Experiment 301, Long-Term Application of Biosolids in Winter Wheat, Stillwater, OK

Experiment 301: Continuous Application of Biosolids in Winter Wheat Production, 1994-2004

Summary

· From 1994 to 2004, AN treatments at the same N rate resulted in significantly greater grain yields when compared to biosolids treatments.

· Poor stand and weed pressure adversely affected yields in 1995 and 1996

· In 5 of 11 years applying 160 lb N/ac resulted in increased yields compared to 80 lb/ac

· RI_NDVIpredicted RI_HARVEST in 3 of 6 years, underestimating in the other 3

References

Gavi, F., W.R. Raun, N.T. Basta, and G.V. Johnson. 1997. Effect of sewage sludge and ammonium nitrate on wheat yield and soil profile inorganic nitrogen accumulation. J. Plant Nutr. 20 (2&3): 203-218.

Mullen, R. W., W.R. Raun, N.T. Basta, J.L. Schroder, and K.W. Freeman. 2004. Effect of long-term application of biosolids on molybdenum content and quality of winter wheat forage. J. Plant Nutr. (in press).

Abstract

Environmentally sound management practices for sewage sludge in grain crop production systems are becoming increasingly important. The objectives of this study were to compare N rates of sewage sludge and ammonium nitrate on yield and heavy metal uptake in winter wheat (Triticum aestivum L.). One field experiment was established in 1993 that evaluated six N rates (0 to 538 kg ha^-1 yr^-1) as dry anaerobically digested sewage sludge and ammonium nitrate. Lime application in 1993 (8.96 Mg ha^-1), 1999 (8.96 Mg ha^-1) and 2000 (12.99 Mg ha^-1) was also evaluated. In general, wheat yields peaked at the 180 kg N ha^-1 rate when N was applied as either sewage sludge or ammonium nitrate. However, wheat grain yields were significantly higher using ammonium nitrate when compared to sewage sludge at comparable rates. Averaged over this seven year period, ammonium nitrate treatments resulted in 28.1 bu/ac (1.9 Mg/ha) while sewage sludge resulted in 20.2 bu/ac (1.4 Mg/ha)(both averaged over N rates). Fertilizer N immobilization was expected to be high in the first few years since this site was previously in native bermudagrass (Cynodon dactylon L.). Following 2-3 years of applying sewage sludge, we expected to achieve the same yields at comparable rates as that using ammonium nitrate. Because ammonium nitrate treatments continue to produce significantly higher yields (following 7 years) when compared to sewage sludge, either N mineralization rates are markedly lower than that previously thought (21% for sewage sludge), or the soil-plant system has yet to achieve equilibrium. Molybdenum concentrations in wheat forage at Feekes growth stage 4 were significantly higher in sewage sludge treated plots when compared to ammonium nitrate. Alternatively, Cu and Fe levels did not differ in wheat forage as a function of N source (sewage sludge versus ammonium nitrate). The Cu to Mo ratio in the wheat forage was above 2 for all treatments. When Cu:Mo ratios are less than 2 in wheat forage, cattle can develop Cu deficiencies. When lime was applied, forage Mo levels were dramatically higher for sewage sludge plots as compared to ammonium nitrate.

Table 1. Treatment structure and grain yield means (kg/ha), 1994-2004, Stillwater, OK.

TRT	Source	N-rate	1994	1995	1996	1997	1998	1999	2000	2001	2002	2003	2004	Mean
1	ck	0	464	499	613	1128	1934	908	924	1246	1677	1621	2157	1197
2	ck	0	378	520	575	1288	1611	903	975	1075	834	1505	1888	1050
3	ss	40	527	571	728	1558	2379	948	1310	1685	1753	2357	2921	1522
4	ss	80	617	574	657	1515	2243	1069	1498	1574	2056	2398	3033	1567
5	ss	160	886	569	1234	1400	3050	1362	1576	1982	1972	2754	3426	1846
6	ss	240	1038	611	919	1390	2832	965	1234	1778	1871	1505	3734	1637
7	ss	480	1505	1027	822	1458	3604	1834	1923	1542	1972	2622	3651	1996
8	an	40	1782	620	339	1369	2055	904	1719	1387	1905	1662	2530	1479
9	an	80	1739	906	512	1763	2863	1608	2887	1843	2731	3581	3818	2205
10	an	160	1921	1196	666	2177	3442	2369	3304	2271	2596	4342	4260	2595
11	an	240	2589	1419	536	2351	3041	2890	2785	1627	1551	3382	3382	2323
12	an	480	2337	1282	557	2557	3106	2477	2052	1791	1728	2936	3416	2204
13	ssl	480	1669	1052	880	1630	3730	2602	1569	1987	2225	3366	4515	2293
14	anl	480	2187	1326	782	2843	3711	2860	2212	1825	2115	4466	4822	2650
	Mean		1442	944	788	1745	2829	1693	1877	1687	1928	2750	3397	1897
	SS		914	670	872	1464	2822	1236	1508	1712	1925	2327	3353	1714
	AN		2073	1085	522	2044	2901	2050	2549	1784	2102	3181	3481	2161
			1159	414	-350	579	80	814	1041	71	177	853	128	447

L - lime applied at a rate of 8960 kg/ha (4 tons/acre) in the fall of 1993
L – lime applied at a rate of 8960 kg/ha (4 tons/acre) in the fall of 1999 (87% ECCE)
L - lime applied at a rate of 12,992 kg/ha (5.8 tons/acre) in the fall of 2000 (85% ECCE)
SS - sewage sludge obtained from the City of Stillwater
AN - ammonium nitrate (34-0-0)
SED - standard error of the difference between two equally replicated means
CV - coefficient of variation, %

Table 2. Total nitrogen and moisture content of Stillwater sewage sludge, 1993 to 2000.

1993	1994	1995	1996	1997	1998	1999	2000	Avg.
Total N, %
2.02	1.74	1.97	2.73	2.42	2.43	2.02	2.44	2.22
Moisture, %
60	35	59	na	55	46	45	17	45

From 1994 to 1997, AN treatments at the same N rate resulted in significantly greater grain yields when compared to sewage sludge.
Poor stand and weed pressure adversely affected yields in 1996
By 1998, no differences in grain yield could be detected between AN and SS treatments
In 1999, SS treatments had significantly lower yields when compared to the same N rates using AN

Annually applied biosolids, fall of 1993 to 2002, Efaw Experiment Station, Stillwater, OK 2002.

Annually applied biosolids, picture taken in the spring of 1996, Efaw Experiment Station, Stillwater, OK 2002.

Dr. N.T. Basta, Presentation, 1999