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Use of Alkaline Stabilized Biosolids on Alfalfa and their Effect on the Cu/Mo Ratio in Alfalfa Tissue

Biosolids are commonly applied to pastures and crop fields. The trace element Mo, contained in biosolids, is of concern because in ruminant animals excessive Mo intake can induce Cu deficiency, a condition known as molybdenosis.

Introduction

The Cu:Mo ratio in the diet of ruminants should be above 2.0 for prevention of this disease. Lime stabilized biosolids are of particular concern because as soil pH increases, phytoavailability of Mo increases while that of Cu decreases.

Objectives

  • Examine the efficacy of alkaline stabilized biosolids (LB) as a lime substitute for alfalfa production on acidic soil.
  • Examine the effects of alkaline stabilized biosolids on alfalfa Cu and Mo uptake.

A 3 year field experiment was conducted in Lehigh Co, PA comparing LB with Agricultural Limestone (AL) for alfalfa production. LB were applied at 0, 0.5, 1.0, and 2.0 times the soil lime requirement and chemical fertilizer N and P were added to the AL treatments to match N and P supplied by LB. All treatments were reapplied in the second year.

Biosolids are commonly applied to pastures and crop fields. The trace element Mo, contained in biosolids, is of concern because in ruminant animals excessive Mo intake can induce Cu deficiency, a condition known as molybdenosis. The Cu:Mo ratio in the diet of ruminants should be above 2.0 for prevention of this disease. Lime stabilized biosolids are of particular concern because as soil pH increases, phytoavailability of Mo increases while that of Cu decreases.

Treatments

  1. Control (no soil amendments)
  2. Positive control (recommended rates of Ag lime and fertilizer)
  3. Limed Biosolids (LB) at 0.5x LR (9 Mt ha-1; 39, 60, 28 kg ha-1 N, P ,K)
  4. Limed Biosolids (LB) at 1.0x LR (18 Mt ha-1;77, 120, 56 kg ha-1 N, P,K)
  5. Limed Biosolids (LB) at 2.0x LR (36 Mt ha-1 ; 154, 240, 111 kg ha-1 N, P, K)
  6. Ag lime (AL) at 0.5x LR (2.2 Mt ha-1; +N, P, K to match LB 0.5 rate)
  7. Ag lime (AL) at 1.0x LR (4.5 Mt ha-1; +N, P, K to match LB 1.0 rate)
  8. Ag lime (AL) at 2.0x LR (9.0 Mt ha-1; +N, P, K to match LB 2.0 rate)