Effects of soil amendments on crusting, seedling emergence and yield of onion, tomatoes and peppers.

Abstract

The effects of sulfur-containing amendments (H₂SO₄,Al₂(SO₄)₃ and gypsum) or crust formation, soil chemical properties, seedling emergence and yields of onions (Allium cepa), tomatoes (Lycopersicum esculentum) and chili peppers (Capsicum sp.) were studied on a Pima clay loam soil. Treatments were surface applied on a strip above the seeds. The chemicals influenced the penetrometer index, soil-pH, electrical conductivity, DPTA-extractable soil Fe, Cu, Zn, Mu and seedling emergence in two greenhouse experiments. Gypsum and H₂SO₄ increased seedling emergence while Al₂(SO₄)₃ reduced the soil-pH and EC more than H₂SO₄ and gypsum. Based upon penetrometer readings, H₂SO₄ was the best anti-crusting agent tested followed by gypsum and Al₂(SO₄)₃. At the end of the study, all soil samples were very low in KCl extractable Al, showing that Al toxicity was not responsible for seedling damage. Gypsum decreased levels of Mn and Zn but did not affect Fe and Cu. Al₂(SO₄)₃ increased Fe and Zn, decreased Cu but did not affect Mn. H₂SO₄ did not affect extractable Mn, Cu, Zn and Fe levels. In a field study using two water qualities at Safford, gypsum produced the most tomato seedlings whereas Al₂(SO₄)₃ and H₂SO₄ produced the least. Onion stand counts were not affected by the chemicals with either water. Gypsum, H₂SO₄ and Al₂(SO₄)₃ polymer produced the highest pepper stand counts with the saltier water but there were no differences with lower salt water. Tomatoes produced the highest yield with gypsum and lowest with H₂SO₄ and Al₂(SO₄)₃ with saltier water. With lower salt water, gypsum produced highest yield, followed by the H₂SO₄. Both H₂SO₄ treatments produce low yields. Onions showed no treatment response under lower salt water, while with saltier water, gypsum and H₂SO₄ produced the highest yields. Pepper yields were not affected by amendments with the lower salt water. Al₂(SO₄)₃ polymer, H₂SO₄ and gypsum increased yields with the saltier water. Varieties of peppers and tomatoes produced different yields in response to water quality in a supplementary field study.