Decreased foliar nitrogen and crop yield in organic rainfed almond trees during transition from reduced tillage to no-tillage in a dryland farming system

Sustainable farming practices can be beneficial or detrimental to crop production in the short-term, which will strongly determine their appeal to farmers. We evaluated the effects of several sustainable practices on soil properties, plant nutrition and ecophysiology and crop yield in a semiarid agroecosystern. A three-year randomised experiment was conducted in a rainfed almond grove where the initial soil management was reduced tillage. Two alternative treatments were evaluated: reduced tillage plus green manure and no-tillage. The following soil and plant parameters were measured once per year: soil organic carbon, total nitrogen and P-olsen: foliar N, P, delta C-13 and delta N-15 and crop yield. We found that soil bulk density increased significantly with no-tillage. Leaf delta N-15 was positively associated with soil fertility, foliar nutrient concentrations and crop yield across treatments. Leaf delta C-13, N-foliar and crop yield were strongly positively associated across treatments in every year of the study. Reduced tillage treatments displayed higher leaf delta N-15, delta C-13, N-foliar and crop yield than the no-tillage treatment, indicating a sharp decrease in the leaf nitrogen status and intrinsic water use efficiency of almond trees during the transition from reduced tillage to no-tillage. In semiarid agroecosystems where soils are prone to compaction, some tillage is required to maintain optimal crop production in rainfed almonds. (C) 2013 Elsevier B.V. All rights reserved.