7 kg/plant (28 lbs) of tomatoes. Hairy vetch was not seeded in the Fall as planned due to a misunderstanding with his employees.

Oklahoma: See attachment-Oklahoma Report.

Participation Summary

Educational & Outreach Activities

Participation Summary

Education/outreach description:
Publications

Publications arising from this project to date are:

1. Haby, V. A., D. R. Earhart, G. Evers, and M. L. Baker. 1995. Land application of poultry litter in East Texas. Invited Tech. Poster. Paper published in Proceedings: Innovations and New Horizons in Livestock and Poultry Manure Management Conference. Vol. 1, pp 121-133.

2. Earhart, D. R., V. A. Haby, and M. L. Baker. 1996. Effect of cropping system on NO3-N concentration of surface run-off water and leachate from poultry litter application. Res. Ctr. Tech. Rpt. 96-2.

3. Earhart, D. R., V. A. Haby, and M. L. Baker. 1996. Cropping system and season of application of poultry litter affected residual soil P concentration. Res. Ctr. Tech. Rpt. 96-2.

4. Earhart, D. R., V. A. Haby, and M. L. Baker. 1996. Effect of poultry litter rate of application on residual soil NO3-N. Res. Ctr. Tech. Rpt. 96-2.

5. Earhart, D. R., V. A. Haby, and M. L. Baker. 1996. Effect of cropping system on residual soil P from poultry litter application. Res. Ctr. Tech. Rpt. 96-2.

6. Earhart, D. R., V. A. Haby, A. T. Leonard, and M. L. Baker. 1996. Cropping system and poultry litter effects on residual soil NO3-N and P. HortScience 31(5) 756.

7. Earhart, D. R., M. L. Baker, and V. A. Haby. 1997. Potential of cool-season legumes and a legume/grass mix for removing excess P. HortScience 32(4) 605.

8. Baker, M. L., D. R. Earhart, and V. A. Haby. 1997. Effect of cropping system on residual soil P from poultry litter application. HortScience 32(4) 604.

9. Borthick, Clydette, and Brian Kahn. 1997. Use of hairy vetch to manage soil phosphorus accumulation from poultry litter applications in a warm-season vegetable rotation. Vegetable Field Tour. Okla. Veg. Research Sta., Bixby Okla. June 26, 1997.

10. Borthick, Clydette, and Brian Kahn. 1997. Use of cowpea to manage soil phosphorus accumulation from poultry litter applications in a cool-season vegetable rotation. Vegetable Field Tour. Okla. Veg. Research Sta., Bixby Okla. June 26, 1997.

11. Earhart, D. R., M. L. Baker, and V. A. Haby. 1998. Soil phosphorus removal as a function of cropping system. HortScience 33(4):595.

12. Earhart, D. R., V. A. Haby, M. L. Baker, and J. T. Baker. 1998. Effect of poultry litter rate on residual soil P over a five season study period. Research Center Tech. Rpt. 98-2 pp. 15-16.

13. Earhart, D. R., V. A. Haby, M. L. Baker, and J. T. Baker. 1998. Effect of cropping system on residual soil P from poultry litter application over five seasons. Research Center Tech. Rpt. 98-2. pp. 17-18.

14. Baker, J. T., D. R. Earhart, M. L. Baker, F. J. Dainello, and V. A. Haby. 1998. Interaction of poultry litter, polyethylene mulch and floating row covers on triploid water melon production. Research Center Tech. Rpt. 98-2. pp 19-20.

15. Alsup, C., and B. A. Kahn. 1998. Use of cowpea to manage soil phosphorus accumulation from poultry litter application in a cool-season vegetable rotation. HortScience 33(4):591.

16. Alsup, Clydette M. 1998. Use of cowpea and vetch to manage accumulation of soil phosphorus from poultry litter applications in vegetable rotations. MS thesis. Oklahoma State Univ., Stillwater.

Education and Outreach

Two articles and one video have been completed on application of composted poultry litter for vegetable and forage farm systems. The articles were sent to area and state wide newspapers by Robert Burns, Extension Communications Specialist.

During the month of October 1996 Marty Baker gave presentations at several educational programs:

1. Eighty-two orchard owners, farmers and specialist met for the Texas Fruit Growers Association’s Annual Conference. Marty Baker presented information on topics relating to using poultry and animal waste for orchards and vegetable production.

2. Sixteen vegetable and fruit growers attended the Henderson County Produce Marketing Meeting. Marty gave a talk on utilizing poultry litter on vegetables and fruit farms.

3. One hundred and thirty-one participants in the Prairie View A&M University Cooperative Extension Program and Landowner’s Association’s Twelfth Annual Farmers Conference and Tours heard Marty’s program on aquaponics and utilizing compost and animal waste for growing ornamental and vegetable transplants as well as fingerling fish. Over one hundred participants were minority black men and women representing the agriculture community.

4. The State Extension Faculty Conference was held in October with a theme of “Sustainability: Ensuring a Prosperous Future”.

Other educational programs in July 1996 at which Marty presented information were:

1. Twenty-eight volunteer leaders and four extension agents received training in recycling animal waste, yard trimmings, MSW industrial, composting practices and vermiculture in Beaumont Texas. This training is worth several thousand dollars to the county for service hours.

