Maize and sunflower yields and soil changes after five years of organic fertilization in the semi-arid region of Paraiba, Brazil

Effects of annual organic fertilization on maize and sunflower yields and on physical and chemical characteristics of a Fluvisol were evaluated in the semiarid area of Paraiba state, from 2007 to 2011. The experiment was a block design in a 4 x 2 factorial arrangement, corresponding to one control and three fertilizer treatments (cattle manure and Gliricidia sepium and Croton sonderianus prunings) and two application procedures (soil surface or incorporated in the 0-10 cm layer), with four replications. Maize was grown in the first 3 years and then sunflower was grown for 2 years. Grain and straw yields increased with fertilization, especially in the years of good rains (maize, 0-61%, reaching 3.4 Mg ha(-1) of grain; sunflower, 48-112%, reaching 1.4 Mg ha(-1) of achenes), differing only slightly between fertilizer types and form of application. All fertilizers incorporated for 5 years reduced water infiltration time (20-50%), but only manure and G. sepium reduced soil bulk density (about 10%) and increased soil porosity (7-10%). Manure increased soil pH (0.7-1.0 units). Surface application of manure and C. sonderianus increased soil organic matter (28 and 72%) and phosphorus concentrations (about 70%). We suggest that, in sites with soil physical problems (slow water infiltration, high soil compaction, and low porosity), organic fertilizers may lead to better responses if incorporated into the soil. If there is a need for greater improvement of soil organic matter, nutrients and water conservation, surface applied organic manure and C. sonderianus may be a better management practice.