Soil-Applied Nitrogen and Composted Manure Effects on Soybean Hay Quality and Grain Yield

ABSTRACT

Grain yield in many soybean experiments fails to respond to fertilizer nitrogen (N). A few positive responses have been reported when soybean were grown in the southern U.S., when N was applied near flowering and when biosolids were added. In a previous study, low N concentrations of soybean forage in north Texas on a high pH calcareous soil were reported and thus, we suspected a N nutrition problem. Consequently, we initiated this study to determine whether selected preplant N sources broadcast and incorporated into a Houston Black clay (fine, smectitic, thermic Udic Haplusterts) might increase forage N concentration, forage yield, or soybean grain yield. In 2003, N was applied as ammonium nitrate (NH₄NO₃, AN) up to 112 kg N ha^{− 1} and dairy manure compost (DMC) was applied at rates of 4.9, 9.9, 15.0, and 19.9 Mg ha^{− 1}. The DMC contained 5.9, 2.6, and 6.7 g kg^{− 1} of total N, P, and K, respectively; thus DMC added 29 to 116 kg N ha^{− 1}. In 2004, AN was applied at rates of 112 and 224 kg N ha^{− 1} and DMC was applied at 28 and 57 Mg ha^{− 1}; thus, DMC added 168 to 335 kg N ha^{− 1}. In another 2004 test, biosolids, a biosolids/municipal yard waste compost mixture (BYWC), and AN were compared. The biosolids contained 31, 18, and 2.9 g kg^{− 1} total N, P, and K, respectively. The BYWC mixture contained 8.8, 6.1, and 3.4 g kg^{− 1} of total N, P, and K, respectively. Biosolids were applied at 10 Mg ha^{− 1} (310 kg N ha^{− 1}), BYWC was applied at 58 Mg ha^{− 1} (510 kg N ha^{− 1}), and AN up to 224 kg N ha^{− 1}. None of the soil treatments increased soybean grain yield or forage yield although AN slightly increased forage N concentration in 2003.

Keywords:

• forage soybean
• manure
• biosolids
• nitrogen response
• digestibility

Notes

^† DMC, dairy manure compost.

^‡ BYWC, biosolids/municipal yard waste compost.

^§ ns indicates that yields were not significantly different among treatments within a year.