2. Twenty-one farmers attended the Cherokee County’s farmers program on alternative crops utilizing composted poultry litter for special fall production. The meeting was planned by Hugh Soape, IFPP Agent.

Field days were held at the Texas A&M Agricultural Research and Extension Center at Overton, Texas each year (1995-1998) to emphasize the on-going research on sustainable agriculture and cultural practices. In both years, horticulture and livestock/forage field days were combined. The SARE/ACE project was highlighted each year.

Yearly grants of $4,000 from the Lake Fork Creek Hydrologic Unit Project have been received for enhancement of broiler litter studies and to prepare publications and farm cropping system plans to help alleviate environmental problems for Northeast Texas counties. Marty continues as an investigator in this project. His assigned efforts are in food production and farm system studies with emphasis on water quality and utilizing poultry and dairy waste.

Due to Marty’s efforts, he was elected chairman of the State Solid and Hazardous Waste Initiative Team, Texas Agricultural Extension Service, Texas A&M University System.

Extension specialists have conducted agent training sessions on educating farm owners/managers and the public concerning potential causes of non-point source contamination as a result of current management practices and how through BMP’S this can be reduced. Information gained has been shared with local, district, state and regional water authorities. Results have been disseminated through Extension videos, slide sets, circulars, result demonstration hand books, technical reports, and news print.

Electronic media outlets such as e-mail and agents’ on-line network to the district offices has provided an immediate dissemination of findings to all county agents. Networking groups for esusda.gov-sustainable working group has also received a forward copy of e-mail regarding waste management.

Extension and Experiment Station scientists along with demonstrators have conducted local, state and regional meetings on waste utilization and sustainable production of horticultural and forage crops. Information was also presented on water quality and sustainable soil productivity. Personnel of the Prairie View A&M University Extension Program – 1890 have disseminated information to small farm operators and limited resource producers. This was accomplished through field tours, meetings, circulars and one-on-one visits.

A sustainable web site has been established by Dr. Dan Lineberger, Dr. Nancy Roe, Mr. Marty Baker and other members of the SusAg Working Group. This group is made up of on and off campus personnel representing several disciplines from the Texas Agricultural Extension Service and Texas Agricultural Experiment Station.

Project Outcomes

Project outcomes:

OBJECTIVE 1: Rotational Cropping System.

Location: TAES-Overton, OSU-Bixby

TAES:

Dry matter yield of cool- and warm-season legumes was not influenced significantly by increased litter rate or commercial fertilizer. This is probably due to the fact that legumes have the ability to obtain N from the atmosphere and fix what N2 they need for growth. As litter rate is increased, legumes tend to remove more P under normal growing conditions. Residual soil P continues to increase as litter rate is increased. This increase has been shown to be reduced by a cropping system of planting a spring vegetable crop followed in the fall with a cool season legume crop such as crimson clover.

OSU: See attachment-Oklahoma Report

OBJECTIVE 2: Evaluation For P Uptake Efficiency.

TAES:

Dry matter yield between legume species varies greatly. Hairy vetch produced the highest yield and was more efficient at removing P than the other species. A mix of crimson clover and ryegrass was comparable in yield to hairy vetch. The mix combination was not as efficient at removing P as hairy vetch. Even though there was no significant difference in soil P concentration for any species at any depth, the lowest was with hairy vetch.

OBJECTIVE 3: Accumulation and Runoff.

TAES:

Residual soil P was reduced by a system of spring vegetables followed by crimson clover in the fall. The effect that different systems had on P concentrations in run-off water were very low. This could be attributed to incorporation of treatments which would tend to tie up P in the soil.

OBJECTIVE 4: Demonstrations.

TAES:

Poultry litter was found to increase both sweet corn and tomato yield from two demonstration plots on grower owned land in spring 1996. In fall 1996 dry matter yield of hairy vetch was increased from poultry litter application in the spring when compared to commercial fertilizer.

OSU: See attachment-Oklahoma Report

Impact of Results

Benefits to sustainable agriculture derived from this study include: (1) identifying new vegetable farming systems that are productive; (2) identification of strategies which reduce non-point source pollution and soil nutrient imbalances;(3) offering an opportunity for vegetable and other crop producers to adopt improved, environmentally sound management practices that do not sacrifice profitability; and (4) increasing the data base that can be used by regulatory agencies to enact policies that are environmentally and producer friendly. These practices will help to conserve natural resources as well as condition, maintain, and conserve our most important natural resources, soil and water. Poultry litter’s value as a fertilizer will be enhanced instead of becoming an increasing environmental problem.

Economic Analysis

Cooperative Efforts

Texas A&M University, Oklahoma State University, and Prairie View A&M University entered into a cooperative effort to research and demonstrate the environmental aspects of utilizing poultry litter in vegetable production systems. The systems studied involved litter rate and vegetable-legume cover crops. The responsibility of Texas A&M personnel was to evaluate litter application rate as well as cropping systems and their effects on P accumulation and run-off as well as screening legume species for P uptake efficiency. The main effort of Oklahoma State was to evaluate litter rate and cropping systems and their effect on P accumulation. All three universities have the responsibility of demonstrating litter use in cropping systems by commercial vegetable growers under grower conditions. Also, to provide outreach programs in order to educate growers on nutrient management strategies through environmentally sound best management practices.

Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.